OBJECTIVE: To establish whether the timing of delivery between 37 and 42 weeks gestation influences neonatal respiratory outcome and thus provide information which can be used to aid planning of elective delivery at term. DESIGN: All cases of respiratory distress syndrome or transient tachypnoea at term requiring admission to the neonatal intensive care unit were recorded prospectively for nine years. SETTING: Rosie Maternity Hospital, Cambridge. SUBJECTS: During this time 33,289 deliveries occurred at or after 37 weeks of gestation. MAIN OUTCOME MEASURES: This information enabled calculation of the relative risk of respiratory morbidity for respiratory distress syndrome or transient tachypnoea in relation to mode of delivery and onset of parturition for each week of gestation at term. RESULTS: The incidence of respiratory distress syndrome at term was 2.2/1000 deliveries (95% CI; 1.7-2.7). The incidence of transient tachypnoea was 5.7/1000 deliveries (95% CI; 4.9-6.5). The incidence of respiratory morbidity was significantly higher for the group delivered by caesarean section before the onset of labour (35.5/1000) compared with caesarean section during labour (12.2/1000) (odds ratio, 2.9; 95% CI 1.9-4.4; P<0.001), and compared with vaginal delivery (5.3/1000) (odds ratio, 6.8; 95% CI 5.2-8.9; P<0.001). The relative risk of neonatal respiratory morbidity for delivery by caesarean section before the onset of labour during the week 37+0 to 37+6 compared with the week 38+0 to 38+6 was 1.74 (95% CI 1.1-2.8; P<0.02) and during the week 38+0 to 38+6 compared with the week 39+0 to 39+6 was 2.4 (95% CI 1.2-4.8; P<0.02). CONCLUSIONS: A significant reduction in neonatal respiratory morbidity would be obtained if elective caesarean section was performed in the week 39+0 to 39+6 of pregnancy.

AIM: To establish whether the timing of delivery between 37 + 0 and 41 + 6 wk gestation influences neonatal respiratory outcome in elective caesarean delivery, following uncomplicated pregnancy, thus providing information that can be used to aid planning of elective delivery at term. METHODS: All pregnant women who were delivered by elective caesarean delivery at term during a 3-y period were identified from a perinatal database and compared retrospectively with pregnant women matched for week of gestation, who were vaginally delivered. Maternal characteristics, neonatal outcome, incidence of respiratory distress syndrome (RDS) and transient tachypnea of the newborn (TTN) were analysed. During this time, 1284 elective caesarean section deliveries occurred at or after 37 + 0 wk of gestation. RESULTS: Neonatal respiratory morbidity risk (odds ratio, OR), including RDS and TTN, was significantly higher in the infant group delivered by elective caesarean delivery compared with vaginal delivery (OR 2.6; 95% CI: 1.35-5.9; p<0.01). While TTN risk in caesarean delivery was not increased (OR 1.19; 95% CI: 0.58-2.4; p>0.05), the RDS risk was significantly increased (OR 5.85; 95% CI: 2.27-32.4; p<0.01). This RDS risk is greatly increased in weeks 37 + 0 to 38 + 6 (OR 12.9; 95% CI: 3.57-35.53; p<0.01). After 39 + 0 wk, there was no significant difference in RDS risk. CONCLUSIONS: Infants born by elective caesarean delivery at term are at increased risk for developing respiratory disorders compared with those born by vaginal delivery. A significant reduction in neonatal RDS would be obtained if elective caesarean delivery were performed after 39 + 0 gestational weeks of pregnancy.