Effect of Vitamin D Supplementation on Unexplained Recurrent Spontaneous Abortion: A Double-Blind Randomized Controlled Trial.

BACKGROUND Recurrent spontaneous abortion is a serious problem in pregnancy, which affects between 2 and 5% of women of reproductive age. This study was designed to examine the effect of vitamin D supplementation on the occurrence of unexplained recurrent spontaneous abortion (URSA). METHODS A double-blind randomized and controlled clinical trial was performed on 80 patients with URSA. They were treated with vaginal progesterone (400 IU/day) after confirmation of pregnancy and received vitamin D and placebo in two intervention (n=40) and control groups (n=40), respectively. The incidence of abortion and the serum levels of IL-23 were examined within 20 weeks of gestation. RESULTS The levels of vitamin D3 prior to the start of the study were equal to 11.65±3.76 ng/ml and 11.53±2.39 ng/ml (p=0.86) in the intervention and control groups, respectively, which were decreased to 13.21±3.47 ng/ml and 11.08±2.76 ng/ml (p=0.004) at the end of the study, when the mean serum levels of IL-23 were equal to 18.4±3.78 pg/ml and 23.16±4.74 pg/ml in the two groups (p <0.004). The frequency of abortion in the control and intervention groups was equal to 5 (12.8%) and 13 (34.2%), respectively (p=0.03, OR=3.53, 95% CI= 1.12-11.2). CONCLUSIONS Vitamin D3 leads to decreased serum levels of IL-23 and incidence of abortion among women with URSA.