New research published in PLoS One suggests that inter-pregnancy weight loss in normal weight women (body mass index, 18.5-25 kg/m2) during their first pregnancy can increase the risk for preterm birth in their second pregnancy; however, this association was not evident in overweight or obese women.
Researchers analysed maternity health care data for two cohorts of women registered at the University Hospital Southampton NHS Trust. The primary cohort (n=14,961) included the first and second live-birth pregnancies, whereas the secondary cohort (n=5108) included the second and third live-birth pregnancies.
The rates of premature births in the primary and secondary cohorts were 3.4 per cent and 4.2 per cent, respectively. Within the primary cohort, weight loss (>3 kg/m2) in normal weight women was associated with an increased risk for premature birth (adjusted OR [aOR], 3.50; 95% CI, 1.78-6.88; P<.001 and spontaneous premature birth ci p=".001)." within the secondary cohort weight loss>3 kg/m2) was associated with an increased risk for premature birth (aOR, 2.01; 95% CI, 1.05-3.87). However, this association was significant only when the whole cohort was analysed and not when restricted to women who were overweight or obese at second pregnancy.
The authors concluded: "The interpregnancy period is a key window of opportunity for preventative input to improve maternal health and thus outcomes. Current national guidelines encouraging obese women to lose weight before a pregnancy should be followed to reduce other maternal and offspring adverse outcomes of maternal obesity."