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The effect of head compression on FHR, brain metabolism and function
Abstract
The effect of fetal head compression on heart rate, cerebral metabolism and function was studied in 30 sheep experiments. Cerebral oxygen consumption decreased markedly, as cerebral blood flow was significantly impaired by the increase in intracerebral pressure and vascular resistance. A fetal bradycardia or tachycardia occurred in 76% of the experiments. The fetal EEG showed a drop-out of faster frequencies, slowing and a decrease in amplitude prior to the onset of an isoelectric (flat) stage. All parameters recovered rapidly after the episode of cerebral ischemia caused by head compression. © 1972 The American College of Obstetricians and Gynecologists.
... At the malities at one year of age increased. same time, a slowing in fetal EEG was observed Nowadays the graphic recording of FHR may be [12], In human fetuses, similar changes in the obtained by external methods (ultrasounds, EEG were recorded during labor with ruptured phonocardiography) not requiring amniotomy. membranes [7] ; these EEG changes coincided Monitoring of the f etus during labor can be perwith the peak of uterine contractions that caused formed with intact membranes. ...
... Type II dips are not further analyzed in this paper. Evidence obtained from clinical observations [l, 6,13, 19, 20] indicates that type I dips may be associated with the uneven compression and deformation of the fetal head, which may cause EEG alterations [7], cerebral birth trauma (21) and neurological sequelae [15] , Experimentation in animals [12,14] shows that compression of the fetal head reduces cerebral blood flow and oxygen availability to the brain, altering the EEG and increasing vagal tone with the consequent rapid fall in FHR. Keywords: Bag of waters, compression of fetal head, dips — early and late, fetal heart rate, labor — monitoring of " nuchal cord, rupture of membranes, uterine contractions. ...
... Aus klinischen Beobachtungen [l, 6,13,19, 20] was zu EEG-Veränderungen , zerebralem Geburtstrauma und zu neurologischen Folgeerkrankungen führen kann [7, 21,15]. Tierversuche [12,14] zeigen, daß die Kompression des fetalen Kopfes die Blut-und Sauerstoffversorgung des Gehirns vermindert , wodurch es zu EEG-Veränderungen und einem Anstieg des Vagus-Tonus kommt mit raschem Abfall der fetalen Herzfrequenz. All diese Tatsachen lassen es ratsam erscheinen, die allgemeine geburtshilfliche es t dejä connu que la production de Dips Type I par les contractions uterines est significativement plus haute apres Pamniotomie qu'avant la meme. ...
The study is made in 37 pregnant women without known complications and in whom labor starts spontaneously at term and progresses without need of oxytocic, analgesic or other drugs. In 17 of these labors, the membranes are ruptured artificially when cervical dilatation reaches 5 cm (early amniotomy). In the other 20 labors membranes remain intact at least until full cervical dilatation is obtained. The decision to perform early amniotomy is made at random. In all 37 labors intrauterine pressure and fetal heart rate (FHR) are graphically recorded. When membranes are intact, FHR is recorded by means of ultrasound. There are no significant differences between both groups of labors in the duration of labor and in birthweight, cephalic perimeter and Apgar score of the neonates. The incidence of type I dips in a given group of labors is expressed by the percentage of uterine contractions which produced type I dips. For this calculation all the contractions recorded in the several labors of the group are pooled together. The significance of the difference in the incidence of type I dips between the two groups is determined by a nonparametric statistical test. The incidence of type I dips is low or nil when the membranes remain intact until a few minutes before delivery. If the rupture occurs late, when the fetal head is engaged, a high incidence of type I dips is recorded after the rupture. After early amniotomy, made before head engagement, the incidence of type I dips is low; as the head engages the incidence increases. The influence of 3 factors on the incidence of type I dips is analyzed quantitatively: status of the membranes (intact or ruptured); station of the fetal head (before or after engagement); loop of cord around the fetal neck (present or absent). During the first stage of labor the incidence of type I dips is significantly lower in the group of labors with intact membranes (3%) than in that with early amniotomy (21%). This result agrees with the hypothesis that the bag of waters protects the fetal head from the uneven compression received during uterine contraction. A similar result is found when the incidence of type I dips is studied in the period of labors before engagement of the head and also in the period after engagement. In both conditions the incidence of type I dips is significantly lower in labors with intact membranes than in those with early amniotomy. This finding suggests that the protective effect of the bag of waters is present both before and after head engagement. In the group of labors with ruptured membranes, the incidence is significantly higher after the head is engaged than before engagement indicating that in absence of the bag of waters the engagement greatly facilitates the production of type I dips. A similar comparison made in the group of labors with intact membranes shows no significant difference before and after engagement of the head, confirming the protection provided by the unruptured membranes even when the head is engaged. No significant influence of a loop of cord around the fetal neck on the incidence of type I dips is found in either group. The incidence of type II dips ('late deceleration', 10) is very low (less than 2%) in all groups, in keeping with the excellent condition of all neonates. Type II dips are not further analyzed. Evidence obtained from clinical observations indicates that type I dips may be associated with the uneven compression and deformation of the fetal head, which may cause EEG alterations, cerebral birth trauma and neurological sequelae. Experimentation in animals shows that compression of the fetal head reduces cerebral blood flow and oxygen availability to the brain, altering the EEG and increasing vagal tone with the consequent rapid fall in FHR. All these facts make it advisable to reevaluate the common obstetrical practice of rupturing membranes artificially early in the first stage of labor, as a routine procedure in the management of labor.
... Another study of mechanically applied extracranial pressure by Mann et al used a pediatric rib retractor to apply high forces to the fetal lamb skull. 20 The fetal lamb with its fused cranial sutures is likely a poor model for these studies. The relevance of these nonphysiologic animal models is unclear, but it is included for completeness. ...
Objective During labor the fetal head is subjected to pressure related to uterine contractions and maternal pushing. Here we systematically review what is known about fetal head compression and its effects on fetal intracranial pressure, oxygenation, blood flow and cerebral function, and the plausibility that it might cause isolated fetal brain injury.
Study Design Systematic review of intrapartum fetal head compression and fetal brain injury in accordance with the MOOSE methodology. The PubMed database was searched using a combination of the terms “fetal,” “head,” “cranial,” “extracranial,” “pressure,” and “compression.” Additional references were obtained using multiple strategies. Results were evaluated, and relevant studies encompassing animal and human data using several approaches are summarized in this review.
