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Diagnosis of Labor: a Prospective Study
Antonio Ragusa, MD; Mona Mansur, MD; Alberto Zanini, MD; Massimo Musicco, MD, PhD;
Lilia Maccario, MD; Giovanni Borsellino, MD
Medscape General Medicine. 2005;7(3) ©2005 Medscape
Abstract and Introduction
Accurate diagnosis of the onset of labor remains a problem in obstetrics. Criteria commonly used to
diagnose labor have never been scientifically evaluated. This prospective study involved 423
pregnant women who presented themselves with uterine contractions to 2 Italian hospitals (248
nulliparous patients total and 175 multiparous total) and who were either admitted or advised to
return home. The obstetrician on duty collected data using a standardized form that listed common
criteria for labor diagnosis. Multivariate analysis showed that a reduction of the interval between
consecutive uterine contractions, odds ratio [OR] = 1.42; 95% confidence interval [95%CI] 1.06-
1.90); abdominal pain of increasing intensity (OR = 1.42; 95% CI 1.01-2.02); cervical effacement
(OR = 1.4; 95%CI 1.12-1.77); and cervical dilation (OR = 1.91; 95% CI 1.53-2.38) were significant
markers of the onset of labor. On the other hand, backache had a negative diagnostic value (OR =
0.78; 95% CI 0.61-0.99). The value of criteria such as regular uterine contractions, loss of mucous
plug, changes in intestinal habits, vomiting, pain that is relieved by walking, and changes in
breathing pattern did not reach statistical significance.
A considerable amount of research has focused on cesarean delivery prevention. Yet, no strict
definition of labor has been proposed, and accurate diagnosis of labor remains a problem in
obstetrics. Criteria commonly used to diagnose labor have never been scientifically evaluated. The
principal aim of this study was to evaluate criteria that might lead to a practical method of
determining the time of onset of labor.
The interval between contractions diminishes gradually from approximately 10 minutes in early
labor to as little as 2 minutes near the end of labor. In the normal process, there is a progressive
increment in the strength of contractions from the onset of labor to late moments of labor. The
definition, or clinical diagnosis, of labor is a retrospective one. There is no laboratory test that yields
a "labor titer" or another procedure that can define the difference between the laboring and
nonlaboring patient. Given these limitations, the patient is diagnosed as being in labor when a
combination of conditions exists.
An incomplete understanding of labor may lead to unnecessarily early intervention. In case of
slower than expected progress in the first stage of labor, for example, the obstetrician may decide to
proceed with augmentation (stimulation of inadequate uterine contractions); but commencing
treatment too early can cause undesired induction with oxytocin or amniotomy. If treatment
commences too late, on the other hand, there is a danger that the uterus will become exhausted,
leading to reduced uterine activity and dystocia, and it may not then respond to the therapy.
Accurate diagnosis of labor would have the benefit of allowing the obstetrician the opportunity to be
specific in his or her choice and timing of treatment.
Materials and Methods
The intention of this prospective study was to study patients who may well be in labor. Four hundred
twenty-three pregnant women with uterine contractions were seen consecutively at the obstetric
wards of the Saronno and Monza hospitals, which are National Health Service (NHS) hospitals
located in Lombardia, in the north of Italy.
During their examination, the obstetrician on duty collected data using a standardized form that
listed criteria commonly used to diagnose onset of labor, including criteria other than that obtained
from a physical examination ( Table 1 and Table 2 ).
All of the criteria in Table 1 and Table 2 have been noted in published literature as markers of labor.
If a patient was judged to be in labor by the obstetrician on duty, that patient was admitted to the
labor ward after the physician had completed the standardized form; if a patient was not judged to be
in labor, the physician discharged the patient after completing the form. Finally, a retrospective
evaluation of the real onset of labor was documented by the study's coordinator (Dr. Ragusa).
The study was approved by the local institutional review board for clinical investigations and met all
criteria put forth by the Declaration of Helsinki. All participants provided written informed consent
before participation in the study. A data safety and monitoring board provided data and safety
Statistical multivariate analysis indicates that of the criteria that do not require a physical
examination, only the reduction of interval between uterine contractions (OR = 1.42; 95% CI 1.06-
1.90) and abdominal pain of increasing intensity (OR = 1.42; 95% CI 1.01-2.02) were positively
associated with labor and reached statistical significance (P = .038 and .042, respectively). Of
criteria that do require a physical examination, only cervical effacement (OR = 1.4; 95% CI 1.12-
1.77) and cervical dilatation (OR = 1.91; 95% CI 1.53-2.38) were positively associated with labor
and reached statistical significance (P = .023 and .018). On the contrary, backache was inversely
correlated to the diagnosis of labor (OR = 0.78; 95% CI 0.61-0.99; P = .047) ( Table 3 , Table 4 ,
Table 5 , Table 6 ).
We aimed to determine the necessary criteria needed to find a real and practical definition of the
moment of the onset of labor. We cannot rely on our patients' determinations, as women's
recognition of the spontaneous onset of labor may be incorrect. An incorrect diagnosis (10% of
cases) may lead to poor management of labor and, as a consequence, unnecessary induction or
prolonged labor. Moreover, a proper diagnosis will surely reduce the number of unnecessary
cesarean deliveries and the instrumental delivery rate[5,6] through early detection and correction of
dystocia. Later hospital admission (at ≥ 4 cm cervical dilation) and management of perinatal care by
qualified midwives in collaboration with obstetricians has been shown to increase the rate of
spontaneous vaginal delivery in low-risk women. But a policy of later admission demands
precision in the diagnosis to avoid discharging patients in real labor. In addition, the considerable
cost to the community of incorrect diagnosis of labor should be recognized. For example, Italy's
NHS data revealed that premature diagnosis of labor resulted in 100,000 unnecessary days of
hospital admission each year.
