The increasing BMI of first-time pregnant women is behind a rise in adverse perinatal outcomes over a 25 year time period, a new retrospective Australian study suggests.

Analysing data from one major Sydney teaching hospital, researchers found that the prevalence of overweight among women having their first baby increased from 12.7% in 1990-94 to 16.4% in 2010-14, and that of obesity rose from 4.8% to 7.3%.

More importantly they found this increase in BMI was associated with a range of adverse perinatal outcomes particularly pre-eclampsia, macrosomia and gestational diabetes. Other complications believed to have increased as a result of the maternal weight gain included caesarean deliveries, post partum haemorrhage, prematurity, admission to the special care nursery and fetal abnormalities.