Results Studies support a significant increase in fetal extracranial pressure with contractions and pushing. However, available data do not support a concomitant significant relative increase in intracranial pressure, a reduction in cerebral circulation or oxygenation, or an impact on cerebral function.
Conclusion A review of the literature indicates that fetal intracranial pressure is well protected from extracranial forces. Available data do not support intrapartum fetal extracranial pressure as a cause of fetal brain injury.
Precis The fetal brain is relatively unaffected by intrapartum fetal head compression.
... Recently, focus has begun to shift from concerns about hypoxia to ischemia, and the idea that the fetal brain can be injured during labor by ischemia from excessive intracranial pressure even in the absence of severe hypoxia has piqued the interest of investigators [67,69,70]. In fact, some studies indicate that at least half of babies diagnosed with neonatal encephalopathy show no evidence of severe asphyxia at birth [71,72], yet imaging studies are consistent with acute ischemic injury [73]. ...
In the 1930s, investigators in the US, Germany and Switzerland made the first attempts to quantify the course of labor in a clinically meaningful way. They emphasized the rupture of membranes as a pivotal event governing labor progress. Attention was also placed on the total number of contractions as a guide to normality. Beginning in the 1950s, Friedman determined that changes in cervical dilatation and fetal station over time were the most useful parameters for the assessment of labor progress. He showed all normal labors had similar patterns of dilatation and descent, differing only in the durations and slopes of their component parts. These observations led to the formulation of criteria that elevated the assessment of labor from a rather arbitrary exercise to one guided by scientific objectivity. Researchers worldwide confirmed the basic nature of labor curves and validated their functionality. This system allows us to quantify the effects of parity, analgesia, maternal obesity, prior cesarean, maternal age, and fetal presentation and position on labor. It permits analysis of outcomes associated with labor aberrations, quantifies the effectiveness of treatments and assesses the need for cesarean delivery. Also, dysfunctional labor patterns serve as indicators of short- and long-term risks to offspring. We still lack the necessary translational research to link the physiologic manifestations of uterine contractility with changes in dilatation and descent. Recent efforts to interpret electrohysterographic patterns hold promise in this regard, as does preliminary exploration into the molecular basis of dysfunctional labor. For now, the clinician is best served by a system of labor assessment proposed more than 60 years ago and embellished upon in considerable detail since.
... Similarly, head compression in fetal sheep with a modified rib retractor was only associated with decelerations in 37% of cases. When a deceleration did occur, it was again associated with reduced cerebral blood flow and profound suppression of fetal electroencephalographic activity (Mann et al. 1972). ...
A distinctive pattern of recurrent rapid falls in fetal heart rate, called decelerations, are commonly associated with uterine contractions during labour. These brief decelerations are mediated by vagal activation. The reflex triggering this vagal response has been variably attributed to a mechanoreceptor response to fetal head compression, to baroreflex activation following increased blood pressure during umbilical cord compression, and/or a Bezold-Jarisch reflex response to reduced venous return from the placenta. Although these complex explanations are still widespread today, there is no consistent evidence that they are common during labour. Instead, the only mechanism that has been systematically investigated, proven to be reliably active during labour and, crucially, capable of producing rapid decelerations is the peripheral chemoreflex. The peripheral chemoreflex is triggered by transient periods of asphyxia that are a normal phenomenon associated with all uterine contractions. This should not cause concern as the healthy fetus has a remarkable ability to adapt to these repeated but short periods of asphyxia. This means that the healthy fetus is typically not at risk of hypotension and injury during uncomplicated labour even during repeated brief decelerations. The physiologically incorrect theories surrounding decelerations that ignore the natural occurrence of repeated asphyxia likely gained widespread support to help explain why many babies are born healthy despite repeated decelerations during labour. We propose that a unified and physiological understanding of intrapartum decelerations that accepts the true nature of labour is critical to improve interpretation of intrapartum fetal heart rate patterns.
... The latter findings are in agreement with the previous descriptions of slow-wave sleep in humans and horses. [22][23][24] In human infants, slow-wave activity (detected via EEG), 25 deceleration in heart rate, and diminished brain metabolism 26 are evident when increased pressure is applied by maternal pushing in the second stage of labor (similar to the pressure exerted on the foals of the present study during restraint). However, the methods and design of our study preclude making further comparisons regarding these apparent similarities. ...
Objective:
To test the hypothesis that application of a rope restraint device would result in behavioral, electroencephalographic, and humoral changes consistent with sleep and analgesia in neonatal foals.
Animals:
8 healthy neonatal foals.
Procedures:
Following acclimatization to experimental conditions, each foal underwent a series of assessments before and during or at the end of a period of restraint via application of a restraint device (soft linen rope). Assessments included measurements of heart and respiratory rates, rectal temperature, and circulating β-endorphin and steroid hormone concentrations and evaluations of mentation and body position (behavior), electroencephalographic patterns, and pain tolerance.
Results:
All foals were lively with apparently normal behavior prior to restraint. During application of the restraint device, foals assumed lateral recumbency with relaxed, somnolent behavior. Heart and respiratory rates and rectal temperature uniformly decreased as a result of the procedure. Electroencephalographic recordings (completed for 3 foals only) revealed patterns consistent with slow wave sleep. Plasma ACTH, dehydroepiandrosterone sulfate, and androstenedione concentrations significantly increased during restraint, compared with prerestraint values. The foals' tolerance to noxious stimuli significantly increased during restraint; however, this was independent of the concentration of circulating β-endorphin.
Conclusions and clinical relevance:
In neonatal foals, the evaluated form of restraint resulted in a decrease in heart and respiratory rates and rectal temperature. Squeeze-induced somnolence may resemble the effects of compression of the fetus in the birth canal and lead to inhibition of voluntary activity. Use of this technique to safely restrain neonatal foals during minor procedures warrants further evaluation.
... The Stimulus could be initiated by increased pressure on the vagus center or by a baroceptor response via vagus nerve to the systemic hyper-tension also evoked by high intracranial pressure [7]. Neural mechanisms are probably the first to cause the bradycardia, but there is experimental evidence of a biochemical change relating to the lowering of brain oxygenation including the vagal nuclei which prolongs the neural component [11, 13, 15]. It therefore is reasonable to expect a variety of shapes of cardiacdecelerationsdependingon the variations in the Stimuli. ...
