The effect of prenatal lifestyle intervention on weight retention 12 months postpartum: results of the Norwegian Fit for Delivery randomised controlled trial

Objective To examine the effect of a prenatal lifestyle intervention on postpartum weight retention (PPWR). Design Randomised controlled trial. Setting Healthcare clinics in southern Norway. Population Healthy, nulliparous women with body mass index >= 19 kg/m(2), age >= 18 years, and singleton pregnancy of <= 20 gestational weeks. Methods Women were randomised to intervention (dietary counselling twice by phone and access to twice-weekly exercise groups during pregnancy) or control group (standard prenatal care). Intervention compliance was defined post-factum as attending dietary counselling and >= 14 exercise classes. Main outcome measures PPWR (weight measured postpartum minus self-reported pre-pregnancy weight) and the proportion of women returning to pre-pregnancy weight. Results Of 606 women randomised, 591 were included in an intention-to-treat analysis of pregnancy outcomes and 391 (64.5%) were analysed 12 months postpartum. Mean PPWR was not significantly different between groups (0.66 kg for intervention versus 1.42 kg for control group, mean difference -0.77 kg, 95% CI -1.81, 0.28; P = 0.149). An increased proportion of intervention participants achieved pre-pregnancy weight (53% versus 43%, OR 1.50, 95% CI 1.003, 1.471; P = 0.045). However, the difference was not statistically significant when we adjusted for missing data (adjusted odds ratio (OR) 2.23, P = 0.067) using logistic mixed-effects models analysis. Women compliant with intervention had significantly lower PPWR than control participants, also after adjusting for potential confounders (adjusted mean diff -1.54 kg, 95% CI -3.02, -0.05; P = 0.039). Conclusions The Norwegian Fit for Delivery intervention had little effect on PPWR, although women who were compliant with the intervention demonstrated significantly lower PPWR at 12 months.