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Cohain, JS. Nuchal Cords are Necklaces, not Nooses.
Midwifery Today. 2010. 93:
http://monoamnioticstories.blogspot.fr/
Cords of monoamniotic twins alive and well
The Percent of nuchal cords increases with gestational age:
24-30 weeks = 12 %
30-32 weeks = 16%
32-38 weeks = 26%
38- delivery = 35%
Nuchal Cords are Necklaces, not Nooses
By Judy Slome Cohain, CNM
Abstract: Research based on 182,492 births, wielding statistical power to uncover even mild
negative associations, showed that both single and multiple nuchal cords at the time of delivery
are not associated with adverse perinatal outcomes. Nuchal cords are associated with higher
birth weights and lower cesarean section rates than births without nuchal cords. Color Doppler
ultrasound, intended specifically to diagnose nuchal cords hours before delivery, has diagnosed
the presence of 35-80 percent of the nuchal cords found on delivery, and has a false positive rate
of 19 percent. The rate of nuchal cords increases with increasing gestational weeks. Present
technology cannot reliably predict the presence of a nuchal cord, tell whether a nuchal cord is
tight, or determine anything regarding the likelihood of hypoxia, IUGR or stillbirth. Intervention for
the supposed presence of single or multiple loops of nuchal cord or a true knot, suspected by
ultrasound prenatally, is unjustified because diagnosis by ultrasound is unreliable and intervention
involves greater risk to the baby than the nuchal cord. Since nuchal cords occur at rates of 30 to
34 percent at 40 weeks and are not associated with adverse perinatal outcomes, practitioners
and women should consider their presence reassuring and normal. Given the common
occurrence of nuchal cords and its very high association with a favorable outcome, scanning for
nuchal cords appears to have no efficacy. Efforts to define and diagnose new antepartum
“problems” continue to outstrip our ability to improve outcomes by diagnosing and/or “treating”
newly defined problems.
Ultrasound diagnosis of a cord around the neck was first described in 1982.(1) Before
that, in 1980, the most up-to-date, respected obstetric textbook included only one single
sentence in the entire textbook regarding cords around the neck: “Coils occur in about 25
percent of cases and ordinarily do no harm, but occasionally they may be so tight that
constriction of the umbilical vessels and consequent hypoxia result.”(2)
The name “nuchal cord” and “cord entanglement” for a cord around the neck has grown
popular in the last 20 years, around the same time ultrasound achieved the ability to
detect, albeit unreliably, a nuchal cord.
No study has ever demonstrated 100 percent accuracy at identifying nuchal cords. Since
nuchal cords come and go during pregnancy, there is no way to know the accuracy of
prenatal ultrasound without immediately opening the abdomen surgically to check for a
cord. There is some research, however, that looks at nuchal cords within hours of actual
delivery. One study, conducted in 2004, specifically tested the accuracy of ultrasound in
diagnosing a nuchal cord. It was performed hours before delivery.(3) Each of the 289
women tested underwent a transabdominal ultrasound scan with an Aloka 1700
ultrasound machine with a 3.5 MHz abdominal probe, using gray-scale and color Doppler
imaging, immediately prior to induction of labor. Presence of the cord was sought in the
transverse and sagittal plane of the neck. A nuchal cord was diagnosed if the cord was
visualized lying around at least three of the four sides of the neck. A cord was actually
present in 52 of the 289 women at delivery. Only 18 of the 52 cords (35%) were detected
on color Doppler ultrasound imaging done immediately before delivery, and 65 % of
nuchal cords were not detected. Of the 237 babies born with no nuchal cord at delivery,
ultrasound claimed there was a nuchal cord in 44 (19%) of those cases. In this study,
ultrasound was only 35 percent accurate at finding a single-loop nuchal cord and only 60
percent accurate at detecting a nuchal cord wrapped multiple times around the neck. In
another study, there was a 6% false positive rate 4% false negative rate of cords (12)
Three-dimensional sonography identified in utero 73.3% single and 60% multiple nuchal cords
found at birth.(13).
