Population attributable fractions of perinatal outcomes for nulliparous women associated with overweight and obesity, 1990-2014.

Abstract

To examine the prevalence across 25 years of overweight and obesity among nulliparous Australian women during early pregnancy; to estimate the proportions of adverse perinatal outcomes attributable to overweight and obesity in this population. Cohort study; retrospective analysis of electronic maternity data. Setting, participants: 42 582 nulliparous women with singleton pregnancies giving birth at the Royal Prince Alfred Hospital, an urban teaching hospital in Sydney, January 1990 - December 2014. Maternal body mass index (BMI), socio-demographic characteristics, and selected maternal, birth and neonatal outcomes; the proportion of adverse perinatal outcomes that could be averted by reducing the prevalence of overweight and obesity in women prior to first pregnancies (population attributable fraction, PAF). The prevalence of overweight among nulliparous pregnant women increased from 12.7% (1990-1994) to 16.4% (2010-2014); the prevalence of obesity rose from 4.8% to 7.3% in the same period, while the proportion with normal range BMIs fell from 73.5% to 68.2%. The PAFs for key adverse maternal and neonatal outcomes increased across the study period; during 2010-2014, 23.8% of pre-eclampsia, 23.4% of fetal macrosomia, and 17.0% of gestational diabetes were attributable to overweight and obesity. Were overweight and obese women to have moved down one BMI category during 2010-2014, 19% of pre-eclampsia, 15.9% of macrosomia, 14.2% of gestational diabetes, 8.5% of caesarean deliveries, 7.1% of low for gestational age birthweight, 6.8% of post partum haemorrhage, 6.5% of admissions to special care nursery, 5.8% of prematurity, and 3.8% of fetal abnormality could have been averted. Over the past 25 years, the proportions of adverse perinatal outcomes attributable to overweight and obesity have risen with the increasing prevalence of maternal overweight and obesity. A substantial proportion of these outcomes might be averted with obesity prevention strategies that reduce pre-pregnancy maternal weight.