... During labour the fetal head is subjected to considerable compression [16] and we have previously reported that uterine contractions are associated with significant changes in [Hbtot] and cerebral blood volume (CBV) [9]. The pattern that we have most frequently observed is one of a transient reduction in CBV synchronous with each uterine contraction but we have previously noted that a minority of fetuses demonstrated a rise in CBV with uterine contractions [8,9]. ...
To test the hypothesis that a nuchal cord has a significant effect upon fetal cerebral haemodynamics and oxygenation during labour.
A specially designed optical probe was inserted through the dilated cervix and placed against the scalp of 37 fetuses during labour in a teaching hospital obstetric unit. Changes in total cerebral haemoglobin concentration were measured continuously together with fetal heart rate and uterine contraction frequency during the first and second stages.
At birth 11 fetuses (30%) were noted to have a nuchal cord (cord around the neck). For these, significantly more contractions were associated with an increase in total cerebral haemoglobin concentration when compared with the control fetuses without a nuchal cord (40.2% (S.D.19.5) vs 5.9% (S.D.7.1), P < 0.001). A significantly greater number of variable decelerations was found in the nuchal cord group (4 per 30 min vs. 2 per 30 min in the controls) (P < 0.01). There was no significant difference between mean cerebral oxygen saturation determined at the end of the first stage of labour, which was 47.0% (S.D.13.3) and 50.1% (S.D.11.8) for the nuchal cord and control groups, respectively.
A nuchal cord was associated with a significant increase in cerebral blood volume during uterine contractions, without any significant effect upon cerebral oxygenation.
... dramatically altering cerebral vascular tone at term, and during the process of birth. Parturition may be associated with increased intracranial pressure with a reduction in transmural pressure (Mann et al. 1972; Helou et al. 1994), and the potential to reduce CBF. Experiments conducted in utero have shown that raising intracranial pressure decreases cerebrovascular resistance in the nearterm (132 d) but not mid-gestation (92 d) fetus. ...
We have shown recently that development from neonatal to adult life affects cerebrovascular tone of mouse cerebral arteries through endothelium-derived vasodilatory mechanisms. The current study tested the hypothesis that development from fetal to adult life affects cerebral artery vascular smooth muscle (VSM) [Ca(2+)](i) sensitivity and tone through a mechanism partially dependent upon endothelium-dependent signalling. In pressurized resistance sized cerebral arteries ( approximately 150 microm) from preterm (95 +/- 2 days gestation (95 d)) and near-term (140 +/- 2 days gestation (140 d)) fetuses, and non-pregnant adults, we measured vascular diameter (microm) and [Ca(2+)](i) (nm) as a function of intravascular pressure. We repeated these studies in the presence of inhibition of nitric oxide synthase (NOS; with l-NAME), cyclo-oxygenase (COX; with indomethacin) and endothelium removal (E-). Cerebrovasculature tone (E+) was greater in arteries from 95 d fetuses and adults compared to 140 d sheep. Ca(2+) sensitivity was similar in 95 d fetuses and adults, but much lower in 140 d fetuses. Removal of endothelium resulted in a reduction in lumen diameter as a function of pressure (greater tone) in all treatment groups. [Ca(2+)](i) sensitivity differences among groups were magnified after E-. NOS inhibition decreased diameter as a function of pressure in each age group, with a significant increase in [Ca(2+)](i) to pressure ratio only in the 140 d fetuses. Indomethacin increased tone and increased [Ca(2+)](i) in the 140 d fetuses, but not the other age groups. Development from near-term to adulthood uncovered an interaction between NOS- and COX-sensitive substances that functioned to modulate artery diameter but not [Ca(2+)](i). This study suggests that development is associated with significant alterations in cerebral vascular smooth muscle (VSM), endothelium, NOS and COX responses to intravascular pressure. We speculate that these changes have important implications in the regulation of cerebral blood flow in the developing organism.
Fetal heart tracings (FHTs) are useful as a window into the oxygenation status of the fetal brain. Patterns in the FHT reflect the oxygen status of the fetal brain. Fetal adaptive response to progressive hypoxemia and acidosis are detectable and produce recognizable patterns in the fetal heart rate. The basic physiology and adaptive responses that regulate the fetal heart rate and physiological fetal adaptations to stress as reflected in the FHTs are described. Mechanisms of oxygen delivery to the fetus including ways in which those mechanisms can be disrupted are reviewed.
During the course of pregnancy, the mother undergoes major physiologic and metabolic adaptations to accommodate the requirements of the developing fetus and to prepare for subsequent delivery, lactation, and care for her newborn infant. To some, to speak of the history of maternal physiology, in a volume devoted to the physiology of the fetus and newborn infant, may appear to be a contradiction in terms. However, as the fetus constitutes a portion of the maternal-placental-fetal “complex” or “unit” (Diczfalusy 1964), and its growth and development would be impossible without the mother, it suggests a rationale for this consideration. In addition, because optimal fetal developmental cannot occur in the absence of profound changes in the physiologic function of almost each of the maternal organ systems, metabolic, cardiovascular, respiratory, renal, neurohumoral, and others, such consideration is vital. The organs of the female reproductive system are among the most dynamic tissues in the human body. Even in the absence of pregnancy, from puberty to menopause, these undergo repeated cycles of growth and involution. To attain such plasticity, the reproductive tissues must respond to blood-borne signals (hormones, growth factors, and cytokines), as well as physical forces (mechanical and osmotic).
In a population of high-risk patients who had continuous “direct” monitoring during labor, 598 (46%) had no decelerations during the first stage, while 247 (19%) had presented early decelerations before completion of dilatation. The clinical characteristics, the fetal heart rate (FHR) baseline alterations, and neonatal outcome were compared between these two groups: there were no differences in any of the aspects evaluated, except that there was transient tachycardia more often among the early-decelerations group. The patients who had no decelerations were subdivided into vaginal deliveries and cesarean deliveries, and the same parameters were compared again: the cesarean section group had longer recordings and more contractions, lower Apgar 1 and 5 minute scores, and higher incidences of Apgar scores ≤ 6 at 1 minute, while all other aspects were similar. A possible explanation was that 82% of cesarean sections were done under general anesthesia and only 3% of vaginal deliveries. The implication of ruptured membranes in the etiology of early decelerations was extensively reviewed and discussed in view of these findings. It is concluded that amniotomy does not seem a maneuver deleterious to the fetal well-being.
