Objective To examine whether a lifestyle intervention in pregnancy limits gestational weight gain (GWG) and provides measurable health benefits for mother and newborn.Design Randomised controlled trial.Setting Healthcare clinics of southern Norway.Population Healthy, non-diabetic, nulliparous women, aged ≥18 years, with a body mass index of ≥19 kg/m 2 , and with a singleton pregnancy at ≤20 weeks of gestation.Methods Women were randomised to an intervention group (with dietary counselling twice by telephone and access to twiceweekly exercise groups) or to a control group (with standard prenatal care). Participants were measured three times during pregnancy and at delivery, and newborns were measured at delivery. Hospital records were reviewed for outcomes of pregnancy and delivery. Assessors were blinded to group allocation. Analysis was performed by intention to treat, assessing GWG using the Student's t-test and linear mixed models, and comparing proportions using the chi-square test.Main outcome measures GWG, rates of pregnancy complications and operative deliveries, and newborn birthweight.Results A total of 606 women were randomised. Of these, 591 were analysed, with 296 in the intervention group and 295 in the control group. At term, the mean GWG from pre-pregnancy was 14.4 kg for the intervention group and 15.8 kg for the control group (mean difference 1.3 kg; 95% confidence interval, 95% CI 0.3-2.3 kg; P = 0.009). There was no significant difference between groups in the frequency of pregnancy complications or operative deliveries. The intervention demonstrated no effect on the mean birthweight of term infants, or on the proportion of large newborns.Conclusions The Norwegian Fit for Delivery lifestyle intervention in pregnancy had no measurable effect on obstetrical or neonatal outcomes, despite a modest but significant decrease in GWG.Keywords Birthweight, diet, intervention, lifestyle, physical activity, pregnancy, weight gain.Tweetable abstract Norwegian Fit for Delivery RCT: reduced gestational weight gain, unchanged birthweight and obstetric outcomes.

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 À0.77 kg, 95% CI À1.81, 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 À1.54 kg, 95% CI À3.02, À0.05; 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.