Preconception Vitamin D Concentrations and Pregnancy Outcomes

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Because Vitamin D receptors are found in reproductive organs such as ovaries, uterus, and placenta, it is hypothesized that Vitamin D plays a role in reproductive function.
Because Vitamin D receptors are found in reproductive organs such as ovaries, uterus, and placenta, it is hypothesized that Vitamin D plays a role in reproductive function.

Women who previously experienced pregnancy losses demonstrated an increase in pregnancies and livebirths with sufficient preconception vitamin D concentrations, according to a study published in The Lancet Diabetes & Endocrinology.

This secondary analysis of a prospective cohort study sought to investigate the influence of vitamin D on fecundity, livebirth, and pregnancy loss by exploring the association between preconception 25-hydroxyvitamin D concentrations and pregnancy outcomes in women with proven fecundity.

The study cohort included 1191 women between 18 and 40 years who participated in the Effects of Aspirin in Gestation and Reproduction trial, and who had experienced 1 to 2 previous pregnancy losses. Between June 15, 2007, to July 15, 2011, participating women were recruited from 4 clinical sites in the United States and were followed for up to 6 menstrual cycles while attempting pregnancy and throughout pregnancy if they conceived.

Serum 25-hydroxyvitamin D samples were collected and measured at baseline (preconception) and at 8 weeks of gestation among women who conceived. Clinical outcomes of interest included clinical pregnancy, time to pregnancy (defined by the number of menstrual cycles prior to confirming pregnancy), pregnancy loss, and livebirth.

Women were classified as vitamin D sufficient or insufficient at baseline: 555 women had sufficient 25-hydroxyvitamin D concentrations (≥75 nmol/L) and 636 had insufficient concentrations (<75 nmol/L). The study found women with sufficient preconception 25-hydroxyvitamin D had lower body mass indexes, reached a higher education level, and were more likely to be white; age, multivitamin use, smoking, and previous livebirths were not associated with vitamin D concentrations. Vitamin D sufficient women demonstrated a higher frequency of achieving clinical pregnancy and livebirth than women who were vitamin D insufficient.

While the frequency of pregnancy losses was similar in both sufficient and insufficient vitamin D groups, women who suffered pregnancy losses had lower 25-hydroxyvitamin D concentrations compared with other women within their group. Another finding of the study showed that on average, vitamin D concentrations measured at preconception and at 8 weeks of gestation were similar; however, 13% of women who conceived went from a sufficient to insufficient status, and 18% went from an insufficient to sufficient status during these time points. After 8 weeks of gestation, 25-hydroxyvitamin D concentrations were not associated with pregnancy loss.

Limitations of the study included the lack of measurements related to vitamin D status, including calcitriol and genetic factors. A low number of pregnancy losses was also identified as a study limitation, but was consistent with other reports. And while 91% of the participants were taking a multivitamin, the composition of the multivitamins was unknown.

Overall, sufficient preconception 25-hydroxyvitamin D concentrations were associated with a significant increase in pregnancies and livebirths and a reduced rate of pregnancy loss after 8 weeks of gestation. While previous research has reported a limited ability to detect early pregnancy losses, this study highlights the importance of preconception health, specifically a sufficient vitamin D status, in achieving healthy pregnancy outcomes.

This study was supported by the National Institutes of Health and Doris Duke Charitable Foundation.

Reference

Mumford SL, Garbose RA, Kim K, et al. Association of preconception serum 25-hydroxyvitamin D concentrations with livebirth and pregnancy loss: a prospective cohort study [published online May 30, 2018]. Lancet Diabetes Endocrinol. doi: 10.1016/S2213-8587(18)30153-0

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