Cumulative live birth rates after weight reduction in obese women scheduled for IVF: follow-up of a randomized controlled trial

STUDY QUESTION: Did weight reduction in obese women scheduled for IVF increase cumulative live birth rate (CLBR) after 2 years? SUMMARY ANSWER: Weight loss prior to IVF did not increase CLBR. WHAT IS KNOWN ALREADY: Few studies have investigated the effect of weight reduction in obese infertile women scheduled for IVF. In a recent randomized controlled trial (RCT), including one IVF cycle, we found no increase in live birth rate after weight reduction. Weight regain after obesity reduction treatment often occurs, and children born to obese women have a higher risk of childhood obesity. STUDY DESIGN, SIZE, DURATION: A 2-year follow-up of a multicenter, RCT running between 2012 and 2018 was performed. Out of 317 women randomized to weight reduction followed by IVF treatment or IVF treatment-only, 305 remained in the full analysis set. Of these women, 90.5% (276/305) participated in this study. PARTICIPANTS/MATERIALS, SETTING, METHODS: Nine infertility clinics in Sweden, Denmark and Iceland participated in the RCT. Obese women under 38 years of age having a BMI >= 30 and < 35 kg/m(2) were randomized to weight reduction and IVF or IVF-only. In all, 160 patients were randomized to a low calorie diet for 12 weeks and 3-5 weeks of weight stabilization, before IVF and 157 patients to IVF-only. Two years after randomization, the patients filled in a questionnaire regarding current weight, live births and ongoing pregnancies. MAIN RESULTS AND THE ROLE OF CHANCE: 42 additional live births were achieved during the follow-up in the weight reduction and IVF group, and 40 additional live births in the IVF-only group, giving a CLBR, the main outcome of this study, of 57.2% (87/152) and 53.6% (82/153), respectively (P = 0.56; odds ratio (OR) 1.16, 95% CI: 0.74-1.52). Most of the women in the weight reduction and IVF group had regained their pre-study weight after 2 years. The mean weight gain over the 2 years was 8.6 kg, while women in the IVF-only group had a mean weight loss of 1.2 kg. At the 2-year follow-up, the weight standard deviation scores of the children born in the original RCT (index cycle) were 0.218 (1.329) (mean, SD) in the weight reduction and IVF group and - 0.055 (1.271) (mean, SD) in the IVF-only group (P = 0.25; mean difference between groups, 0.327; 95% CI: -0.272 to 0.932). LIMITATIONS, REASON FOR CAUTION: All data presented in this follow-up study were self-reported by the participants, which could affect the results. A further limitation is in power for the main outcome. The study is a secondary analysis of a large RCT, where the original power calculation was based on live-birth rate after one cycle and not on CLBR. WIDER IMPLICATIONS OF THE FINDINGS: The follow-up indicates that for women with a BMI >= 30 and < 35 kg/m(2) and scheduled for IVF, the weight reduction did not increase their chance of a live birth either in the index cycle or after 2 years. It also shows that even in this highly motivated group, a regain of pre-study weight occurred.