Recent weight-control efforts before trying to conceive, fecundability, and ovulation among fecund women

OBJECTIVE: There is little evidence concerning how recent weight‐control efforts and weight change affect fecundability among women attempting to spontaneously conceive. We assessed weight‐control efforts and weight change in the 12 months before attempting to conceive in relation to fecundability and ovulation among gravid, eumenorrheic women. DESIGN: Secondary analysis of a multicenter, block‐randomized, doubleblind, placebo‐controlled trial to evaluate the effect of preconception daily low dose aspirin on reproductive outcomes among women with a history of pregnancy loss who were attempting to spontaneously conceive. MATERIALS AND METHODS: The analysis included 557 women who enrolled after attempting pregnancy for ≤1 menstrual cycle and had no eating disorder or medical‐related weight loss in the past year (2% underweight; 50% normal weight; 25% overweight; 23% obese). At the enrollment visit, weight and height were measured, and participants reported their 12‐month history of weight loss, weight gain, and efforts to lose, gain, or maintain weight. For up to six menstrual cycles, participants used fertility monitors and spot‐urine clinical pregnancy tests. Ovulation was defined as either a positive pregnancy test or a 2.5‐fold increase in luteinizing hormone above baseline. A discretetime Cox Proportional Hazards model estimated the fecundability odds ratio (FOR) and 95% confidence interval (CI) of a positive pregnancy test, adjusted for age, parity, maximum body mass index (BMI) in the 12 months before enrolling, time since last pregnancy loss, recent live birth, treatment assignment, education, household income, and age at menarche. A Log‐Poisson model estimated the risk ratio (RR) and 95% CI of ovulation adjusted for maximum BMI due to scarce data in some exposure categories. RESULTS: Relative to women who reported no weight‐control efforts, women who reported trying only to maintain weight had increased fecundability (cumulative pregnancy rate: 66% vs. 82%, FOR=2.17, 95% CI: 1.09‐4.32), while women who tried to lose (FOR=0.96, 95% CI: 0.68‐ 1.35) or gain weight (FOR=0.64, 95% CI: 0.31‐1.40) had similar fecundability. Relative to weight change<5% in the 12 months preconception, the FOR for weight loss ≥5% was 1.02 (95% CI: 0.69‐1.49) and for weight gain ≥5%, FOR=1.24, 95% CI: 0.92‐1.67. All categories of weight‐control effort and weight change displayed null associations with ovulation. CONCLUSIONS: Our results suggest that, among healthy, fecund women, women who try to maintain their weight have increased fecundability‐ likely through mechanisms other than ovulation‐while fecundability is not affected by efforts to gain or lose weight, or by actual weight change ≥5%, in the 12 months before attempting pregnancy.