Objective: While obstetrical management has changed significantly over years, the optimal duration of the second stage of labor still remains to be defined. The purpose of this study was to evaluate the effect of the duration of labor on fetal distress and maternal perinatal morbidity.
Methods: There were 1457 consecutive patients delivered of a singleton fetus in cephalic presentation beyond the 34th week of gestation at the I. Frauenklinik, Ludwig-Maximilians University, Munich between May 1999 and June 2000. The 257 patients (17.6%), who underwent cesarean section prior to or during labor, were excluded from the study. Of the 1200 vaginal deliveries, 1017 (84.8%) were normal spontaneous deliveries, while 183 (15.2%) were instrumentally assisted. Data were contemporaneously collected and analyzed for the presence of severe pelvic floor damage, maternal hemorrhage, maternal fever, delayed involution of the uterus, fetal acidosis and APGAR score, and the necessity for admitting the newborn to the intensive care unit (NICU). A second stage duration of > 2 hr was considered to be prolonged.
Results: The mean duration of the second stage of labor was 70 min (range 2-387, SD 73 min). For 952 patients (79.3%), the second stage was less than 2 h. For 47 patients (3.9%), it exceeded 4 h. A prolonged duration of the second stage was not associated with low Apgar scores 5 and 10 min postpartum (P = 0.76 and P = 0.38, respectively), a higher incidence of umbilical artery pH levels of < 7.20 (P = 0.60), nor with an increased rate of admission to the NICU (P = 0.24). A significant increase in the rate of maternal blood loss was noted after long second stages (1.84 g/dl median difference between the intrapartum and postpartum hemoglobin level) in comparison to patients with normal duration of second stage (0.79 g/dl), both by univariate (P < 0.0001) and multivariate (P < 0.001) analysis. The incidence of third degree anal sphincter tears was significantly correlated with a prolonged duration of second stage in univariate analysis (7.7%, P = 0.001), but not in multivariate analysis after allowing for duration of the second stage, maternal age, birth weight, episiotomy, and mode of delivery (P = 0.26).
Conclusion: There is no evidence that prolonged second stage of labor is a serious disadvantage to the fetus, if adequate monitoring is provided. Because the increase of maternal morbidity in patients with prolonged labor may be partially attributed to a higher rate of operative procedures in these patients, interventions should not be solely based on the elapsed time after full cervical dilatation.