A total of 1,503 vaginal deliveries with the Shute parallel forceps during a 10 year period are analyzed as to the risk of instrumental damage. In this series, 35 infants died intrapartum or neonatally. Eliminating all deaths from unrelated causes, three remain in which the forceps could possibly have been implicated. Investigation of these, however, revealed in each case the presence of other concomitant and potentially lethal factors, none of which could be completely ruled out as the primary cause of fetal death. Each of the three cases is discussed in detail. We conclude from our series that the Shute forceps is useful in the delivery of premature infants, but should be employed for this maneuver only by very experienced operators. In these cases, midforceps should be performed only for critical indications. The risk of damage with parallel forceps deliveries from the pelvic floor is minimal if decision for operation is based on cardiotocographic criteria, and under favorable degrees of oxygenation. In the delivery of the immature infants, the parallel forceps can, in fact, hardly be superseded by any other instrument because of its unique controlled protection of the fragile fetal head from even the pressures of the birth canal. Delivery with the Shute forceps can be performed effectively under pudendal block or local infiltration anesthesia.
The rapid slowdown of the FHR tracing occurring simultaneously with a uterine contraction followed by an equally rapid recovery after an instantaneous low point is called early deceleration of the FHR. It has also been called dip I or cephalic dip. The time relationship between the intrauterine pressure changes and the fall in FHR is crucial to properly classify an alteration manifested as deceleration below the baseline of an otherwise normal looking tracing. The descending arm of the FHR coincides synchronically with the ascending part of the UC tracing, and its lowest point corresponds with the peak of the contraction (Figure 13-1). Following this moment, as the uterus relaxes and the intrauterine pressure falls, there is a rapid recovery of the FHR toward the baseline. The complete cycle of deceleration acquires the shape of a sharp V when the tracing is run at the standard 1 cm/min paper speed (Figures 13-2 and 13-3), and it is slightly U-shaped when the paper runs at 3 cm/min (Figure 13-4).
Die Geburt des Menschen, die in 96% der Fälle aus der Schädellage erfolgt (Martius 1977), ist ein komplizierter Vorgang, der sich aus der besonderen Form des menschlichen Geburtskanals und den relativ großen Kopfmaßen des Kindes erklärt. Der aufrechte Gang des Menschen beeinflußte im Laufe der Evolution die Ausformung des Beckenskeletts und führte zur Verstärkung des Muskel- und Bindegewebes des Beckenbodens (Stewart 1984 a). Es resultierte ein nach vorne gebogener Geburtskanal, dessen Ausgang von festem Weichteilgewebe umgeben wird. Parallel hierzu vergrößerte sich das Gehirnvolumen des Feten. Die Folge ist ein komplexer Geburtsmechanismus, der eine Beugung und Rotation des kindlichen Kopfes bei der Passage durch den Beckenkanal erforderlich macht. Leicht kann es hierbei zu Regelwidrigkeiten kommen, die entweder aus einem Mißverhältnis zwischen dem Raumangebot des mütterlichen Beckens und der kindlichen Größe oder aus einer unzureichenden Anpassung des kindlichen Kopfes an die räumlichen Bedingungen des Geburtskanals entstehen. So war es seit jeher eine wichtige Aufgabe der Geburtshilfe, die sich hieraus ergebenden Gefahren für Mutter und Kind abzuwenden.
Fetal sheep brain wave changes during recovery from operations and fetal heart rate and brain wave changes during acute maternal hemorrhage are described. During the first 24 hours after operation, there was a change in fetal brain wave with increasing amplitudes and faster frequencies of brain waves. A fully recovered EEG was not present for at least 24 hours. During acute maternal hemorrhage the heart changes were primarily those of heart rate irregularity with bradycardia being the most common pattern. Brain wave changes occurred early and progressed through a pattern of slower frequencies and decreasing amplitudes to an isoelectric state which always preceded terminal bradycardia.
The authors report their experiences in recording fœtal E.E.Gs at the time of labour, based on 140 studies. They studied normal E.E.Gs and emphasise the existence of a sleep-waking pattern during dilatation. They consider the E.E.G. changes during the different stages of labour and assess the results against other techniques used to assess fœtal well-being. They record the effects on the E.E.G. of various anaesthetics and analgesics given to the mother. The difficulty of the technique is stressed and they conclude that despite the obvious interest of the technique it is not currently suitable for routine obstetric practice.
The failure of modern fetal monitoring techniques to measure either oxygenation or perfusion within the fetal brain may underlie their poor specificity in the detection of intrapartum hypoxia-ischaemia. We have adapted the technique of near-infrared spectroscopy (NIRS) to obtain continuous, quantified measurements of changes in human fetal cerebral oxygenation and blood volume during labour. More than 140 fetuses have been studied at University College London for periods ranging from 10 to 765 minutes. Reciprocal changes in the cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, indicating changing cerebral haemoglobin saturation, have been observed during uterine hyperstimulation with oxytocin, administration of maternal oxygen, changing maternal posture, and late fetal heart rate decelerations. Uterine contraction frequency greater than 1 every 2 minutes was associated with a fall in fetal cerebral oxygenation. A method for quantifying the oxygen saturation of hemoglobin derived from all vascular compartments (SmcO2) is described. There was a significant positive correlation between SmcO2 and umbilical artery pH. Conversely, the base deficit of blood from the umbilical artery showed a negative correlation with SmcO2.
Objective To test the hypothesis that late fetal heart rate decelerations are associated with a decrease in cerebral oxygenation.
Design Changes in fetal cerebral concentrations of oxyhaemoglobin and deoxyhaemoglobin were measured by near infrared spectroscopy, before, during and after contractions with late fetal heart rate decelerations and compared with changes during contractions with no alteration of heart rate.
Setting Teaching hospital obstetric unit.
Subjects Ten women in labour at term.
Results The changes in fetal cerebral oxyhaemoglobin and deoxyhaemoglobin concentrations that occurred during contractions were quantitatively similar, irrespective of the fetal heart rate changes. However, late fetal heart rate decelerations were associated with a significantly greater fall, after the uterine contraction, in the mean concentration of fetal cerebral oxyhaemoglobin of 0.52μmol/100g (SD 0.25) (P < 0.001) and a significantly greater rise in the mean concentration of deoxyhaemoglobin of 0.36 pmol/100 g (SD 0.35) (P < 0.01).
