Effects of 25OHD concentrations on chances of pregnancy and pregnancy outcomes: a cohort study in healthy Danish women

Abstract

Background/objectives: Plasma 25-hydroxyvitamin D (P-25OHD) concentrations may affect pregnancy outcomes. To elucidate this further, we studied the effects of pre-conception P-25OHD concentrations on chances for pregnancy as well as the effects of P-25OHD during pregnancy on the risk of miscarriage, birth weight and length, Apgar score and head circumference. Moreover, we studied whether pregnancy and breastfeeding patterns affect maternal P-25OHD concentrations.

Subjects/methods: A total of 153 healthy Caucasian women with pregnancy plans were followed with measurements performed before pregnancy, at pregnancy weeks 11±2, 22±1 and 35±2 as well as 15±7, 129±12 and 280±15 days postpartum. Furthermore, 75 non-pregnant, age-matched women were followed in parallel as controls.

Results: The 203 women were aged 29 (25-35) years. At baseline, median P-25OHD was 59 nmol/l. Of these women, 31% had P-25OHD <50 nmol/l, whereas 12% had levels above 80 nmol/l. Within ∼6 months after inclusion, 63% conceived. P-25OHD was not associated with chances of conceiving or overall risk of miscarriage. However, women with a miscarriage in their second trimester (n=3) had lower P-25OHD concentrations at measurements performed in the first trimester compared with women without a miscarriage (P=0.03). P-25OHD before or during pregnancy was not associated with gestational length or infant parameters. Adjustments for possible confounders did not change the result. During pregnancy, P-25OHD changed significant over time, but similar changes occurred within the control group, indicating no effect of pregnancy per se (P=0.59). Overall, P-25OHD did not differ according to length of breastfeeding at 2 weeks, and 4 and 9 months postpartum, although women breastfeeding for >9 months had lower P-25OHD levels at the last visit compared with the controls.

Conclusion: P-25OHD concentrations did not affect fertility or pregnancy outcomes, although low P-25OHD may be associated with an increased risk of late miscarriage.