Maternal and Neonatal Morbidity After 4 and 6 Hours of Protracted Active Labor in Nulliparous Term Pregnancies

Abstract

OBJECTIVE: 

To evaluate whether women with protracted active phase labor longer than 6 hours have an increased risk of adverse maternal and neonatal outcomes after the implementation of new labor management guidelines.

METHODS: 

This was a retrospective study of nulliparous, term, singleton, vertex deliveries at Cedars Sinai Medical Center from August 2016 to September 2017. Women were included if they progressed to active phase labor, defined by cervical dilation of 6 cm or more. Women then were divided into three groups based on the time course of cervical change between 6 and 10 cm: 1) normal active phase: cervical change 1 cm or more within 4 hours throughout active labor; 2) mildly protracted active phase: cervical change 1 cm or less over 4–6 hours; and 3) very protracted active phase: cervical change 1 cm or less over 6 hours. Rate of change was assessed between cervical examinations. Primary outcome was a composite of maternal morbidity by study group. Secondary outcome was a composite of neonatal morbidity. We hypothesized that women with very protracted active phase had higher rates of adverse outcomes when compared with normal active phase. Regression analyses were performed to compare maternal and neonatal outcomes by study group.

RESULTS: 

There were 2,559 deliveries, of which 2,378 (90.8%) were vaginal deliveries. Composite maternal and neonatal morbidity was higher with longer labor. Maternal morbidity—very protracted active phase (42.0%) compared with normal active phase (22.6%) adjusted odds ratio (aOR) 2.15 (95% CI 1.62–2.86); mildly protracted active phase (39.5%) compared with normal active phase (22.6%) aOR 2.18 (95% CI 1.67–2.84). Neonatal morbidity: very protracted active phase (19.8%) compared with normal active phase (13.8%) aOR 1.38 (95% CI 0.98–1.96); mildly protracted active phase (19.4%) compared with normal active phase (13.8%) aOR 1.44; (95% CI 1.04–1.99). Composite maternal and neonatal morbidity was not different between mildly protracted and very protracted groups.

CONCLUSION: 

Composite maternal morbidity was greater in women with cervical change consistent with mildly protracted (4–6 hours) and very protracted (more than 6 hours) labor compared with cervical change in the normal active phase (less than 4 hours) group. However, composite maternal and neonatal morbidity was not different between mildly protracted and very protracted groups.

In Brief

Maternal and neonatal morbidity increases when active labor is protracted 4 hours or more in nulliparous, term, singleton, vertex deliveries.

The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) formulated new labor management guidelines in 2014 to decrease the number of primary cesarean deliveries.¹ The ACOG–SMFM guidelines were updated to reflect contemporary data from the Consortium for Safe Labor² and included:

• 1) Active phase of labor starts after 6 cm dilation, not after 4 cm as described by Emanuel Friedman.^3–5
• 2) Arrest of dilation was defined as no cervical change despite 4 hours of adequate uterine contractions or no cervical change despite 6 hours of oxytocin administration with inadequate uterine activity.¹

Labors are now longer and there is limited data on maternal and neonatal outcomes among pregnancies managed in accordance with these updated guidelines. Historically, prolonged labor has been associated with adverse maternal and neonatal outcomes,^6–10 hence clinicians have raised concerns regarding the new labor guidelines.^11–16 However, Rouse et al demonstrated that nulliparous women were more likely to deliver vaginally, without an increase in adverse outcomes if oxytocin was continued for 4 hours without cervical change.^17,18 In the current study using the new guidelines, we sought to evaluate whether adverse maternal and neonatal outcomes are increased among women with protracted active phase. We hypothesize that adverse maternal and neonatal outcomes are increased in women with very protracted active labor defined by reaching 6 cm dilation and cervical change 1 cm or less over 6 hours or more, compared with women with cervical change 1 cm or less over 4–6 hours (mild protraction), or cervical change 1 cm or more within 4 hours (normal active phase).

METHODS

We obtained Cedars-Sinai Institutional Review Board approval to perform a retrospective cohort study of all women who were nulliparous, term, singleton, vertex presentation and delivered at Cedars-Sinai Medical Center between August 2016 and September 2017. We included all nulliparous, term, singleton, vertex women who were at least 37 weeks of gestation, and achieved cervical dilation 6 cm or more. Women with the following conditions were excluded: 10 cm dilated on admission, cesarean delivery before 6 cm dilation, any cesarean delivery without labor, fetal anomalies, and fetal demise.

