Association of serum vitamin D level and the miscarriage rate in women presenting with threatened miscarriage to the Early Pregnancy Assessment Clinic

Research question Is low serum 25-hydroxyvitamin D (25(OH)D) associated with an increased risk of miscarriage in women who presented with threatened miscarriage to the Early Pregnancy Assessment Clinic (EPAC)? Design This is a secondary retrospective analysis using archived serum samples from a randomised, double-blind, placebo-controlled trial. Stored serum samples of 371 women presenting with threatened miscarriage during the first trimester in the EPAC were assayed for 25(OH)D by liquid chromatography-mass spectrometry. Results The overall miscarriage rate was 45/371 (12.1%) in the whole cohort. Grouping vitamin D insufficiency and vitamin D sufficiency together into the “non-deficient” group and excluding those who underwent termination of pregnancy, there was no difference in the miscarriage rate between those who were vitamin D deficient compared to those who were vitamin D non-deficient [25/205, 12.2% vs 20/157, 12.7%, p=0.877, OR 0.951, 95% CI 0.507-1.784]. When analyzed according to their gestational weeks, the miscarriage rate was significantly higher in the vitamin D non-deficient group compared with the vitamin D deficient group in women who presented at gestational 6 weeks or earlier [10/58 (17.2%) vs 13/33 (39.4%), p= 0.019], but there was no statistically significant differences between the two groups at other gestation. There was no difference in the vitamin D levels in women who had a miscarriage compared to those who had a livebirth [48 (37-57) vs 47 (37-58) nmol/L, p=0.725]. Conclusions Low serum vitamin D level was not associated with an increased risk of miscarriage in women with threatened miscarriage presenting to the EPAC.