Risk of Sudden Infant Death Syndrome and Week of Gestation of Term Birth

Abstract

Objective. We sought to determine if the risk of sudden infant death syndrome (SIDS) varied according to week of delivery at term among elective and nonelective births. Design. Retrospective cohort study. Participants. All single infants live born between 37 and 42 weeks gestation in Scotland between 1992 and 1995 documented in the Scottish Morbidity Record. Outcome. Death in the first year of life where SIDS was in the principal position on the death certificate. Results. There were 202 622 eligible births and 119 deaths attributed to SIDS. Among infants delivered electively, there was no significant association between risk of SIDS and week of delivery. Among those delivered nonelectively, the risk of SIDS declined significantly with each week of gestation (odds ratio .72, 95% confidence interval .60–.86). This trend was only minimally attenuated by adjustment for maternal age, parity, smoking and socioeconomic deprivation category, infant sex, Apgar score, mode of delivery, and birth weight decile (adjusted odds ratio .78, 95% confidence interval .65–.93). Conclusions. We hypothesize that early spontaneous labor at term and SIDS may be linked because of a common association with suboptimal intrauterine environment.