Is couples’ body compositions associated with reduced fecundity as measured by a longer time-to-pregnancy (TTP)?
Couples whose BMI are within obese class II (≥35 kg/m2) have a longer TTP in comparison to leaner (BMI < 25 kg/m2) couples, observed only when both partner's BMI was jointly modeled.
Extremes of BMI have been associated with a longer TTP and with less successful assisted reproductive technology (ART) outcomes. To our knowledge, the association between measured adiposity in both partners of the couple and prospectively measured TTP has not been investigated despite pregnancy being a couple-dependent outcome.
Prospective cohort with preconception recruitment of 501 couples trying for pregnancy and recruited from 16 counties in Michigan and Texas between 2005 and 2009. Couples were followed daily for up to a year of trying or until a hCG pregnancy.
In-home standardized anthropometric assessment of couples upon enrollment included measured height and weight using calibrated stadiometers and scales, and measured waist and hip circumferences. Discrete-time Cox regression was used to estimate fecundability odds ratios (FORs) and 95% CIs, controlling for potential confounders including age, number of days of vigorous physical activity, serum cotinine concentration, race, education, free cholesterol levels for each partner in partner-specific models and for both partners in couple-based models as well as average acts of intercourse per menstrual cycle and menstrual cycle regularity.
Neither male nor female partner's BMI was associated with TTP when modeled individually. However, obese class II (BMIs ≥ 35.0 kg/m2) couples experienced a reduction in fecundability in both unadjusted (FOR = 0.45; 95% CI: 0.23, 0.89) and adjusted analyses (aFOR = 0.41; 95% CI: 0.17, 0.98) resulting in a longer TTP in comparison to couples with normal BMI (<25 kg/m2). Female partners’ waist circumference ≥88.6 cm was associated with a significant reduction in fecundability in the unadjusted model (FOR = 0.64; 95% CI: 0.48, 0.86) but not in the adjusted model (aFOR = 0.77; 95% CI: 0.55, 1.08) in comparison to females with a smaller (<80 cm) circumference.
BMI and waist circumference are proxy measures of body composition and residual confounding cannot be eliminated. Findings may not be generalizable to clinical populations.
This is the first cohort study known to us with preconception enrollment of couples who underwent standardized anthropometric assessment and for whom TTP was prospectively measured. The findings underscore the importance of considering both partners’ body composition for fecundity outcomes and preconception guidance.
Supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Contracts #N01-HD-3–3355, N01-HD-3–3356 and N01-HD-3–3358). The authors have no competing interests.
- physical activity
- body mass index procedure
- chorionic gonadotropin
- body composition
- hip region
- hip joint
- human development
- menstrual cycle
- reproductive techniques, assisted
- social role
- cholesterol measurement test
- child health
- cox proportional hazards models
- waist circumference
- anthropometric characteristics assessment
- weight measurement scales