RESUMO
BACKGROUND: Retained placenta is the most common second-trimester delivery complication. As the optimal third stage of labor duration remains undefined, complications associated with retained placentas are difficult to study. OBJECTIVE(S): To determine the optimal third stage of labor duration in second-trimester deliveries based on estimates of time-specific probabilities of placental delivery, placental intervention, and postpartum complication. STUDY DESIGN: We retrospectively studied adult women with singleton second-trimester vaginal deliveries. We identified third stage of labor duration, placental delivery method (spontaneous vs. manual/operative intervention), and indication for intervention. Postpartum complication was examined as a composite outcome. Differences among groups defined by delivery method and postpartum complication were tested using parametric and nonparametric tests. Probability curves describing the time-specific probabilities of placental delivery were derived using lifetable methods with group differences tested using the log-rank test. Probability of placental intervention and complication by time to placental delivery were examined using logistic regression with adjustment for confounders and other predictors. RESULTS: We identified 215 second-trimester placental deliveries (77% spontaneous, 23% intervention). Overall, 27% experienced postpartum complication, primarily hemorrhage (91%). Complication rates differed significantly between spontaneous placental deliveries (16%) and interventions (61%, P < 0.01). Both placental intervention and postpartum complication were strongly associated with longer time to placental delivery. Spontaneous placental deliveries occurred earlier than deliveries requiring intervention (P < 0.01). At 2 h, placental delivery rates were 93% in spontaneous deliveries and 39% in those requiring intervention. The overall postpartum complication rate for spontaneous placental deliveries (16%) was used as the threshold of tolerable risk and the criterion for placental intervention. Adjusted probability curves for deliveries of average gestational age (21.6 weeks) suggested that most patients (63.9%) may not require intervention until approximately 2 h following fetal delivery. Patients with PPROM would require intervention by 34 min, and those with intrapartum fever or delivery EBL ≥500 mL would already exceed the risk threshold at fetal delivery. CONCLUSIONS: Our study suggests that an optimal third stage of labor duration of approximately 2 h maximizes probability of spontaneous delivery and minimizes complication risk. Timing of intervention may be further individualized for patients based on maternal characteristics and intrapartum conditions.