Prenatal vitamin D levels and postpartum hemorrhage in a rural Alaska cohort

To examine the relationship between prenatal vitamin D serum levels and postpartum bleeding.

We conducted a retrospective electronic health record cohort study of pregnant Alaska Native and American Indian (ANAI) people in southwestern Alaska who had at least one prenatal vitamin D level measurement recorded and had a vaginal birth between January 2017 and December 2019. Prenatal vitamin D level was the independent variable; postpartum abnormal bleeding and hemorrhage occurrence after a vaginal birth were the primary outcomes.

A total of 1343 index pregnancies were included in this study, of which 1258 (94%) had a vaginal birth with 370 (29%) experiencing blood loss ≥500 mL and 127 (10%) ≥1000 mL. Risk factors included prior postpartum hemorrhage, suspected macrosomia, twin gestation, magnesium sulfate use in the setting of pre-eclampsia, induction time >36 h, oxytocin use >12 h and third stage of labor >20 min. Deficient vitamin D levels (under 12 ng/mL) were found in 10.5%, 4.8%, and 5.3% of records in the first, second and third trimesters, respectively. Logistic regression indicated an association between vitamin D level under 12 ng/mL in the first trimester and postpartum bleeding ≥500 mL (n = 540, P = 0.0097, odds ratio [OR] = 2.2). No association was found between abnormal bleeding and being vitamin D deficient in the second and third trimesters.

There is a need for further research of vitamin D screening and supplementation before and during pregnancy as a possible risk reduction tool for abnormal postpartum bleeding.