Conclusion Late fetal heart rate decelerations are associated with a significant decrease in cerebral oxygenation.
The uterine contraction patterns and the changes in fetal heart rate (FHR) were studied in cardio-tocographic recordings from 26 women in oxytocin-induced labour, 26 women in PGF2α-induced labour and 24 women during the later part of spontaneous labour. the contraction patterns and their effect on the FHR did not differ between the three groups. During the course of labour an increasing steepness of the upward slope of the contraction wave with increasing intensity of the contraction was found. High frequency of atypical contraction patterns, suggesting some degree of uterine incoordination was found during the active phase of labour in 10 patients, 8 of whom were primiparae. This incoordination could not be related to the effect of induction with either drug. Incoordinated contractions were associated with longer duration of labour and a tendency to more pronounced acidosis in the infant at birth, although mean values still fell in the normal range. Ominous FHR patterns were only seen in 2 cases of uterine hyperactivity during induction of labour.
All vaginal deliveries of the Department of Obstetrics and Gynecology of the University Basel (N=4081) during the year 74/73 and of the University Tübingen (N=3249) 75/74 were analysed using an IBM-system 370/135 Only alive singletons beyond the 28th week of gestation were analysed. Clinical management was quite different in the two departments; the incidence of vaginal operations (Basel 11.2%, Tübingen 12.6%), however, as well as the distribution of pH-values and Apgar-scores after 1 min were quite similar. Basel: Acidotic risk (i.e. pHUA<7.200) 13.5%, severe acidotic risk (i.e. pHUA<7.100) 1.55%, low Apgar-scores (1–3) 0.7%. Tübingen: 12.3%, 2.11%, 1.6%. 3.5% of all parturients (Basel) had duration of second stage of labour with active maternal pressure support lasting more than 30 min.
In two highly selected samples differing only with regard to the occurrence of cord-entanglements at birth (N1=1755, N2=1098) the association (rank correlation method according to Kendall) between the parameters of the fetal acid-base balance and the duration of second stage of labour as well as duration of the period with “active bearing down” was studied. Without cord encirclements pH in the umbilical artery fall −0.087 and in the umbilical vein −0.115 units and with cord complications the values amounted to −0.062 (UA) and −0.120 (UV) respectively pro 60 min duration of second stage with “bearing down efforts”. Analogous computations for pCO2, pO2 and HbO2 are presented. Apgar-scores in these samples showed a very loose connection with the time variables. From these data the conclusion is drawn that the indication to perform vaginal operations for termination of delivery should not primarily be governed by the factor time but rather by the whole obstetrical situation i.e. the possible fetal risk of the intervention. This holds only if maternal welfare is established and fetal well being is monitored continuously.
The well-documented limitations of our current methods of intrapartum surveillance have prompted research and development into a number of techniques with the potential to monitor the fetus during labour. Among these are near infra-red spectroscopy and pulse oximetry, both of which provide information regarding fetal oxygen status and utilise light in the near infra-red region of the spectrum.
All vaginal deliveries of the Department of Obstetrics and Gynecology of the University Basel (N = 4081) during the year 74/73 and of the University Tübingen (N = 3249) 75/74 were analysed using an IBM-system 370/135 Only alive singletons beyond the 28th week of gestation were analysed. Clinical management was quite different in the two departments; the incidence of vaginal operations (Basal 11.2%, Tübingen 12.6%), however, as well as the distribution of pH-values and Apgar-scores after 1 min were quite similar. Basel: Acidotic risk (i.e. pHUA less than 7.200) 13.5%, severe acidotic risk (i.e. pHUA less than 7.100) 1.55%, low Apgar-scores (1--3) 0.7%. Tübingen: :12.3%, 2.11%, 1.6%. 3.5% of all parturients (Basel) had duration of second stage of labour with active maternal pressure support lasting more than 30 min. In two highly selected samples differing only with regard to the occurrence of cord-entanglements at birth (N1 = 1755, N2 = 1098) the association (rank correlation method according to Kendall) between the parameters of the fetal acid-base balance and the duration of second stage of labour as well as duration of the period with "active bearing down" was studied. Without cord encirclements pH in the umbilical artery fall --0.087 and in the umbilical vein --0.115 units and with cord complications the values amounted to --0.062 (UA) and --0.120 (UV) respectively pro 60 min duration of second stage with "bearing down efforts". Analogous computations for pCO2, pO2 and HbO2 are presented. Apgar-scores in these samples showed a very loose connection with the time variables. From these data the conclusion is drawn that the indication to perform vaginal operations for termination of delivery should not primarily be governed by the factor time but rather by the whole obstetrical situation i.e. the possible fetal risk of the intervention. This holds only if maternal welfare is established and fetal well being is monitored continuously.
Data from 4081 vaginal deliveries (no caesarean sections) were analyzed retrospectively (IBM 730/158) with regard to duration of second and "final stage" of labour and fetal outcome (acid-base balance and apgar scores). The average duration of the two periods amounted to 22.8+/-29.6 and 9.9+/-7.8 min. Mean pH (UA) was 7.268+/-0.084 and the acidotic risk (pH less than 7.20, pH less than 7.10) 13.4 and 1.6% respectively. The distribution of the Apgar-scores after 1 min was assessed: 0-3: 1.7%, 4-6: 5.4%, 7-10: 92.9%. The dependance of the time variables from parity was studied. Two samples (N1=1755, N2=1098) of uncomplicated term pregnancies were chosen according to 7 clinical selection criteria differing only in the presence of cord entanglements at birth. The association between the two time variables and parameters of the fetal acid-base balance in cord blood was evaluated using rank correlation- and polynomial regression analysis. Highly significant correlations (tau) were found between the variable time and actual pH in blood of the umbilical artery and vein as well as pCO2, BEECF and HbO2 in the umbilical vein. The association however is not very close and thus clinically not of great importance. The deltapH (UA & UV) pro 60 min of second (and "final") stage of labour was computed and amounted to -0.024 (-0.087) in blood of the umbilical artery and -0.036 (-0.115) in blood of the umbilical vein and -0.017 (-0.062) (UA) and -0.032 (-0.120) units (UV) in the sample with and without apparent cord entanglements at birth respectively. The response of fetal acid-base balance to cord compression during second stage of labour was assesses: The acidotic risk (pH less 7.2) was doubled: 14.5% (7.7%) and AV-differences of all variables were "opened" if cordcoilings were observed. Apgar scores were not significantly different. Moreover, the association between AV-differences of each parameter and the variable time was studied: it became evident that with passage of time AV-difference is "closed" (-0.052 AV DpH/60 min "final stage" of labour, N=1098) indicating time related impairment of placental function. From these observations and data of the literature the conclusion is drawn that second stage of labour should not exceed 45 min in any patient. Furthermore it is concluded that in cases without signs of impending fetal distress it seems to be possible to wait more than 20 (Multipara) or 30 min (Primipara) duration of "final stage" without increased risk of fetal peril measured in terms of acidemia and clinical depression. This is valid only in term pregnancies with the possibility of continuous monitoring of FHR, in cases with normal uterine activity, uneventful course of first stage of labour and cooperative, vigorous patients. The indications for termination of delivery by vaginal operations in cases without impending fetal distress are discussed.
