Body mass index, physical activity and fecundability in a North American preconception cohort study

In this preconception cohort study, overall and central obesity were associated with reduced fertility. Moderate exercise was associated with improved fertility, as was vigorous exercise, but only among overweight/obese women.

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Volume 106, Issue 2, Pages 451-459

Authors:

Craig J. McKinnon, M.P.H., Elizabeth E. Hatch, Ph.D., Kenneth J. Rothman, Dr.P.H., Ellen M. Mikkelsen, Ph.D., Amelia K. Wesselink, M.P.H., Kristen A. Hahn, Ph.D., Lauren A. Wise, Sc.D.

Abstract:

Objective

To evaluate the association between adiposity, physical activity (PA), and fecundability.

Design

Prospective cohort study.

Setting

Not applicable.

Patient(s)

A total of 2,062 female pregnancy planners from the United States and Canada who were enrolled during the preconception period.

Intervention(s)

None.

Main Outcome Measure(s)

Self-reported pregnancy. Fecundability ratios (FRs) and 95% confidence intervals (CIs) were estimated using proportional probabilities models that adjusted for potential confounders.

Result(s)

Relative to body mass index (BMI) 18.5–24 kg/m2, FRs for BMI <18.5, 25–29, 30–34, 35–39, 40–44, and ≥45 kg/m2 were 1.05 (95% CI 0.76–1.46), 1.01 (95% CI 0.89–1.15), 0.98 (95% CI 0.82–1.18), 0.78 (95% CI 0.60–1.02), 0.61 (95% CI 0.42–0.88), and 0.42 (95% CI 0.23–0.76), respectively. Reduced fecundability was observed among women with the largest waist-to-hip ratios (≥0.85 vs. <0.75; FR = 0.87, 95% CI 0.74–1.01) and waist circumferences (≥36 vs. <26 inches [≥90 vs. <66 cm]; FR = 0.80, 95% CI 0.59–1.01). Tendency to gain weight in the chest/shoulders (FR = 0.63, 95% CI 0.36–1.08) and waist/stomach (FR = 0.90, 95% CI 0.79–1.02), relative to hips/thighs, was associated with lower fecundability. Moderate PA was associated with increased fecundability (≥5 vs. <1 h/wk; FR = 1.26, 95% CI 0.96–1.65), but there was no dose-response relation. Among overweight/obese women (BMI ≥25 kg/m2), fecundability was 27% higher for vigorous PA of ≥5 versus <1 h/wk (95% CI 1.02–1.57).

Conclusion(s)

Various measures of overall and central adiposity were associated with decreased fertility among pregnancy planners. Vigorous PA was associated with improved fertility among overweight and obese women only; moderate PA was associated with improved fertility among all women.


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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders. The journal publishes juried original scientific articles in clinical and laboratory research relevant to reproductive endocrinology, urology, andrology, physiology, immunology, genetics, contraception, and menopause. Fertility and Sterility® encourages and supports meaningful basic and clinical research, and facilitates and promotes excellence in professional education, in the field of reproductive medicine.

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