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The second stage of labor extends from complete cervical dilatation to delivery. During this stage, descent and rotation of the presenting part occur as the fetus passively negotiates its passage through the birth canal. Generally, descent begins during the deceleration phase of dilatation as the cervix is drawn upward around the fetal presenting part. The most common means of assessing the normality of the second stage of labor is to measure its duration, but progress can be more meaningfully gauged by measuring the change in fetal station as a function of time. Accurate clinical identification and evaluation of differences in patterns of fetal descent are necessary to assess second stage of labor progress and to make reasoned judgments about the need for intervention. Three distinct graphic abnormalities of the second stage of labor can be identified: protracted descent, arrest of descent, and failure of descent. All abnormalities have a strong association with cephalopelvic disproportion but may also occur in the presence of maternal obesity, uterine infection, excessive sedation, and fetal malpositions. Interpretation of the progress of fetal descent must be made in the context of other clinically discernable events and observations. These include fetal size, position, attitude, and degree of cranial molding and related evaluations of pelvic architecture and capacity to accommodate the fetus, uterine contractility, and fetal well-being. Oxytocin infusion can often resolve an arrest or failure of descent or a protracted descent caused by an inhibitory factor, such as a dense neuraxial block. It should be used only if thorough assessment of fetopelvic relationships reveals a low probability of cephalopelvic disproportion. The value of forced Valsalva pushing, fundal pressure, and routine episiotomy has been questioned. They should be used selectively and where indicated. [ABSTRACT FROM AUTHOR]

Cesarean birth has increased substantially in many parts of the world over recent decades and concerns have been raised about the propriety of this change in obstetric practice. Sometimes, a cesarean is necessary to preserve fetal and maternal health. But in balancing the risks of surgical intervention the implicit assumption has been that cesarean birth is an equivalent alternative to vaginal birth from the standpoint of the immediate and long-term health of the fetus and neonate. Increasingly, we realize this is not necessarily so. Delivery mode per se may influence short-term and abiding problems with homeostasis in offspring, quite independent of the indications for the delivery and other potentially confounding factors. The probability of developing various disorders, including respiratory compromise, obesity, immune dysfunction, and neurobehavioral disorders has been shown in some studies to be higher among individuals born by cesarean. Moreover, many of these adverse effects are not confined to the neonatal period and may develop over many years. Although the associations between delivery mode and long-term health are persuasive, their pathogenesis and causality remain uncertain. Full exploration and a clear understanding of these relationships is of great importance to the health of offspring. [ABSTRACT FROM AUTHOR]

There is no doubt that parturition can produce fetal and neonatal adversity, but the frequency with which this occurs is uncertain, particularly in modern healthcare settings. Moreover, there is a paucity of recent studies in this area. Substantial challenges impede epidemiologic study of the effect of parturition on offspring. Randomized trials would be ethically fraught. Therefore, large observational samples with detailed data concerning labor and delivery events are needed. Importantly, long-term follow-up of infants is necessary to reach reliable conclusions. Few such data sets exist, and it is difficult, expensive, and time-consuming to create and to study them. Reports of immediate newborn condition in relation to the antecedent labor are helpful, but this evidence is an imperfect predictor of long-term neurologic status. In this review, we endeavor to summarize existing information about the relationship between objectively defined abnormalities of labor progress and long-term disability in offspring. The only data available are from collected experiential information on outcomes stratified according to labor and delivery events. Most studies do not ensure against confounding by the many concurrent conditions that may affect outcome, or use inconsistent criteria to define abnormal labor. According to the best available evidence, dysfunctional labor patterns are potentially associated with poor outcomes for surviving infants. The question of whether these adverse effects can be mitigated by early diagnosis and expeditious management deserves to be answered, but cannot be at this time. In the absence of more conclusive results from well-designed studies, we can conclude that the best interests of offspring are served by adhering to evidence-based paradigms for the prompt identification and treatment of dysfunctional labor patterns. [ABSTRACT FROM AUTHOR]

