The impact of the time interval between two successive deliveries in an obstetric unit in terms of the mode of each delivery and the rate of perinatal mortality.

Objective: To analyze the relationship of the time interval between two deliveries, done by one obstetric team, on the delivery mode of the subsequent birth; to define the length of this interval; and to evaluate this time interval as a risk factor for increased perinatal mortality in a population-based cohort.

Methods: All singleton deliveries at ≥ 24 weeks' gestation in Lower Saxony, Germany, between 2001 and 2005 (a total of 317,663 deliveries including 402 cases of perinatal mortality) were analyzed. The mode of the previous and the subsequent delivery, the time interval between the two deliveries, the time of birth, the hospital volume, and the existence of an affiliated neonatal ward were investigated.

Results: When the first vaginal delivery was <45 min, there was a reduced probability that the subsequent birth would be a cesarean section. In case of a previous cesarean section, the cesarean rate of the following birth was influenced up to 165 min. In a multivariate analysis, vaginal deliveries following an earlier vaginal birth and occurring within <45 min were associated with increased perinatal mortality. Repeated cesarean sections within <165 min were associated with increased perinatal mortality when occurring at night or on weekends.

Conclusion: A short time interval between two deliveries in an obstetric unit constitutes an independent risk factor for perinatal mortality.