Abstract and Introduction
Abstract
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.
Introduction
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).
Table 1.
Criteria Not Requiring a Medical Exam
|
Table 2.
Criteria Requiring a Medical Exam
|
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[1] 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 oversight.
Results
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).
Table 3.
Results for Criteria Not Requiring a Medical Exam
| NulliparousN(%) | MultiparousN(%) | Odds Ratio(95%CI) | |
|---|---|---|---|
| Reduction in interval between contractions | 211(82.7%) | 137(85.1%) | 1.42(1.06-1.90)P = .038 |
| Regular contractions | 237(92.9%) | 146(90.7%) | 1.24(0.83-1.84)P > .05 |
| Pain of increasing intensity | 229(89.8%) | 142(88.2%) | 1.41(1.01-2.02)P = .042 |
Table 4.
Results for Criteria Not Requiring a Medical Exam
| NulliparousN(%) | MultiparousN(%) | Odds Ratio(95%CI) | |
|---|---|---|---|
| Pain relieved by walking | 97(38.0%) | 65(40.4%) | 0.89(0.72-1.10)P > .05 |
| Backache | 196(76.9%) | 119(73.9%) | 0.78(0.61-0.91)P = .047 |
| Changes in intestinal habits | 67(23.3%) | 57(35.4%) | 0.90(0.72-1.12)P > .05 |
Table 5.
Results for Criteria Not Requiring a Medical Exam
| NulliparousN(%) | MultiparousN(%) | Odds Ratio(95%CI) | |
|---|---|---|---|
| Loss of mucous plug | 144(56.5%) | 69(42.9%) | 1.07(0.88-1.32)P > .05 |
| Changes in breathingpattern | 201(78.8%) | 103(64.0%) | 1.11(0.88-1.40)P > .05 |
| Vomiting | 193(77%) | 129(86%) | 0.94(0.71-1.24)P > .05 |
Table 6.
Results for Criteria Requiring a Medical Exam
| NulliparousN(%) | MultiparousN(%) | Odds Ratio(95%CI) | |
|---|---|---|---|
| Premature rupture of membranes | 56(22%) | 31(19%) | 1.16(0.90-1.49)P > .05 |
| Cervical effacement | 185(72%) | 97(60%) | 1.44(1.12-1.77)P = .023 |
| Cervical dilation | 144(56%) | 121(75%) | 1.91(1.53-2.38)P = .018 |
Conclusions
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.[2] An incorrect diagnosis (10% of cases) may lead to poor management of labor and, as a consequence, unnecessary induction or prolonged labor.[3] Moreover, a proper diagnosis will surely reduce the number of unnecessary cesarean deliveries[4] 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.[7] 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.[8] 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:
Reduction of interval between uterine contractions
Abdominal pain of increasing intensity
Cervical effacement (≥ 50%)
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 7.
| Number of patients with correct diagnosisof labor/total | Number of patients with incorrect diagnosis of labor/total | Number of patients in which it was not possible to make a judgment/total |
| 320/423(75.6%) | 70/423(16.5%) | 33/423(7.8%) |
Acknowledgments
We thank Mr. Joe Benjamin for his help with translation.
Contributor Information
Alberto Zanini, Department of Obstetrics and Gynaecology, Erba Hospital, Italy.
Massimo Musicco, Italian National Research Council
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