The latent phase of labor extends from the initiation of labor to the onset of the active phase. Because neither margin is always precisely identifiable, the duration of the latent phase often can only be estimated. During this phase, the cervix undergoes a process of rapid remodeling, which may have begun gradually weeks before. As a consequence of extensive changes in its collagen and ground substance, the cervix softens, becomes thinner and dramatically more compliant, and may dilate modestly. All of these changes prepare the cervix for the more rapid dilatation that will occur during the active phase to follow. For the clinician, it is important to recognize that the latent phase may normally extend for many hours. The normal limit for the duration of the latent phase should be considered to be approximately 20 hours in a nullipara and 14 hours in a multipara. Factors that have been associated with a prolonged latent phase include deficient prelabor or intrapartum cervical remodeling, excessive maternal analgesia or anesthesia, maternal obesity, and chorioamnionitis. Approximately 10% of women with a prolonged latent phase are actually in false labor, and their contractions eventually abate spontaneously. The management of a prolonged latent phase involves either augmenting uterine activity with oxytocin or providing a sedative-induced period of maternal rest. Both are equally effective in advancing the labor to active phase dilatation. A very long latent phase may be a harbinger of other labor dysfunctions. [ABSTRACT FROM AUTHOR]

During labor mother and fetus are evaluated at intervals to assess their well-being and determine how the labor is progressing. These assessments require skillful physical diagnosis and the ability to translate the acquired information into meaningful prognostic decision-making. We describe a coordinated approach to the assessment of labor. Graphing of serial measurements of cervical dilatation and fetal station creates "labor curves," which provide diagnostic and prognostic information. Based on these curves we recognize nine discrete labor abnormalities. Many may be related to insufficient or disordered contractile mechanisms. Several factors are strongly associated with development of labor disorders, including cephalopelvic disproportion, excess analgesia, fetal malpositions, intrauterine infection, and maternal obesity. Clinical cephalopelvimetry involves assessing pelvic traits and predicting their effects on labor. These observations must be integrated with information derived from the labor curves. Exogenous oxytocin is widely used. It has a high therapeutic index, but is easily misused. Oxytocin treatment should be restricted to situations in which its potential benefits clearly outweigh its risks. This requires there be a documented labor dysfunction or a legitimate medical reason to shorten the labor. Normal labor and delivery pose little risk to a healthy fetus; but dysfunctional labors, especially if stimulated excessively by oxytocin or terminated by complex operative vaginal delivery, have the potential for considerable harm. Conscientiously implemented, the approach to the evaluation of labor outlined in this review will result in a reasonable cesarean rate and minimize risks that may accrue from the labor and delivery process. [ABSTRACT FROM AUTHOR]

Implementation of clinical practice guidelines may moderate health care costs, improve care, reduce medicolegal liability, and provide a uniformity in care allowing meaningful investigation of treatments and outcomes. However, new guidelines are often uncritically embraced by clinicians, risk management organizations, insurance companies, and the courts as the standard of care. Adoption of incompletely vetted recommendations can lead to patient harm. Recent recommendations made by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine for assessment and management of labor provide an example of well-intended guidelines adopted uncritically. Ideally, but unattainably, each step in a practice guideline would be supported by results of prospective randomized trials. Usually, data from lower on the hierarchy of proof are included, and the personal or institutional preferences of the guideline developers influence the final product. These multiple resources help illuminate critical issues and balance competing perspectives, but can introduce biases that become embedded in our practice. The new labor management guidelines, which were never shown to be superior (or even equivalent) to current standards, have achieved widespread acceptance. Although they provide a formula for reducing the cesarean rate, they do so without concern for their potentially adverse effects on maternal or neonatal outcome. New guidelines should be outcome-based and address how to practice obstetrics to yield the best possible results for mother and baby. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The assessment of uterine contractions is important in clinical decision-making, but the precise role for appraising contractions remains controversial. Four clinical approaches to assessing contractions are available: manual palpation; intrauterine pressure determination; external tocodynamometry; and electrohysterography. Palpation is inexpensive and harmless but requires the constant bedside presence of a trained observer. Intrauterine pressure measurement is considered the most sensitive and specific technique, and has become the standard by which other methods are judged; however, its quantitative measurements are not always precise or reproducible. Moreover, the availability of intrauterine pressure measurements does not seem to improve maternal or neonatal outcomes in most situations. External tocodynamometry is the most widely used technique. It is easy to apply and provides reasonably accurate information about the frequency and duration of contractions, but not their amplitude. It can require frequent adjustment during labor and might not work well in patients who are obese. Electrohysterography is a recently available noninvasive technology that detects uterine electrical activity using electrodes placed on the mother's abdominal wall. This approach is at least as reliable and accurate as tocodynamometry. [ABSTRACT FROM AUTHOR]

