Time to pregnancy after a prepregnancy very-low-energy diet program in women with obesity: substudy of a randomized controlled trial.

Objective: To examine the impact of a prepregnancy very-low-energy diet (VLED) program on time to pregnancy in women with obesity.

Design: Substudy of a two-arm parallel group randomized controlled trial.

Setting: Multiple tertiary care centers.

Patient(s): Women 18-38 years old with obesity (body mass index 30-55 kg/m) and planning conception.

Intervention(s): One hundred sixty-four normoglycemic women with body mass index 30-55 kg/m, aged 18-38 years, and planning pregnancy were recruited through a social media platform for a two-arm randomized controlled trial. Women were allocated to a 12-week standard dietary intervention (SDI) or modified VLED. Completers of the intervention were observed for up to 48 weeks, and time to pregnancy was recorded.

Main Outcome Measure(s): The prespecified exploratory outcome for this substudy was time to pregnancy between the completion of the 12-week intervention and the date of conception.

Result(s): Maternal weight loss at the end of the 12-week intervention was 3.1% in the SDI group and 11.9% in the VLED group. In completers of the 12-week intervention, time to pregnancy was significantly shorter in the women allocated to the VLED group than in the SDI group. Post hoc analysis showed that this difference in time to conception was particularly overt within 90 days of the intervention.

Conclusion(s): A VLED program that achieves substantial weight loss before conception reduces time to pregnancy compared with an SDI in women with obesity.

Trial Registration Number: ACTRN12614001160628.