We undertook a large retrospective cohort study to examine the rates of adverse perinatal outcomes in women with APA. The cohort included all women with a live, term, cephalic, singleton birth diagnosed with active phase arrest at the University of California, San Francisco (UCSF), who delivered between 1991 and 2001 (n=1,014). We excluded women with multiple gestations, delivery prior to 37 weeks gestation, and anomalous or non-viable fetuses. The Committee on Human Research at UCSF approved the study. The primary independent variable of interest was mode of delivery (vaginal delivery versus cesarean delivery). Maternal outcomes included the frequency of chorioamnionitis, endomyometritis, postpartum hemorrhage (>500ml blood loss for vaginal delivery, >1000 ml for cesarean delivery during the first 24 hours), severe postpartum hemorrhage (>1000ml blood for vaginal delivery and >1500 ml for cesarean delivery) and blood transfusion. Neonatal outcomes included 5 minute Apgar score < 7, acidemia (umbilical cord arterial pH <7.0 or umbilical artery base excess ≤−12), neonatal sepsis (as diagnosed by the managing pediatrician), and the frequency of admission to the neonatal intensive care unit (NICU).
To evaluate the risks associated with vaginal delivery in the setting of active phase arrest, we constructed an alternative cohort which included all women with term vaginal deliveries that occurred at the University of California, San Francisco (UCSF) from 1991 to 2001 (n=12,901). All women with a term, singleton, live, cephalic, non-anomalous fetus who delivered vaginally during the study period were included. As above, we excluded women with multiple gestations, preterm delivery prior to 37 weeks, cesarean delivery, and anomalous or non-viable fetuses. All deliveries during the study period were performed by the attending physicians, certified nurse midwives, or resident physicians with attending supervision.
For this cohort, the primary independent variable was the diagnosis of active phase arrest. We evaluated several outcomes. Maternal outcomes included frequency of operative vaginal delivery (including forceps and vacuum-assisted vaginal delivery), chorioamnionitis, severe (third or fourth degree) perineal lacerations, endomyometritis, post-partum hemorrhage, and blood transfusion. Neonatal outcomes examined included the frequency of 5 minute Apgar score of < 7, acidemia,, neonatal sepsis, admission to the neonatal intensive care unit (NICU), shoulder dystocia, clavicular fracture, Erb’s palsy, and cephalohematoma (as diagnosed by the pediatrician caring for the neonate).
During the study period, the diagnosis of active phase arrest was defined as absence of cervical change during the active phase of labor (≥ 4cm cervical dilation) for at least 2 hours in the presence of adequate uterine contractions (≥ 200 Montevideo units per 10-minute period, as measured by an intrauterine pressure catheter). The diagnosis of active phase arrest was made by the managing physician at the time of delivery according to these criteria. Management decisions were under weekly morbidity and mortality peer review for quality assurance according to institutional standards of care. To evaluate management strategies at our institution, we have reviewed the charts of 191 women with a diagnosis of active phase arrest and can state that 48% were expectantly managed beyond 2 hours of APA, 26% beyond 4 hours of APA, and 26% beyond 6 hours of APA.
We extracted all data from a large electronic database containing information regarding prenatal records, labor management, and perinatal outcomes that is prospectively collected, coded and maintained. All clinical data were recorded at the time of admission and delivery by the managing physicians and midwives. Trained data abstractors also perform daily chart review to ensure accurate and complete information reporting.
All data were analyzed using STATA 9.0 (StataCorp, College Station, TX, USA). Univariable analyses using t-tests and chi-square statistics were performed to compare maternal demographic variables as well as vaginal delivery rates across continuous and dichotomous predictors, respectively. A statistical significance level of p <0.05 was used. The frequencies of adverse maternal outcomes and neonatal outcomes were compared by mode of delivery using Fisher’s exact and chi-squared tests for dichotomous variables. Next, multivariable logistic regression models were constructed to control for potential confounders including maternal age, parity, maternal race/ethnicity, maternal prepregnancy BMI, prior cesarean delivery, and delivery year. Each model evaluated the risk of adverse outcome associated with cesarean delivery.
Demographic data for women with and without APA were evaluated using basic univariable comparisons, chi-square tests for dichotomous variables and Student’s t-tests for continuous variables. The rates of adverse maternal and neonatal outcomes were compared using chi-squared tests as well as by constructing relative risks and associated 95% confidence intervals (CI) associated with the diagnosis of APA for each outcome of interest.
In order to control for the effects of several confounders, we constructed multivariable logistic regression models to estimate the effect of the diagnosis of APA on each of the outcomes of interest. In all cases, covariates in the model included maternal age, parity, race/ethnicity, body mass index (BMI), Medicaid insurance status, history of prior cesarean delivery, induction of labor, epidural use, and delivery year. A single model was constructed for each outcome of interest, each evaluating the effect (adjusted odds ratio, and 95% CI) associated with a diagnosis of active phase arrest. We were not able to construct models in the instances where there were no cases of an outcome in the APA group. Model goodness-of-fit was examined using the Hosmer-Lemeshow test.