Randomized controlled trial of prepregnancy lifestyle intervention to reduce recurrence of gestational diabetes mellitus

BACKGROUND: Preconception lifestyle intervention holds potential for reducing gestational diabetes mellitus, but clinical trial data are lacking.OBJECTIVE: This study aimed to determine the effects of a prepreg-nancy weight loss intervention on gestational diabetes mellitus recurrence in women with overweight/obesity and previous gestational diabetes mellitus.STUDY DESIGN: A 2-site, randomized controlled trial comparing a prepregnancy lifestyle intervention with educational control was con-ducted between December 2017 and February 2022. A total of 199 English-and Spanish-speaking adults with overweight/obesity and pre-vious gestational diabetes mellitus were randomized to a 16-week pre-pregnancy lifestyle intervention with ongoing treatment until conception or educational control. The primary outcome was gestational diabetes mel-litus recurrence. Analyses excluded 6 participants who conceived but did not have gestational diabetes mellitus ascertained by standard methods.RESULTS: In the 63 (33%) women who conceived and had gestational diabetes mellitus ascertained (Ns=38/102 [37%] intervention vs 25/91 [28.0%] control; P=.17), those in the intervention group had significantly greater weight loss at 16 weeks compared with controls (4.8 [3.4-6.0] vs 0.7 [-0.9 to 2.3] kg; P=.001) and a greater proportion lost >5% of body weight (50.0% [17/34] vs 13.6% [3/22]; P=.005). There was no signif-icant difference in the incidence of gestational diabetes mellitus recur-rence between the intervention (57.9% [ns=23/38]) and the control group (44.0% [ns=11/25]; odds ratio, 1.8 [0.59-5.8]). Independent of group, greater prepregnancy weight loss predicted 21% lower odds of gestational diabetes mellitus recurrence (odds ratio, 0.79 [0.66-0.94]; P=.008). A = 5% weight loss before conception reduced the odds of gestational diabetes mellitus recurrence by 82% (odds ratio, 0.18 [0.04-0.88]; P=.03).CONCLUSION: Lifestyle intervention produced considerable pre-pregnancy weight loss but did not affect gestational diabetes mellitus rates. Given that the conception rate was 50% lower than expected, this study was underpowered.