793: Obstetric and Neonatal Outcomes in Prolonged Pregnancies at or Beyond 42 Weeks’ Gestation.

A Cochrane review on labor induction concludes that induction at or beyond term compared with expectant management is associated with fewer perinatal deaths and fewer cesarean sections (CS). The optimal timing of induction has yet to be determined; our experience is that spontaneous onset of labor is associated with a lower CS rate at all gestational ages. With that in mind we sought to examine both obstetric intervention rates and rates of perinatal mortality and morbidity in pregnancies that reach 42 weeks’ gestation. A review of all cases of prolonged pregnancies defined as ≥42 weeks’ gestation over a 10 year period from 2007 to 2016 was performed. All demographic and delivery details were entered prospectively into a computerized database; these data are subject to continuous audit. At our institution pregnancies reaching 41 weeks+5 days undergo a formal ultrasound for biophysical profile; once reassuring induction is offered at 42 weeks’ gestation. All spontaneous labors are managed in a standardized fashion according to active management of labor principles. We examined the incidence and outcome of prolonged pregnancies and compared them to the background institutional rate. Specific details, including radiology reports and placental pathology where available, were gathered for all cases of perinatal mortality, neonatal encephalopathy (NE) and hypoxic ischemic encephalopathy (HIE). Over the study period 90,564 mothers delivered infants weighing ≥500g. 4791 pregnancies reached 42 weeks’, an incidence of 4.8%. Of these, 87.7% underwent induction of labor, 2.4% had a pre-labour CS and 9.9% labored spontaneously. Labor and delivery details are inTable 1. The overall CS rate was 25.9% compared to 22.1% (p<0.0001, 95% CI 3.7-3.9). The CS rate in nulliparous women ≥42 weeks was 33% compared to 24.1% (p<0.0001, 95% CI 8.8-8.9). There were 10 perinatal mortalities in the group, an uncorrected perinatal mortality rate (PNMR) of 1.89 +- 2.29. The institutional uncorrected PNMR during that period was 6.93 +-1.25 (p<0.0001, 95% CI -5.07—5.07). Of these 10 cases, 8 had a congenital abnormality. There were 16 cases of HIE/NE; a detailed breakdown of these is contained in Table 2. Pregnancies that reach 42 weeks have a CS rate of 33% but a low perinatal mortality and morbidity rate. The CS rate remained lower for women who spontaneously labored even at 42 weeks’ gestation, supporting our policy of expectant management to control CS rates.View Large Image Figure ViewerDownload Hi-res image Download (PPT)