To determine if oxytocin dosage used for labor induction differed in obese and lean women, we analyzed records of patients who underwent term labor induction and delivered vaginally. Each of a cohort of 27 patients with a body mass index (BMI) >40 kg/m2 was matched with a patient with a BMI <28 kg/m2 for gestational age, for birth weight, and for cervical dilatation and fetal station at admission. The oxytocin dose administered during first stage labor was calculated for each patient. In addition to the matched characteristics, there was no difference between groups in parity, frequency of diabetes, epidural anesthesia use, or pharmacologic cervical ripening. Oxytocin utilization was significantly greater in obese women than in lean women. The maximum administration rate was 17.7±4.7 and 13.1±5.0 mU/min, respectively (P=0.001). Oxytocin administered per minute during the first stage of labor was greater in the obese group (11.6±4.8 vs. 8.6±4.1 mU/min; P=0.020). Neither active phase duration nor the maximum rate of dilatation differed significantly between the groups. That obese parturients required more oxytocin than lean women during the first stage of successful labor induction could not be explained by group differences in parity, birth weight, dysfunctional labor, pre-induction dilatation and station, or epidural use. [ABSTRACT FROM AUTHOR]

Objective To evaluate the performance of external electronic fetal heart rate and uterine contraction monitoring according to maternal body mass index. Design Secondary analysis of prospective equivalence study. Setting Three US urban teaching hospitals. Sample Seventy-four parturients with a normal term pregnancy. Methods The parent study assessed performance of two methods of external fetal heart rate monitoring (abdominal fetal electrocardiogram and Doppler ultrasound) and of uterine contraction monitoring (electrohystero-graphy and tocodynamometry) compared with internal monitoring with fetal scalp electrode and intrauterine pressure transducer. Reliability of external techniques was assessed by the success rate and positive percent agreement with internal methods. Bland-Altman analysis determined accuracy. We analyzed data from that study according to maternal body mass index. Main outcome measures We assessed the relationship between body mass index and monitor performance with linear regression, using body mass index as the independent variable and measures of reliability and accuracy as dependent variables. Results There was no significant association between maternal body mass index and any measure of reliability or accuracy for abdominal fetal electrocardiogram. By contrast, the overall positive percent agreement for Doppler ultrasound declined ( p = 0.042), and the root mean square error from the Bland-Altman analysis increased in the first stage ( p = 0.029) with increasing body mass index. Uterine contraction recordings from electrohysterography and tocodynamometry showed no significant deterioration related to maternal body mass index. Conclusions Accuracy and reliability of fetal heart rate monitoring using abdominal fetal electrocardiogram was unaffected by maternal obesity, whereas performance of ultrasound degraded directly with maternal size. Both electrohysterography and tocodynamometry were unperturbed by obesity. [ABSTRACT FROM AUTHOR]

To determine whether the effectiveness of oxytocin treatment of arrest of dilatation differed in obese compared to lean women, we did a retrospective analysis of 118 subjects in spontaneous labor whose arrest of dilatation was treated with oxytocin. Cases were stratified by maternal body mass index (BMI): Group A, <25 kg/m2; Group B, 25.0-29.9 kg/m2; Group C, 30.0-34.9 kg/m2; and Group D, ≥35 kg/m2. Groups were comparable in maternal age, parity, gestational age, birth weight, and the frequency of infection. Full dilatation was reached in about 90% of Group A and B, 72% of Group C, and 39% of Group D, the most obese women (P<0.001). The cesarean rate was directly related to maternal BMI, 11.4%, 22.9%, 34.3%, and 69.6% in Groups A through D, respectively (P<0.001). Significantly more oxytocin was used in group D than in the other groups during the first 3h of infusion in attempting to overcome the arrest (P=0.003). We conclude that oxytocin treatment of arrest of dilatation was less effective in obese than in lean women. This effect was most prominent in women with a BMI >35 kg/m2, who were, despite having received more oxytocin than those in the leaner groups, less than half as likely to attain full dilatation and more than twice as likely to deliver by cesarean. [ABSTRACT FROM AUTHOR]

