Use of multivitamins, intake of B vitamins, and risk of ovulatory infertility

Abstract

Objective: To examine whether use of multivitamins and intake of specific nutrients in multivitamins is associated with ovulatory infertility.

Design: A prospective cohort study.

Setting: The Nurses' Health Study II.

Patient(s): Eighteen thousand five hundred fifty-five married, premenopausal women without a history of infertility who attempted a pregnancy or became pregnant between 1991 and 1999.

Intervention(s): None, observational study.

Main outcome measure(s): Incident reports of infertility caused by anovulation.

Result(s): During 8 years of follow-up, 438 women reported infertility caused by ovulatory disorder. There was an inverse association between frequency of multivitamin use and ovulatory infertility. The multivariate-adjusted relative risk (95% confidence interval) of ovulatory infertility was 0.88 (0.60, 1.28) for women consuming two tablets per week or less, 0.69 (0.51, 0.95) for women consuming three to five tablets per week, and 0.59 (0.46, 0.75) for women consuming six or more tablets per week, when compared with women who did not use these supplements (P, trend <.001). Folic acid appeared to explain part of the association between multivitamin supplement use and risk of ovulatory infertility.

Conclusion(s): Regular use of multivitamin supplements may decrease the risk of ovulatory infertility.

Figure 1. Multivariate-adjusted^* relative risk of ovulatory infertility by total intake of folic acid among non-contracepting^† women

^* Adjusted for age (continuous), calendar time (4 two-year intervals), total energy intake (continuous), for body mass index (<20, 20–24.9, 25–29.9, ≥30 and missing), parity (0, 1, ≥2 and missing), smoking history (never, past 1–4 cig/day, past 5–14 cig/day, past 15–24 cig/day, past ≥ 25 cig/day or unknown amount, current 1–4 cig/day, current 5–14 cig/day, current 15–24 cig/day and current ≥ 25 cig/day or unknown amount), physical activity (<3 MET-h/wk, 3–8.9 MET-h/wk, 9–17.9 MET-h/wk, 18–26.9 MET-h/wk, 27–41.9 MET-h/wk, ≥ 42 MET-h/wk and missing), intake of alcohol (no intake, < 2 g/day, 2–4.9 g/day, ≥ 5 g/day), coffee (<1 serving/month, 1 serving/month, 2–6 servings/week, 1 serving/day, 2–3 servings/day, ≥ 4 servings/day), major types of fatty acids, protein and quintiles of iron intake. ^† Women who did not report recent use of hormonal contraception, barrier methods, intrauterine devices or spermicides.