Objective To evaluate predictive factors for respiratory depression at birth in infants ≥37 weeks.
Design A population-based cohort study of respiratory depression at birth at term and post-term.
Setting Nova Scotia, Canada.
Population All 126 604 nonanomalous, singleton deliveries ≥37 weeks in cephalic presentation from 1988–2002.
Methods An analysis of maternal, antenatal, intrapartum, and neonatal factors associated with respiratory depression at birth ≥37 weeks.
Main outcome measures A composite outcome of delay in initiating and maintaining respiration after birth, 5-minute Apgar score ≤ 3, or neonatal seizures due to hypoxic–ischaemic encephalopathy.
Results The rate of respiratory depression at birth with delay in respiration was 5.2/1000, with Apgar ≤ 3 1.0/1000 live births, and with neonatal seizures 0.7/1000. A composite of any of the three respiratory depressions at birth criteria showed comparable low rates with spontaneous delivery (4.4/1000) and elective caesarean (4.8/1000). Compared with elective caesarean delivery, vacuum (13.2/1000, relative risk [RR] 3.97, P < 0.001), forceps (8.8/1000, RR 1.84, P= 0.003), failed vacuum (13.3/1000, RR 2.76, P= 0.005), failed forceps (33.3/1000, RR 6.93, P < 0.001), and caesarean in labour (17.0/1000, RR 3.54, P < 0.001) had significantly higher rates of the composite outcome.
Conclusion Overall, the rate of respiratory depression at birth in the term infant was low and the serious manifestation of seizures was less than 1 in 1000. There was a significant relationship between operative delivery in labour and respiratory depression at birth.