Elective cesarean deliveries prior to 39 weeks gestation place infants at increased risk of morbidity. Idiopathic intrauterine fetal death (IUFD) has yet to be evaluated to determine the gestational age that is most protective against fetal death. Our aim was to examine rates of IUFD and neonatal morbidity in uncomplicated term pregnancies to identify the optimal gestational age of delivery.
A retrospective case control study was performed. Inclusion criteria were singleton term pregnancies who delivered between 37 0/7 weeks to 42 6/7 weeks. Exclusion criteria were all “complicated pregnancies”: emergency deliveries, presence of maternal hypertension, diabetes, infection, fetal disease or malformations, and placental abnormalities.
19,264 maternal/infant pairs were examined. The overall rate of NICU admission was 2.7% and IUFDs was 0.20%. The lowest rate for IUFD was found at 39 weeks (0.14% of deliveries at 39 weeks). The lowest rates for NICU admission, any respiratory morbidity, and diagnosis of TTN or RDS were each found at 38 weeks gestational age. Adjusted odds ratios (with 95% confidence intervals) showed 3.48 (1.24–9.79) risk of IUFD at 37 vs 39 weeks, 2.09 (1.47–2.98) risk of NICU admission at 37 vs 38 weeks, 2.54 (1.62–3.97) risk of respiratory morbidity at 37 vs 38 weeks, and 3.38 (1.84–6.18) risk of TTN/RDS at 37 vs 38 weeks.
Neonatal respiratory morbidity was lowest for deliveries at 38–39 weeks. IUFD was 3.5 times more likely at 37 weeks vs 39 weeks, which was a significant finding. Our findings support current guidelines advising clinicians when to deliver term pregnancies.
University of Connecticut School of Medicine, Farmington, CT
Financial Disclosure: The authors did not report any potential conflicts of interest.