Maternal demographic data including age, race–ethnicity, insurance, body mass index (BMI, calculated as weight in kilograms divided by height in meters squared), drug use, induction of labor, mode of delivery and maternal comorbidities were abstracted from the electronic medical record. Labor was managed at the discretion of the health care provider. Low dose oxytocin protocol was used in our hospital. As per institutional guidelines, ACOG–SMFM criteria for cesarean delivery had to be met, or physician explanation had to be documented regarding indications for the cesarean delivery that did not meet the criteria. Cervical examination measurements, and the consecutive times the examinations were performed, were abstracted from labor and delivery flowsheets. A study investigator (S.G.) reviewed all cervical examinations (date, time, dilation) and women were divided into three groups based on the maximum time taken for 1 cm cervical change at any point between 6 and 10 cm cervical dilation. Women who underwent cesarean deliveries were assigned to the corresponding group based on the rate of cervical change from the previous examination. The three groups were categorized as follows:

1. Normal active phase: cervical change of 1 cm or more in less than 4 hours throughout active labor
2. Mildly protracted active phase: cervical change of 1 cm or less between 4 and 6 hours
3. Very protracted active phase: cervical change of 1 cm or less in more than 6 hours of active labor

Rate of change was assessed between cervical examinations, which were performed at the discretion of the provider.

For example, if a patient had progressed (without any protraction) from 6 to 7 cm in 3 hours, she would be in normal active phase group. If a patient had progressed from 6 to 7 cm in 2 hours, but 7–8 in 5 hours she would be in mildly protracted active phase group. If a patient had progressed from 6 to 7 cm in 7 hours, and 7–8 in 1 hour, she would be in the very protracted active phase group. Very protracted active phase group is the primary study group and normal active phase and mildly protracted active phase are comparison groups.

Our primary outcome was maternal morbidity, defined by a composite measure of adverse outcomes, including maternal fever (chorioamnionitis or endometritis), postpartum hemorrhage, any blood transfusion, and postpartum length of hospital stay 5 days or more. Postpartum hemorrhage was determined by International Classification of Diseases, 10th Revision (ICD-10) codes with validation by use of uterotonic agents other than oxytocin. Similarly, maternal fever was determined by ICD-10 code and validated by maternal temperature of 100.4°F or higher with administration of appropriate antibiotics. Our secondary outcome was neonatal morbidity defined as a composite of adverse outcomes, including admission to the neonatal intensive care unit (NICU), fever, sepsis, respiratory distress syndrome, transient tachypnea of the newborn, 5-minute Apgar score of 3 or less, hypoxic ischemic encephalopathy, therapeutic hypothermia, intubation, or overall length of stay more than 5 days. All diagnoses were extracted from electronic medical record using ICD-10 codes.¹⁹

For statistical analysis, we used χ² or Fisher exact tests for categorical variables, and analysis of variance or Wilcoxon rank sum tests for continuous variables, as determined by data distribution. Multivariable logistic regression was performed to examine the association between the labor time group and composite adverse maternal and neonatal outcome, adjusting for maternal age (continuous), maternal BMI (continuous), race and ethnicity (Latina, white, black, Asian, other), insurance (government vs private), and maternal comorbidities (yes or no to any of the following: hypertension, diabetes, asthma, endocrine, gastrointestinal, neurologic disorders). We also performed the above regression analysis stratified by method of delivery. To address data sparsity, we employed exact logistic regression when appropriate. We performed a secondary analysis of women who reached the second stage compared with those who did not. All analyses were performed using SAS 9.4, and P<.05 was considered statistically significant.

RESULTS

A total of 3,166 nulliparous, term, singleton, vertex women delivered between August 2016 and September 2017. After exclusions, we identified 2,559 women who were at least 6 cm dilated and were included in the analysis (Fig. 1). Demographic information for patients in the three groups are shown in Table 1. Women with normal active phase were younger, more often white, and had lower BMIs. Women with very protracted active phase were more often induced and were more likely to have maternal comorbidities. The maximum time required for 1 cm of cervical change with normal active phase, mildly protracted active phase, very protracted active phase was mean (±SD) 74±50.7, 281±52.2 and 487±156.4 minutes, respectively.

