Effectiveness of preconception weight loss interventions on fertility in women: a systematic review and meta-analysis

Importance Weight loss prior to conception is recommended for women with overweight or obesity to improve fertility outcomes, but evidence supporting this recommendation is mixed. Objective To examine the effectiveness of weight loss interventions using lifestyle modification and/or medication in women with overweight or obesity on pregnancy, live birth, and miscarriage. Data sources An electronic search of MEDLINE, Embase, Cochrane Library including Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials, and Cumulative Index to Nursing and Allied Health Literature was conducted through July 6, 2022, via Wiley. Study selection and synthesis Randomized controlled trials examining weight loss interventions through lifestyle and/or medication in women with overweight or obesity planning pregnancy were included. Random-effects meta-analysis was conducted reporting the risk ratio (RR) for each outcome. Sub-group analyses were conducted by intervention type, type of control group, fertility treatment, intervention length, and body mass index (BMI). Main outcomes Clinical pregnancy, live birth, and miscarriage events. Results A narrative review and meta-analysis was possible for 16 studies for pregnancy (n=3588), 13 for live birth (n=3329), and 11 for miscarriage (n=3248). Women randomized and exposed to a weight loss intervention were more likely to become pregnant (RR=1.24, 95% CI[1.07, 1.44] I2=59%), but not to have live birth (RR=1.19, 95% CI[0.97, 1.45] I2=69%) or miscarriage (RR=1.17, 95% CI[0.79, 1.74] I2=31%) compared to women in control groups. Subgroup analyses revealed women randomized to weight loss interventions lasting 12 weeks or fewer (n=9, RR = 1.43, 95% CI [1.13, 1.83]) and women with a BMI ≥ 35 kg/m2 (n=7, RR=1.54, 95% CI[1.18, 2.02]) were more likely to become pregnant compared to women in the control groups. Miscarriage was higher in intervention groups who underwent fertility treatment (n=8, RR 1.45, 95% CI [1.07, 1.96]). Conclusion and relevance Pregnancy rates were higher in women undergoing preconception weight loss interventions with no impact on live birth or miscarriage rates. Findings do not support one-size-fits-all recommendation for weight loss through lifestyle modification and/or medication in women with overweight or obesity immediately prior to conception to improve live birth or miscarriage outcomes.