Since nuchal cords come and go, without abdominal surgery, there is no way to confirm
or disprove the accuracy or lack of accuracy of ultrasound diagnoses of studies done
before labor.
In no study was it possible for ultrasound imaging to distinguish between a loose or tight
cord on ultrasound, although this has been attempted in at least three studies. Peregrine
concludes that ultrasound diagnosis of nuchal cords will only be useful if we are able to
diagnose them reliably as well as predict which of those fetuses are likely to have a
problem.(3) Since neither of those capabilities exists, looking for a nuchal cord on
ultrasound is useless. Ultrasound measurement of the velocity of flow in the cord may be
useful in the management of twins and chronically growth-restricted fetuses.
Clapp attempted to find out the rate at which nuchal cords come and go during
pregnancy.(4) He recruited 84 healthy, nonsmoking, nonsubstance-abusing women
carrying a single fetus, with dates confirmed by 8- to 10-week ultrasounds, before the
20th week of gestation. The women all agreed to four extensive ultrasounds at 24-26, 30-
32 and 36-38 weeks gestation and during labor and delivery, evaluating fetal biometry,
fetal tone and fetal motion. The ultrasound tests used color flow Doppler imagining to
determine whether a nuchal cord was present and also monitored breathing movements,
amniotic fluid volume, fetal flow redistribution, and velocity flow profiles from the
umbilical artery at the body wall and placental insertion as well as at the origin of the
fetal middle cerebral artery. Clapp reports that in 60% of women, a nuchal cord was seen
on ultrasound at one of the four evaluations, yet at full term at mosyt 35% are born with a
nuchal cord. The data suggested that the likelihood of a nuchal cord linearly increases as
the pregnancy advances.
Larson had similar findings.(5) He found of the 13,895 singleton deliveries he analyzed,
a nuchal cord appeared in 6 percent at 20 weeks to 29 percent at 42 weeks gestation. It
appears that the rate of nuchal cords increases with gestation.
Clapp was the first to blind his physicians to the presence or absence of a nuchal cord on
ultrasound when they did clinical evaluations for assessing fetal well-being. Their
clinical evaluations found no difference between fetuses thought to have a nuchal cord
and those without. Clapp points out that in all research showing a difference in the well-
being of fetuses with a nuchal cord, the physician was not blinded to the supposed
presence or absence of a nuchal cord.
Considering the well-accepted myth of the danger of nuchal cords, the most surprising
outcome of recent research is that nuchal cords are not associated with adverse perinatal
outcomes. This was the conclusion of every study since 2000. The largest studies were
published in 2005 and 2006. The first study examined 4,426 term deliveries (37-42
weeks) retrospectively, finding 17.5 percent born with a nuchal cord.(6) There was no
significant difference in birth weight, nonreassuring fetal heart rate pattern, need for
operative delivery, 5-minute Apgar <7, or admission to the NICU nursery, even in the
group with two or more loops around the neck. The babies without nuchal cords had
significantly higher rate of cesarean delivery. The next study, which was published in
July 2005, looked at 11,748 term (37 weeks or longer) deliveries.(7) Researchers found a
rate of 34% nuchal cords in the group that delivered between 37-41 weeks, and 35
percent had nuchal cords in the group that delivered after 41 weeks. The babies born with
nuchal cords had more 1-minute Apgar scores <7, but had no difference in 5-minute
Apgar scores and no increase in NICU admissions. In the third study (8) (the largest
study of nuchal cords published) 166,318 deliveries were examined retrospectively.
