Infant births during the internal night are at increased risk for operative delivery and NICU admission

The purpose of the present study was to compare neonatal morbidity between night and the rest of day and investigate potential differences of birth outcomes during the internal night.

We conducted a retrospective study based on maternal and neonatal data of period 2004-2007, enrolling exclusively spontaneous deliveries of term (≥ 37 weeks), singleton pregnancies with cephalic presentation that were in labor. Time of day was divided into the night-shift period, from 11.00 p.m. to 7.00 a.m. (period 1) and the rest-of-day period, from 7.00 a.m. to 11.00 p.m. (period 2). The night-shift period was further sub-divided into period 1a (11.00 p.m.-3.00 a.m.) and period 1b (3.00 a.m.-7.00 a.m.). Epidemiological and obstetric characteristics as well as neonatal outcomes were initially compared between periods 1 and 2 and thereafter between sub-periods 1a and 1b.

There were 3,055 cases with complete data meeting our inclusion criteria, of which 871 (28.5%) were delivered during period 1 and 2,184 (71.5%) during period 2. Furthermore, 51.3% of night-born infants were delivered during period 1a and the remaining 48.7% during period 1b. All examined parameters were not significantly different between periods 1 and 2. Analyzing night internally, the rate of emergent CS was significantly higher for period 1a (13.2%), compared with period 1b (4%). Furthermore, incidence of NICU admission was significantly higher for the first half of the night-shift period (2.7%) compared to the relative of the second half (0.5%).

Neonatal morbidity was comparable between night-shift and rest-of-day periods, but the rates of emergent CS and NICU admission were significantly increased in the first half of the night-shift period (11.00 p.m.-3.00 a.m.).