Fig. 1.: Flow diagram for patient inclusion in the study.Govindappagari. Maternal and Neonatal Outcomes With Protracted Labor. Obstet Gynecol 2019.

Table 1.: Demographics and Baseline Characteristics by Rate of Cervical Change of 1 cm or More (N=2,559 Deliveries)

The vaginal delivery rate for our study population was 90.8%. Table 2 lists individual maternal outcomes by group. Increased time to make 1 cm change was inversely associated with spontaneous vaginal delivery. Vaginal delivery rates with normal active phase, mildly protracted active phase and very protracted active phase were 94.9%, 78.2%, and 64.2% respectively (P<.001). In univariate analyses, women with very protracted active phase, had significantly higher rates of maternal fever (P<.001), postpartum hemorrhage (P=.005), blood transfusion (P=.01) and operative vaginal delivery (P=.004) when compared with normal active phase (Table 2). Again, there was no difference between mildly protracted and very protracted groups.

Table 2.: Individual Maternal Outcomes by Rate of Cervical Change of 1 cm or More (N=2,559 Deliveries)

Table 3 describes the results of the adjusted and unadjusted primary and secondary outcomes. In the adjusted analyses, the composite maternal outcome was not different between the very protracted (42.0%) and mildly protracted (39.5%) groups (adjusted odds ratio [aOR] 0.95, 95% CI 0.69–1.42). However, composite maternal morbidity was at least twofold higher in the protracted labor group compared with normal active phase (very protracted active phase vs normal active phase aOR 2.15, 95% CI 1.62–2.86; mildly protracted active phase vs normal active phase aOR 2.18, 95% CI 1.67–2.84).

Table 3.: Unadjusted and Adjusted Composite Maternal and Neonatal Outcomes by Rate of Cervical Change of 1 cm or More (N=2,559 Deliveries)

Likewise, composite neonatal morbidity was not different between the very protracted (19.8%) and mildly protracted (19.4%) groups (aOR 0.96, 95% CI 0.62–1.48). However, composite neonatal morbidity was significantly higher with mildly protracted active phase when compared with normal active phase (aOR 1.44, 95% CI 1.04–1.99). Composite neonatal morbidity was not different with very protracted active phase when compared with normal active phase (aOR 1.38, 95% CI 0.98–1.96) (Table 3).

We evaluated rates of maternal and neonatal outcomes stratified by mode of delivery (Table 4). Among women who delivered vaginally, maternal outcomes were not different between the two protracted active phase groups. Maternal fever remained higher with very protracted active phase (27.6%) when compared with normal active phase (12.2%); (P<.001). Other outcomes were not different. However, there was no difference in maternal outcomes for women delivered by cesarean by study group.

Table 4.: Maternal Outcomes by Rate of Cervical Change Group, Stratified by Mode of Delivery

Individual neonatal outcomes included in the composite are shown in Table 5. Neonatal intensive care unit admission very protracted active phase (12.8%) compared with normal active phase (8.1%); P=.003, and length of stay (P<.001) were significantly higher with very protracted active phase when compared with normal active phase (Table 5). No difference was identified between mildly protracted and very protracted groups.

Table 5.: Individual Neonatal Outcomes by Rate of Cervical Change of 1 cm or More in Univariate Analysis (N=2,559), All Deliveries

We performed a secondary analysis to evaluate whether experiencing the second stage of labor, or length of second stage influenced the study findings. Among all the women who reached second stage (n=2,451), composite maternal morbidity was higher in the cesarean delivery group (46.9%) when compared with the vaginal delivery group (23.9%). Among women who delivered vaginally, composite maternal morbidity was significantly higher with very protracted active phase (37.8%), when compared with normal active phase (21.2%) and mildly active phase (36.7%) when compared with normal active phase (21.2%); P<.001. However, there was no difference in composite maternal morbidity by study group if delivered by cesarean (Table 6). Composite neonatal morbidity did not differ by group, route of delivery, or presence and duration of second stage (Table 7). Likewise, among women who did not reach the second stage, there was no difference in composite maternal and neonatal morbidity by study group (data not shown).