Premature intervention (leading to unnecessary induction) and intervention at too late a stage, which
could lead to dysfunctional labor, lead to increases in the rate of cesarean section. Indeed, one of
the most common causes of the increasing rate of cesarean delivery is the failure to manage the
progression of labor. Strict criteria for diagnosing the onset of labor ought to prevent these scenarios.
On the basis of the results obtained in this study, we suggest the following are the most useful
criteria to establish the onset of labor:
1. Reduction of interval between uterine contractions
2. Abdominal pain of increasing intensity
3. Cervical effacement (≥ 50%)
4. Cervical dilation (≥ 2 cm)
Using these criteria, a clinician should be able to recognize a true labor from a false one in most
cases. Nonetheless, it must be noted that although we used strict criteria for determining onset of
labor in this study, the percentage of wrong diagnoses was still high at 16.5 % ( Table 7 ). Currently,
we are designing a study to investigate whether the use of these criteria can reduce the percentage of
wrong diagnoses of labor. As O'Driscoll said in 1973, "The most important single item in the
management of labour is diagnosis, and when the initial diagnosis is wrong all subsequent
management is likely to be wrong also."
Table 1. Criteria Not Requiring a Medical Exam
Regular intervals of uterine contractions
Decreasing interval between uterine contractions
Abdominal pain of increasing intensity
Pain relieved by walking
Changes in intestinal habits in the last 24 hours
Changes of breathing pattern and body position during contractions.
Table 2. Criteria Requiring a Medical Exam
Premature rupture of membranes
Loss of mucous plug (not due to examination or amnioscopy)
Cervical dilation and length of uterine cervix
Table 3. Results for Criteria Not Requiring a Medical Exam
Reduction in interval between contractions 211
P = .038
P > .05
Pain of increasing intensity 229
P = .042
Table 4. Results for Criteria Not Requiring a Medical Exam
Pain relieved by walking 97
P > .05
P = .047
Changes in intestinal habits 67
P > .05
Table 5. Results for Criteria Not Requiring a Medical Exam
Loss of mucous plug144
P > .05
Changes in breathing
P > .05
P > .05
Table 6. Results for Criteria Requiring a Medical Exam
Premature rupture of membranes 56
P > .05
P = .023
Cervical dilation 144
P = .018
Number of patients with
Number of patients with
incorrect diagnosis of
Number of patients in which it was not
possible to make a judgment/total
1. O'Driscoll K, Meagher B, Boylan P. Active Management of Labour. London: Mosby; 1993.
2. Gross MM, Haunschild T, Stoexen T, Methner V, Guenter HH. Women's recognition of the
spontaneous onset of labor. Birth. 2003;30:267-271.
3. Bowes WA, Thorp JM. Clinical aspects of normal and abnormal labor. In: Creasy RK,
Reznik R, Iams J (eds). Maternal-Fetal Medicine, 5th ed. Philadelphia, Pa: Elsevier Science;
4. Arukulmaran S, Chua S. Augmentation in labour. In: Ratnam SS, Ng SC, Sen DK,
Arulkumaran S (eds). Contributions to Obstetrics & Gynaecology, Vol 3. Longmans,
Singapore: Churchill Livingstone; 1994:275-292.
5. Saunders N, Spiby H. Oxytocin in active-phase abnormalities of labor: a randomized study.
Obstet Gynecol. 1990;76:475.
6. Cammu H, Van Eeckhout E. A randomised controlled trial of early versus delayed use of
amniotomy and oxytocin infusion in nulliparous labour. Br J Obstet Gynaecol.
7. Jackson DJ, Lang JM, Ecker J, Swartz WH, Heeren T. Impact of collaborative management
and early admission in labor on method of delivery. J Obstet Gynecol Neonatal Nurs.
8. Quenby S, Pierce SJ, Brigham S, Wray S. Dysfunctional labor and myometrial lactic
acidosis. Obstet Gynecol. 2004;103:718-723.
We thank Mr. Joe Benjamin for his help with translation.
A. Ragusa, MD, and Mona Mansur, MD, Department of Obstetrics & Gynecology and Women's
Health, Niguarda Hospital, Milan, Italy. Email: email@example.com
G. Borsellino, MD, and L. Maccario, MD, Department of Obstetrics and Gynaecology, Saronno
A. Zanini, MD, Department of Obstetrics and Gynaecology, Erba Hospital, Italy.
Prof. M. Musicco, PhD, Italian National Research Council.
Disclosure: Antonio Ragusa, MD, has disclosed no relevant financial relationships.
Disclosure: Mona Mansur, MD, has disclosed no relevant financial relationships.
Disclosure: Alberto Zanini, MD, has disclosed no relevant financial relationships.
Disclosure: Massimo Musicco, PhD, has disclosed no relevant financial relationships.
Disclosure: Lilia Maccario, MD, has disclosed no relevant financial relationships.
Disclosure: Giovanni Borsellino, MD, has disclosed no relevant financial relationships.