Association of Obesity With Longer Time to Pregnancy

To assess whether obesity is associated with increased time to pregnancy in a cohort of participants who were stopping their contraceptive method to attempt pregnancy.

We performed a secondary analysis of the FACT (Fertility After Contraceptive Termination) study. This prospective analysis included 432 participants, aged 18-35 years, who discontinued contraception to become pregnant, were sexually active with a male partner, and provided pregnancy status data within the first 12 months in the study. The primary outcome, time to pregnancy, was measured beginning with discontinuation of contraception to estimated pregnancy date. We used Cox proportional hazard models to assess associations of normal (lower than 25.0), overweight (25.0-29.9), and obese (30 or higher) body mass index (BMI) and time to pregnancy while controlling for potential confounding factors.

After adjusting for confounders, participants with BMIs 30 or higher were noted to have prolonged time to pregnancy compared with those with BMIs lower than 25 (adjusted hazard ratio [aHR] 0.62; 95% CI 0.44-0.89). The median time to pregnancy for participants with normal BMIs was 5.3 months (95% CI 3.8-6.4) compared with 8.2 months (95% CI 6.8-10.8) for participants with obesity. Pregnancy rates at 1 year were 76.4% (95% CI 69.7-82.6%), 69.5% (95% CI 60.5-78.1%), and 59.1% (95% CI 51.0-67.4%) for participants with BMIs lower than 25, 25-29.9, and 30 or higher, respectively. Menstrual irregularity was also associated with decreased fertility (aHR 0.67; 95% CI 0.46-0.97).

Compared with participants with normal BMIs, we observed increased time to pregnancy for participants with obesity stopping contraception with the intention to become pregnant. Understanding the reasons for this association will be helpful to inform patients and guide clinical practice.

The FACT Study was funded, in part, by Bayer, CooperSurgical, and the Society of Family Planning.