We investigated the effect of head compression and acidaemia during labour in 25 African primigravidae. Evidence that head compression had occurred during labour was confirmed by both clinical and radiological means at the end of a trial of labour. No significant difference could be demonstrated in the quantity of fetal electroencephalogram (EEG) abnormality that occurred in the groups with marked head compression as compared to the groups without marked head compression. Deterioration in the fetal EEG to a flat record known as electrocerebral silence (ECS) was associated with the development of acidaemia. As fetal heart rate (FHR) decelerations appeared the percentage of ECS in the fetal EEG record increased significantly (P less than 0.05), and likewise, as fetal acidaemia developed a highly significant increase in ECS in the fetal EEG was demonstrated (P less than 0.001). We concluded that in the management of trial of labour there was no significant deleterious change in the fetal EEG as a result of head compression, unless fetal acidaemia supervened. However, in the majority of these cases a significant increase in ECS to more than 20 per cent occurred in association with only moderate acidaemia (pH 7.25 to 7.30).
A total of 1,503 vaginal deliveries with the Shute parallel forceps during a 10 year period are analyzed as to the risk of instrumental damage. In this series, 35 infants died intrapartum or neonatally. Eliminating all deaths from unrelated causes, three remain in which the forceps could possibly have been implicated. Investigation of these, however, revealed in each case the presence of other concomitant and potentially lethal factors, none of which could be completely ruled out as the primary cause of fetal death. Each of the three cases is discussed in detail. We conclude from our series that the Shute forceps is useful in the delivery of premature infants, but should be employed for this maneuver only by very experienced operators. In these cases, midforceps should be performed only for critical indications. The risk of damage with parallel forceps deliveries from the pelvic floor is minimal if decision for operation is based on cardiotocographic criteria, and under favorable degrees of oxygenation. In the delivery of the immature infants, the parallel forceps can, in fact, hardly be superseded by any other instrument because of its unique controlled protection of the fragile fetal head from even the pressures of the birth canal. Delivery with the Shute forceps can be performed effectively under pudendal block or local infiltration anesthesia.
This study reports the effects of spontaneous rupture of membranes and artificial rupture of membranes on fetal heart rate patterns during labour in 87 normal and 25 complicated pregnancies. The incidence of early deceleration patterns following membrane rupture was 6.25 per cent during the first 15 minutes and 1.78 per cent after 45 minutes, regardless of whether the pregnancy was normal or complicated. It is concluded that rupture of membranes does not significantly increase the incidence of early deceleration patterns. However, the occurrence of other heart rate alterations such as late decelerations, loss of beat-to-beat variability, changes in base line and tachycardia, need to be investigated further in larger collaborative studies.
Intraamniotic pressure was studied in the 30th week of amenorrhea in relationship with fetal intracranial pressure with open-tip catheters. The fetus had a severe hydrocephalus (echoscopy 16 cm) due to a teratologic malformation of the cerebrum. Clinically nonoperative treatment was indicated. Intracranial pressure (X) was invariably higher than intraamniotic pressure (Y) between contractions: Y = 2.04 + 0.54 X, and during contractions: Y = 5.30 + 0.55 X. There was no definite relationship between intrauterine and intracranial pressure, and the fetal tachogram. A definite relationship was established with the supine position of the patient and decelerations in the fetal tachogram. It is suggested that when fetal cardiac decelerations are seen during the first stage of labor it seems advisable to look for factors such as umbilical cord compression and decrease of materno-placental perfusion rather than fetal head compression.
In the past twenty years, the vacuum extractor has gained wide use in Europe with an associated decrease in perinatal mortality. There, its use is considered by many to be much safet than a forceps delivery. Certain complications are associated with its use, but in general these are minor and transitory. On analysis, most of the serious complications reported in the literature are considered to be due to other associated factors, or to misuse of the vacuum extractor. Experience with the vacuum extractor in the United States has been minimal, and most authors feel that there are few indications for its use. Perhaps it is time that obstetricians in the United States take a more careful look at the European experience, and give the vacuum extractor a fair trial.
Intra-uterine pressure (IUP), intracranial pressure (ICP) and fetal heart rate (FHR) were simultaneously recorded during labor in a severely hydrocephalic fetus. After cephalocentesis, 600 ml of liquor cerebrospinalis was drained. ICP exceeded IUP, but the increase in ICP was less than the increase in IUP during most of the contractions. The FHR showed marked decelerations during uterine contractions and changed gradually into a persistent bradycardia. The pathophysiology of fetal heart rate patterns during labor is discussed and the literature has been reviewed.
The purpose of this study was to measure by near-infrared spectroscopy changes in human fetal cerebral oxyhemoglobin, deoxyhemoglobin, and cerebral blood volume during labor and to calculate mean cerebral hemoglobin oxygen saturation.
The effects of uterine contractions with and without fetal heart rate decelerations were compared in eight singleton term fetuses. Results were analyzed by analysis of variance.
In six of eight fetuses normal uterine contractions were associated with proportional decreases in both oxyhemoglobin and deoxyhemoglobin and a fall in cerebral blood volume without desaturation of cerebral hemoglobin. Contractions with fetal heart rate decelerations produced different results in that oxyhemoglobin fell but deoxyhemoglobin rose, indicating cerebral desaturation. In two of the eight fetuses normal contractions were associated with increases in oxyhemoglobin, deoxyhemoglobin, and cerebral blood volume; no decelerations were seen in either fetus. Mean cerebral hemoglobin oxygen saturation calculated during normal contractions was 43% +/- 10% (SD).