Objective: To compare the accuracy and reliability of uterine contraction identification from maternal abdominal electrohysterogram and tocodynamometer with an intrauterine pressure transducer. Methods: Seventy-four term parturients had uterine contractions monitored simultaneously with electrohysterography, tocodynamometry, and intrauterine pressure measurement. Results: Electrohysterography was more reliable than tocodynamometry when compared to the intrauterine method (97.1 versus 60.9 positive percent agreement; P < 0.001). The root mean square error was lower for electrohysterography than tocodynamometry in the first stage (0.88 versus 1.22 contractions/10 minutes; P < 0.001), and equivalent to tocodynamometry in the second. The positive predictive values for tocodynamometry and electrohysterography (84.1% versus 78.7%) were not significantly different, nor were the false positive rates (21.3% versus 15.9%; P = 0.052). The sensitivity of electrohysterography was superior to that of tocodynamometry (86.0 versus 73.6%; P < 0.001). Conclusion: The electrohysterographic technique was more reliable and similar in accuracy to tocodynamometry in detecting intrapartum uterine contractions. [ABSTRACT FROM AUTHOR]

Aim: To determine whether maternal obesity is associated with dysfunctional labor patterns. Methods: In a case-control design we compared the graphic labor patterns of a group of 105 very obese subjects [body mass index (BMI) >35 kg/m2] with those of 113 lean controls (BMI<26 kg/m2). All entered spontaneous labor at term. Cases with birth weights >4 kg, diabetes mellitus, hypertension and prior cesarean delivery were excluded. Results: The obese group had a significantly higher frequency of arrest of dilatation (17.6 vs. 5.2%; P=0.005). Conclusions: Maternal obesity is associated with active phase labor dysfunction, specifically arrest of dilatation. [ABSTRACT FROM AUTHOR]

We studied changes in the width of the symphysis pubis in 32 women examined serially by ultrasound during labor. Measurements were made at the superior border of the symphysis and at its narrowest breadth in the latent phase, the active phase, and the second stage of labor. There was a significant increase in the width of the symphysis between the first and second stages of labor at both measured levels. Widening was observed in 94% at the superior symphyseal breadth and in 59% at the narrowest. Of those cases in which the width of the symphysis increased, there was a large spectrum of change, ranging from 9 to 98% of the original width at the narrowest measurement site and from 2 to 139% at the superior breadth. There was a strong inverse correlation between maternal age and the degree of symphyseal widening in nulliparas, but not in multiparas. We conclude that labor is associated with a substantial widening of the symphysis pubis in most, but not all women. [ABSTRACT FROM AUTHOR]

The ongoing debate about what models of cervical dilatation and fetal descent should guide clinical decision-making has sown uncertainty among obstetric practitioners. We previously argued that the adoption of recently published labor assessment guidelines promoted by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine may have been premature. Before accepting any new clinical approaches as the standard of care, their underlying hypotheses should be thoroughly tested to ensure they are at least equivalent (or, preferably, superior) to existing management paradigms. Some of the apparent urgency to subscribe to new clinical tactics has been fueled by legitimate concerns about the rise in the cesarean delivery rate over the past several decades. A major contributor to this change in practice patterns is that more cesarean deliveries are being done for diagnoses that fall under the rubric of dystocia than ever before. As a consequence, traditional labor curves-fundamental for assessing labor progress-and the practice paradigms associated with them have received intense scrutiny as a possible contributor to this delivery trend. Moreover, the recent proposal of new labor curves and accompanying management guidelines has, understandably, fed the appetite to correct a perceived problem. However, the cesarean delivery rate rose most rapidly during decades when there was no major change in traditional labor curves or in the guidelines for their interpretation. Also, during the years since the new guidelines were first published, there has been no major fall in cesarean delivery frequency. This raises the question of whether there was truly a fundamental flaw in the traditional labor management paradigms or whether their proper interpretation and use had been somehow forgotten, ignored, or corrupted. More important, existing studies have shown that application of the new guidelines often (but not always) results in a modest fall in the cesarean delivery rate, but that this change may be accompanied by significant increases in maternal and neonatal morbidity. These results strongly suggest more caution in the adoption of the American College of Obstetricians and Gynecologists / Society for Maternal-Fetal Medicine labor assessment recommendations. They are based on a hypothesis that has yet to undergo thorough evaluation of its risks and benefits. [ABSTRACT FROM AUTHOR]