Background More than half of women who die during pregnancy, childbirth or puerperium are either obese or overweight. Pregnancy offers the opportunity to intervene for the prevention of obesity with the aim of reducing maternal and fetal morbidity and mortality. While reduction in weight gain or weight loss may be of benefit there is a potential for harm due to weight loss itself or due to the interventions.

Aim (1) To determine the effectiveness of various interventions that prevents or treats obesity on maternal weight and other maternal and fetal outcomes.

(2) To evaluate the potential adverse effects in mother and baby due to the intervention or weight change in pregnancy

Methods We searched MEDLINE, EMBASE, BIOSIS, LILACS and Cochrane for citations on the effectiveness and harm of interventions. The relevant outcomes important to decision making were prioritised and their quality evaluated using GRADE methodology.

Results 89 studies including 40 randomised controlled trials were included. There was a statistically significant reduction in the weight gained in pregnancy in the intervention group compared to the control group (mean difference −1.4 kg; 95% CI 1.9 to 0.79), p<0.00001. There was a significant reduction in macrosomia than standard care. (RR 0.63, 95% CI 0.42 to 0.96), p=0.03. The results of other outcomes including adverse effects will be presented in detail if the abstract is selected for oral presentation.

Conclusion Dietary and life style interventions in pregnancy are effective in reducing weight gain. They also show a beneficial effect in reducing macrosomia, pre-eclampsia and birth weight.