Uterine contractions were associated with detectable changes from baseline in cerebral oxyhemoglobin, deoxyhemoglobin, and cerebral blood volume.
The purpose of this study was to determine the cause and physiologic consequences of variable decelerations.
Previous studies of heart rate changes in human and experimental animals were critically reviewed with respect to the autonomic nervous system component, the cause of the increased vagal activity, and the role of cord compression or other stimuli in these heart rate changes.
There is abundant evidence from experimental and human studies that variable decelerations can be reproduced by either cord compression or head compression. The vagal reflex produced is probably caused by a combination of chemoreflex (earlier in the deceleration) and baroreflex (later). The variable deceleration is accompanied by an acidosis, primarily respiratory, and probably hypoxemia. Cord compression results in decreased umbilical blood flow.
Recent Doppler velocimetry studies suggest that even though the variable decelerations may be similar in duration and depth, the reduction of umbilical blood flow may be greater when the prime cause is cord compression than when the prime cause is vagal reflex from another source.
Fetal head compression during normal labor can increase intracranial pressure (ICP). We studied the cerebral and peripheral blood flow responses to ICP elevation in utero in chronically catheterized fetal sheep using the radiolabeled microsphere technique. ICP was elevated, stepwise, in increments of 6 +/- 1 mm Hg by infusion of artificial cerebrospinal fluid into a lateral ventricle. When ICP was raised to within 28 mm Hg of baseline mean arterial blood pressure (i.e., ICP above 22 mm Hg), arterial pressure began to increase. Above this ICP level, up to 41 mm Hg, mean cerebral perfusion pressure was maintained by equivalent increases in arterial pressure. Cerebral blood flow and O2 uptake at the highest ICP levels were not different from baseline values. Changes in peripheral organ blood flow were graded according to the level of ICP. At the highest level (ICP = 41 mm Hg), renal, gastrointestinal, and skin blood flow decreased by 68%, 69%, and 65%, respectively. Myocardial and adrenal blood flow doubled, whereas heart rate and cardiac output were unchanged. Placental blood flow increased in proportion to arterial pressure. Arterial plasma epinephrine, norepinephrine and arginine vasopressin increased by nearly two orders of magnitude. Therefore, as ICP approaches baseline mean arterial pressure, fetal lambs are capable of sustaining cerebral perfusion by initiating profound visceral vasoconstriction without curtailing placental blood flow. Since cerebral O2 uptake was maintained, there is no evidence that stimulation of the peripheral response requires pronounced cerebral ischemia. This highly developed Cushing response may be important for ensuring cerebral viability when the fetal head is compressed during parturition.
Sometimes the relationship between peripartum events and neonatal CNS injury is obvious: for example, following complete abruptio placentae or umbilical cord prolapse and occlusion with a delay of many minutes before delivery of the baby. These circumstances are, of course, rare in modern obstetrics. Usually, when a neonate develops neurological injury, a host of various potentially adverse peripartum factors are assumed to be the aetiology, but without definitive evidence. Among these latter factors are those we have focused on in this paper: the mechanical forces exerted on the fetal head during labour when the full-term fetus is in cephalic presentation.
Fetal head compression pressure (FHCP) and its clinical importance has been investigated in a group of 46 spontaneous births. Measurement of FHCP was facilitated using a compression transducer positioned between the fetal head and the wall of the birth canal. This method not only constitutes a means of quantitating the forces acting directly on the fetal head, but also provides information about the intracranial pressure generated during delivery. The latter extrapolation is based on the principle of applanation. The technique provides an objective and reliable estimate of intracranial strain and therefore a means of comparing the forces generated under different delivery modes. The condition of the same neonates at birth was assessed using umbilical artery pH, Apgar score, neurobehavioral testing and fundoscopic examination. The mean amplitude of FHCP in the different deliveries ranged from 38 to 390 mmHg (5-52 kPa) with an overall mean of 157.9 mmHg (21.1 kPa). The study indicated that the appearance of retinal hemorrhages in the newborn cannot be explained by exposure of the fetal head to abnormally high compression during birth. Other explanations must be sought for infants with a neurobehavioral deficit, reduced Apgar score, or umbilical artery acidosis at birth. It is concluded that a relatively short period of high FHCP has no obvious consequences for fetal well-being, at least within the limits described in the present report.
Two hundred twenty newborn infants with one or more fetal or newborn complications and 54 newborn infants without fetal or newborn complications were prospectively studied to assess the relationship between maternal, obstetric, fetal, and newborn complications and intracranial hemorrhage. Intracranial hemorrhage occurred in 47 newborn infants with fetal or newborn complications (21%) and in one infant with no fetal or newborn complications (2%). Maternal and obstetric complications, duration of labor, and mode of delivery were not associated with intracranial hemorrhage. Newborn immaturity at delivery is an important factor in the occurrence of intracranial hemorrhage. There is little evidence that fetal hypoxia is a contributing factor. Severe respiratory complications and major infections are newborn complications associated with intracranial hemorrhage.
Fetal heart rate variations and uterine contractility were studied by continuous monitoring in 17 spontaneous labors and 17 elective inductions. The pregnancies were at term and without known complications. The incidence of type I dips was lower in spontaneous labors than in elective inductions (21 and 49 per cent, respectively, p < 0.001). The intensity of contractions was lower in spontaneous labors (
= 38 mm. Hg) than in elective inductions (
= 43 mm. Hg) (p < 0.001). In both groups the intensity of contractions and the incidence of type I dips were directly related. At a given intensity the incidence of type I dips was greater in the induced labors. The higher incidence of type I dips found in the induction group could be attributed to the greater intensity of contractions and the counter pressure on the fetal head caused by a greater resistance of the birth canal. Type I dips are caused by uneven compression and deformation of the fetal head which may cause EEG alterations, cerebral lesions, and neurological sequelae. We recommend the proscription of inductions when no important medical indications justify them.
A new vacuum electrode for fetal electroencephalography is described, and preliminary results of its application are presented.
Fetal heart rate patterns, including instantaneous heart rate and intrauterine pressure, were recorded in 3 hydrocephalic fetuses during labor. Intracranial pressures were also monitored in two of these fetuses. Intracranial pressure invariably exceeded intrauterine pressure. No consistent heart rate patterns were seen in these anomalous fetuses.