Sheiner, et al., found 14.7% with a nuchal cord at delivery including all deliveries at any
week of gestation. Although previous studies have found babies with nuchal cords to
weigh 50 grams less than those without, this study found babies with a nuchal cord to
weigh 50 grams more on average than those without. Sheiner again found the 1-minute
Apgar scores to be significantly lower in the group with a cord, but the 5-minute Apgar
scores to be the same. Perinatal mortality rate was significantly lower in pregnancies with
a nuchal cord compared to those who delivered without a nuchal cord. Altogether these
studies represent the outcomes of 182,492 births, which all showed less morbidity and
less mortality associated with having a nuchal cord. Nuchal cords are associated with
nonreassuring fetal heart rate patterns, probably leading to higher rates of lower Apgar
scores at 1 minute, but not at 5 minutes. In addition to the large studies, two smaller
studies performed since 2006 have confirmed these results, one of 202 nuchal cords(10)
and one of 512 nuchal cords(11). Both found Apgar scores <7 at 1 minute significantly
higher in the nuchal cord group, but Apgar scores at 5 minutes were the same in both
groups; admission to the neonatal unit was not more common; and nuchal cord was not
associated with adverse perinatal outcome.
Rare cases of cords wrapped multiple times around the body, limbs and neck, with or
without a true knot, have been said to be associated with, but never proved to have caused
stillbirth.(4) The studies that have published an increase in the risk of stillbirth with
nuchal cord did not control for risk factors such as hypertension, abruption, diabetes,
premature rupture of the membranes, oligohydramnios or major fetal anomalies --
meaning that the stillbirth may have had nothing to do with the position or knot of the
cord.(3)
True knots in the umbilical cord occur in just over 1 percent and are said to be associated
with an increase in stillbirth in retrospective case studies.
“The appropriate treatment of patients for whom a true knot was supposedly
identified with ultrasonography during the antepartum period is unclear. It is
possible and even probable that antepartum biophysical testing will not prevent
fetal death, given the unpredictability and suddenness of cord occlusion in these
patients. This dilemma is complicated by the unknown accuracy of the diagnosis,
which undoubtedly varies considerably with gestational age. Even if
ultrasonography was highly sensitive and specific for the diagnosis of a true knot
in the umbilical cord, it is likely that, given the low prevalence of this condition,
the predictive value of the diagnosis would be disappointingly low. For example,
with a prevalence/occurrence rate of 1 percent, a sensitivity of 90 percent, and a
specificity of 95 percent, the positive predictive value of the diagnosis of a true
knot would be only approximately 15 percent. Even with an unrealistically high
degree of accuracy, such as a sensitivity of 100 percent and a specificity of 99
percent, only 1/2 of the patients who are diagnosed with a true knot in the cord
would actually have one. Obstetricians might cause considerable mischief by
aggressively treating these patients, given the poor predictive value of the
diagnosis and the unknown outcome efficacy of such treatment.”(9)
In my own homebirth practice, the most frequently asked question by new clients is
whether it is safe to have a homebirth because “What if the cord is around the baby’s
neck?” At least 50 percent of new clients ask that question and the other 50 percent may
be silently thinking it. It is amazing how successfully the medical myth of the danger of a
nuchal cord has been so effectively propagated in the past 27 years. Perhaps people
associate a cord around the neck with being strangled. A fetus is not being strangled by a
cord because the baby is not hanging by it from a tree, but rather happily swimming in a
balloon of sterile amniotic fluid. If a cord gets compressed during delivery, this may be
reflected in his/her 1-minute Apgar, but a minute later, the cord is working well again,
reflected in his/her 5-minute Apgar.
Given the common occurrence of nuchal cords and its very high association with a
favorable outcome, scanning for nuchal cords appears to have no efficacy.
1. Jouppila, I P., and P. Kirkinen. 1982. Ultrasonic diagnosis of nuchal encirclement by
the umbilical cord: a case report. J Clin Ultrasound 10(2): 59-62.
2. Pritchard, J., A. Jack, J. Williams and P. MacDonald. 1980. Williams Obstetrics, 16th
edition. Norwalk, Connecticut: Appleton-Century-Crofts, 421.
