OBJECTIVE: To determine the effect of various perinatal complications [maternal diabetes (DB), chronic hypertension (CH), pregnancy-induced hypertension (PIH), prolonged rupture of membranes (PROM), intrauterine growth restriction (IUGR), abnormal presentation, low one-minute Apgar score, multiple gestation and order of delivery (for multiples)] on the risk of developing RDS.

STUDY DESIGN: This was a hospital-based cohort study of consecutive live births from 1978-1996. Maternal and neonatal variables, including standardized diagnosis of RDS by a senior neonatologist, were analysed using the Obstetrical and Neonatal Database. Multiple logistic regression was used to control for fetal sex, route of delivery, gestational age, antenatal exposure to corticosteroids as well as the other perinatal complications listed above.

RESULTS: There were 65,389 live births (including antenatal referrals) of known gestational age, 924 (1.4%) of whom developed RDS. DB, either pre-pregnancy of gestational, had no significant influence on the risk of RDS; mild PIH was protective [odds ratio (OR)=0.5 with confidence interval(CI)=0.4-0.6] but severe PIH and CH were not; PROM (≥24H) reduced the RDS risk (OR= 0.5; CI=0.4-0.7; severe IUGR (birthweight ratio <0,75) was protective (OR=0.5; CI=0.3-0.7), but mild IUGR was not; neither fetal presentation nor very low Apgar (0-3) had a significant effect on risk, but Apgar of 4-6 were unfavorable (OR=1.7; CI=1.3-2.1). First twins did not differ in risk, but second twins had a higher risk (OR=2.3; CI=1.7-3.0).

CONCLUSIONS: Contrary to usual belief, neither maternal diabetes nor severe birth asphyxia proved to be predisposing factors for RDS, nor was severe IUGR, nor severe PIH found protective. Factors associated with fetal stress are thought to be protective against RDS, but fetal stress appears to be only a partial explanation since some factors associated with fetal stress were not found protective.