Table 6.: Composite Maternal Outcomes by Cervical Change Group (n=2,451), Women Who Reached Second Stage

Table 7.: Composite Newborn Outcomes by Cervical Change Group (n=2,451), Women Who Reached Second Stage

DISCUSSION

Among women who achieved active phase labor, maternal and neonatal outcomes were not different between the protracted labor groups (ie, when 1 cm or less cervical change was made in 4–6 hours or more than 6 hours). The odds of composite maternal morbidity were twofold higher, and neonatal morbidity was one and a half times higher in women who made 1 cm or less cervical change over 4 or more hours (mildly protracted and very protracted) compared with women with cervical change of 1 cm or more within 4 hours (normal active phase). The overall vaginal delivery rate in our cohort was 91%. Women in group one with the fastest rate of change had the highest likelihood of vaginal delivery (94.9%) and the lowest composite adverse maternal or neonatal outcomes. Women in the mildly protracted (4–6 hours) also had a relatively high likelihood of vaginal delivery (78.2%), which was higher than the 56% rate reported by Rouse et al.¹⁷

When vaginal and cesarean deliveries were analyzed separately, only maternal fever in vaginal deliveries remains significantly different between the groups suggesting that the maternal composite outcome is driven primarily by maternal fever. Many of our findings related to increased morbidity and labor duration are consistent with previous studies in the literature. For example, higher rates of maternal fever and operative vaginal delivery have been associated with prolonged active phase of labor.^{10,17,20–22} The relationship between postpartum hemorrhage and long labors is inconsistent in the literature, and we did not find this association similar to others.^17,21,22 We did not find increased rates of postpartum hemorrhage after the implementation of new labor management guidelines similar to several other studies^23–25, although some others have reported contradicting results.^26–28

One other significant finding in our study was, among women delivered by cesarean, there was no difference in maternal or neonatal outcomes based on rate of cervical change, suggesting that performing a cesarean delivery earlier may not have improved outcomes. Alternatively, waiting the additional time (more than 6 hours), may increase likelihood of vaginal delivery without additional harm.

Our findings of increased NICU admission and prolonged hospitalization with prolonged labor were similar to other studies.^21,22,28 Similar to prior studies, we did not identify a relationship between prolonged labor and respiratory morbidity.^17,20,22

Our study has several strengths. Although there are numerous studies published on prolonged active phase, and prolonged second stage, our study looked at the rate of cervical change per hour, using common cut-offs for clinical decision making. We used 6 cm of cervical dilation as active phase. Our study population was exclusively nulliparous women, whereas some others included nulliparous and multiparous women.

Our study is not without limitations. It is a retrospective, single center study and the results might not be generalizable. We did not include additional information regarding labor management such as induction methods, membrane status, Pitocin use, adequacy of uterine contractions or types of analgesia. We found increased NICU admissions in women with protracted active labor, but we cannot ascertain that protracted active phase is the etiology for these findings. For example, NICU admission could have been for neonatal hypoglycemia or causes unrelated to the labor process itself. Further, although other investigators have found increased rates of maternal fever is associated with prolonged labors, we did not evaluate when the fever occurred relative to maternal stage in labor, nor link maternal diagnoses with neonatal outcomes. Chorioamnionitis in preterm gestation can result in fetal inflammatory response and release of cytokines. This can lead to adverse neurologic outcomes including cerebral palsy.^29–32 However, long-term neonatal neurologic sequelae of chorioamnionitis in term neonates remain unclear.^33–35 Further prospective studies with long-term neonatal follow up are warranted to understand the effects of chorioamnionitis on fetal brain.

In conclusion, there did not appear to be additional risk of adverse maternal or neonatal morbidity after cervical change 1 cm or less in 4–6 hours compared with more than 6 hours (very protracted active phase vs mildly protracted active phase). However, we found that women with cervical change of 1 cm or less in more than 4 hours (ie, protracted active phase) were at higher risk for maternal fever and NICU admission compared with women with normal active phase. These findings support ACOG–SMFM recommendations to allow labor to continue for at least 6 hours after a woman has reached 6 cm before calling an arrest disorder and proceeding to cesarean delivery. We suggest that maternal and neonatal morbidity measures should be linked as a dyad and monitored concurrently as balancing measures as women are allowed to have longer labors to achieve lower nulliparous, term, singleton, vertex cesarean delivery rates.