Excess weight in women, men ups risk of subfertility and pregnancy loss

For both women and men, BMI that is outside of the normal category during the preconception or early-pregnancy periods is a risk factor for lower fecundability, subfertility, and miscarriage, as reported in a cohort study.

The study included 3,604 women and their partners who were followed from the preconception period up until birth. BMI was measured in preconception or early pregnancy. The main outcomes such as fecundability (ie, the probability of conceiving within 1 month), subfertility (ie, time to pregnancy or duration of actively pursuing pregnancy of more than 12 months or use of assisted reproductive technology), and miscarriage (ie, pregnancy loss before 22 weeks of gestation) were assessed using questionnaires and via the obstetric caregiver.

Time-to-pregnancy analyses comprised 3,033 pregnancy episodes among women (median age 31.6 years, median BMI 23.5 kg/m²) and 2,288 episodes among men (median age 33.4 years, median BMI 24.9 kg/m²). Miscarriage analyses included 2,770 pregnancy episodes among women (median age 31.5 years, median BMI 23.5 kg/m²) and 2,189 pregnancy episodes among men (median age 33.5 years, median BMI 25.0 kg/m²).

Results showed that BMI in women and men was inversely associated with fecundability, such that fecundability decreased by 1–2 percent for every unit increase in BMI (women: fecundability ratio [FR], 0.98, 95 percent confidence interval [CI], 0.97–0.99; men: FR, 0.99, 95 percent CI, 0.98–1.00).

Among women, fecundability was lower for those with overweight (FR, 0.88, 95 percent CI, 0.80–0.98) and obesity (FR, 0.72, 95 percent CI, 0.63–0.82) relative to those who had normal weight. Subfertility was also more likely among women with overweight (odds ratio [OR], 1.35, 95 percent CI, 1.11–1.63), obesity (OR, 1.67, 95 percent CI, 1.30–2.13), and underweight (OR, 1.88, 95 percent CI, 1.22–2.88). Likewise, the odds of miscarriage were greater among women with overweight (OR, 1.49, 95 percent CI, 1.12–1.98) and obesity (OR, 1.44, 95 percent CI, 1.00–2.08).

Among men, those with obesity had increased odds of subfertility compared with those who had normal weight (OR, 1.69, 95 percent CI, 1.24–2.31).