Weight Loss Prior to Pregnancy and Early Gestational Glycemia: Prepare, a Randomized Clinical Trial.

Context: Women with elevated body mass index are encouraged to lose weight before pregnancy, but no trials have tested the effects of prepregnancy weight loss on risk of developing gestational diabetes.

Objective: This work aims to determine whether prepregnancy weight loss improved the early metabolic environment as measured by early gestational diabetes diagnosis.

Methods: This was a secondary analysis of a pragmatic randomized clinical trial conducted between May 2015 and October 2019 in an integrated health system that encouraged first-trimester gestational diabetes screening for high-risk women, including those with obesity. Women aged 18 to 40 years with a body mass index (BMI) greater than or equal to 27 who were planning pregnancy were randomly assigned to a behavioral weight loss intervention or usual care. Clinical care decisions and data collection were blind to condition assignment. We compared rates of diagnosis with gestational diabetes in early pregnancy between the groups using logistic regression.

Results: Of 326 participants, 168 (89 in the intervention and 79 in usual care) had singleton pregnancies during the study period. At baseline, mean age was 31.3 ± 3.5 years and BMI was 34.8 ± 5.8. Fifty-nine (66%) intervention participants and 57 (72%) usual care participants underwent early screening. Among those, intervention participants were 73% less likely to be diagnosed with gestational diabetes than usual care participants (adjusted odds ratio [aOR], 0.27; 95% CI, 0.09-0.80). There was no difference in diagnosis of gestational diabetes in later pregnancy (aOR, 1.08; 95% CI, 0.41-2.81).

Conclusion: Participation in a prepregnancy weight loss intervention led to lower rates of gestational diabetes diagnosis in early pregnancy. This suggests positive effects of prepregnancy weight loss on the early metabolic environment, a critical factor in offspring metabolic risk.