3. Peregrine, E., P. O’Brien and E. Jauniaux. 2005 Ultrasound detection of nuchal cord
prior to labor induction and the risk of Cesarean section. Ultrasound Obstet Gynecol
25(2): 160-64.
4. Clapp, JF, 3rd , et al. 2003. Natural history of antenatal nuchal cords. Am J Obstet
Gynecol 189(2): 488-93.
5. Larson, JD , WF Rayburn and VL Harlan. 1997. Nuchal cord entanglements and
gestational age. Am J Perinatol14(9): 555-57.
6. Mastrobattista, JM , etal. 2005. Effects of nuchal cord on birth weight and immediate
neonatal outcomes. Am J Perinatol 22(2): 83-85.
7. Schäffer, L., et al. 2005. Nuchal cords in term and postterm deliveries - - Do we need
to know? Obstet Gynecol 106(1): 23-28.
8. Sheiner, E ., et al. 2006. Nuchal cord is not associated with adverse perinatal outcome.
Arch Gynecol Obstet 274(2): 81-83.
9. Stempel, LE. 2006. Beyond the pretty pictures: Giving obstetricians just enough
(umbilical) cord to hang themselves. Am J Obstet Gynecol 195(4): 888-90.
10. Ghosh, GS and S. Gudmundsson. 2008. Nuchal cord in post-term
pregnancy-relationship to suspected intrapartum fetal distress indicating operative
intervention. J Perinat Med 36(2): 142-44.
11. Shrestha NS , Singh N. 2007. Nuchal cord and perinatal outcome. Kathmandu Univ
Med 5(3):360-3.
12. Bolten K, Chen FC, Salomon N, Dudenhausen J. Antenatal diagnosis of nuchal cord.
Ultrasound in Obstetrics & Gynecology 2009; 34 (Suppl. 1): 146.
Methods: During a one-year period pregnant women who intended to undergo vaginal delivery were examined by two specialists in
Materno-Fetal Medicine at the time of admission to the delivery room. Doppler-ultrasound was used to check for the presence of
nuchal cords. Subsequently, the incidence of nuchal cords at delivery was recorded so as to obtain the specificity and sensitivity of
antenatal sonography in examining nuchal cords, as well as positive predictive (PPV) and negative predictive values (NPV).
Results: Of 263 pregnant women examined, nuchal cords were detected with Doppler-ultrasound in 91 (34.6%). At birth 86
(32.7%) of the newborns had a nuchal cord. A false positive diagnosis occurred in 15, a false negative diagnosis in 10 cases.
13.Hanaoka, T. Yanagihara, A. Kuno, H. Tanaka & T. Hata. 2001. A critical evaluation of three-dimensional and two-
dimensional sonographic studies, and color Doppler ultrasound in detecting nuchal cord in utero.
Ultrasound in Obstetrics & Gynecology.18: 0: P81
Methods: Eighty-five singleton pregnancies without nuchal cord and 35 with nuchal cord (30 single nuchal cord, four double nuchal
cords, and one triple nuchal cords) were studied within 1 week before delivery using a transabdominal three-dimensional sonography.
Two-dimensional sonography and color Doppler ultrasound were also conducted.
Results: Three-dimensional sonography identified in utero 22 (73.3%) single and 3 (60%) multiple nuchal cords found at birth. There
were no significant differences in overall diagnostic indices of each diagnostic modality for detecting nuchal cord. However, the
ability to view nuchal cord was better with three-dimensional sonography than with two-dimensional sonography or color Doppler
ultrasound. Conclusions: Three-dimensional surface imaging does not provide more useful diagnostic information than two-
dimensional sonography and color Doppler ultrasound for detecting nuchal cord in utero.
Bio: “I would have died if I was born at home because the cord was around my neck!”
and “We saved your baby’s life because the cord was around the neck!” are oft repeated
phrases in our worlds. Nuchal cords are valuable necklaces. Lets see how quickly we can
dismiss the 20 year old nuchal mythology and propagate the truth about nuchal cords.
