Background: Vitamin D insufficiency and deficiency can be associated with adverse effects
on pregnancy outcomes, which may include recurrent pregnancy loss through the mechanisms
that are yet unknown. The aim of this study was to evaluate the effect of 1,25VitD3 on regulatory
T cells (Tregs) and T helper17 (Th17) cell populations In vitro in unexplained recurrent pregnancy
loss (URPL) patients and healthy women.
Methods: Samples from 20 non-pregnant women with a history of URPL were compared to 20 normal
non-pregnant women. Peripheral blood mononuclear cells (PBMC) were divided into 3 wells
for each subject: in the presence of 1, 25 VitD3 (50 nM, for 16 hours), PHA (positive control)
(10μM), and without any treatment (as a baseline or negative control). The percentage of regulatory
T cells and Th17 cells was measured by flow cytometry at baseline and then after cell culture experiments.
Results: Our study indicated that the percentage of Tregs in patients with URPL was significantly
lower than the control group (2.42 ± 0.27 vs. 3.41 ± 0.29, P= 0.01). The percentage of Th17 cells
was significantly greater in URPL patients compared to the control group (2.91 ± 0.33 vs. 1.18±
0.15, P=0.001). 1, 25VitD3 treatment significantly increased the percentage of Tregs from the baseline
in the URPL group compared to that in the control group (1.23 ± 0.03 vs. 1.00 ± 0.03, P=
Conclusion: Vitamin D deficiency may be a contributor to recurrent pregnancy loss and suggests
supplementation of women with Vit D pre-pregnancy may be protective against URPL.