A single dose of 0.5 mg prostaglandin E2 in viscous gel was administered intracervically to induce labor in 150 patients with a favorable cervix. All but 5 patients (97 per cent) were delivered within 12 hours. No adverse maternal or fetal effects were registered. The method, which enables induction without primary amniotomy, was easy to perform and well accepted by the patients.
In a population of high-risk patients who had continuous "direct" monitoring during labor, 598 (46%) had no decelerations during the first stage, while 247 (19%) had presented early decelerations before completion of dilatation. The clinical characteristics, the fetal heart rate (FHR) baseline alterations, and neonatal outcome were compared between these two groups: there were no differences in any of the aspects evaluated, except that there was transient tachycardia more often among the early-decelerations group. The patients who had no decelerations were subdivided into vaginal deliveries and cesarean deliveries, and the same parameters were compared again: the cesarean section group had longer recordings and more contractions, lower Apgar 1 and 5 minute scores, and higher incidences of Apgar scores less than or equal to 6 at 1 minute, while all other aspects were similar. A possible explanation was that 82% of cesarean sections were done under general anesthesia and only 3% of vaginal deliveries. The implication of ruptured membranes in the etiology of early decelerations was extensively reviewed and discussed in view of these findings. It is concluded that amniotomy does not seem a maneuver deleterious to the fetal well-being.
To determine the relationship between contraction related changes in fetal heart rate and cerebral oxygenation measured by near-infrared spectroscopy during labour.
A specially designed optical probe was inserted through the dilated cervix and placed against the fetal head in 30 women during labour. Alterations in fetal heart rate during the final hour of the first stage of labour were compared with changes in the cerebral haemoglobin oxygenation index (delta oxyhaemoglobin concentration - delta deoxyhaemoglobin concentration) measured before, during and after uterine contractions.
Uterine contractions which were associated with either no alteration, accelerations or early decelerations of the fetal heart rate showed no significant changes in the haemoglobin oxygenation index. Variable, late and prolonged decelerations all showed significant decreases in the haemoglobin oxygenation index (P < 0.01) either during (variable) or after (variable, late and prolonged) the uterine contraction.
The association between variable, late and prolonged FHR decelerations and significant falls in cerebral oxygenation during late labour suggests that these fetal heart rate patterns are associated with an increased risk of fetal cerebral hypoxia.
NIRS as a technique for intrapartum fetal monitoring is at present only able to be used as an investigative research tool. We feel that it has enormous potential to give access to previously inaccessible information about fetal cerebral haemodynamic and oxygenation changes in labour. The major limitations at present are technological, and the problems addressed in this review need to be resolved before clinicians can advance the technique. In the future, standardized measurement parameters that truly reflect cerebral oxygenation, along with a range of normality need to be established. This would require the study of very large numbers of uncomplicated labours. Comparison with data from labours complicated by what we currently call 'fetal distress' and correlation with outcome measures in the neonate would then be needed to determine abnormal patterns of change related to intracerebral hypoxia-ischaemia. This is severely limited by the current inability to measure absolute levels of oxygenation necessary to validate the method. To use the technique for routine surveillance in labour would require considerable refinement of both the equipment and the data analysis systems to improve the acceptability of the technique. It is not possible to envisage a role for NIRS in routine surveillance of low-risk pregnancies, but it may in future prove to have a role in the management of high-risk pregnancies and may well improve our understanding of intracerebral pathology.
Fetal head compression during labor may increase intracranial pressure (ICP) and decrease cerebral perfusion pressure (CPP). An increase in mean arterial pressure (MAP) associated with the Cushing response normally acts to mitigate an ischemic insult when the increase in ICP approaches MAP. However, the premature fetus may be limited in its ability to increase MAP. We compared the efficacy of the pressor response in sustaining CPP, cerebral blood flow (CBF), and cerebral O2 consumption (CMRO2) in chronically catheterized fetal sheep at 0.6 gestation (92 d; n = 7) and 0.9 gestation (133 d; n = 7). When fetal ICP was increased to baseline MAP (41 +/- 3 mm Hg; +/-SEM) in 92-d fetuses, MAP increased by 7 +/- 2 mm Hg and remained stable during 30 min of constant ICP elevation; CBF decreased by 72% and CMRO2 decreased by 46%. In 133-d fetuses, MAP increased from 53 +/- 2 to 65 +/- 4 mm Hg at 3 min of elevated ICP; CBF decreased by 62% and CMRO2 decreased 30%. However, MAP continued to increase after 3 min and reached a stable level of 75 +/- 3 mmHg at 30 min in 133-d fetuses. The additional increase in MAP restored CBF and CMRO2 to baseline values. Plasma epinephrine and vasopressin concentrations increased between 6 and 33 min of elevated ICP to levels, exceeding those in 92-d fetuses. We conclude that the arterial pressure response to intracranial hypertension is present at 0.6 gestation but is less well developed than at 0.9 gestation in fetal sheep, possibly due to immaturity of the sympathoadrenal and vasopressin systems. Consequently, CBF and CMRO2 are not as well defended at mid-gestation against elevated ICP as might occur during difficult labor.
The inaccuracies of the modern obstetrical forceps and their possible relationships to perinatal mortality are outlined and discussed. A metric forceps designed by one of us, capable of measuring and recording the forces of compression and traction exerted during delivery, is presented. This modification is adaptable to almost any obstetrical forceps. The tracing obtained with this forceps has been referred to as an electrodelivery graph which has been abbreviated to EDG. No conclusions have been drawn. It is felt that many enlightening experiments and studies could result from the use of this instrument. It is feasible that after several thousand deliveries and proper following of the infants delivered with this instrument that a new forceps could be designed which would be incapable of exerting dangerous forces.
Thesis (M.M.S.)--Ohio State University, 1964.
• 1.1. Fetal heart rate changes were monitored in 62 births in which delivery was accomplished by the vacuum extractor and/or Simpson forceps.
• 2.2. The intensity of each pull in these instrument deliveries was measured in pounds by both mechanical and electronic systems.
• 3.3. Fetal bradycardia which developed during the process of applying the forceps to the fetal head was associated with a high incidence of neonatal asphyxia.
• 4.4. Slowing of the fetal heart rate during traction was a very common occurrence during both vacuum extractor and forceps deliveries.
• 5.5. Forceps deliveries in which individual pulls of 50 or more pounds were required were associated with a high rate of depressed infants at birth.