The Association Between Maternal Vitamin D Deficiency and Postpartum Hemorrhage and Uterine Atony

( Acta Obstet Gynecol Scand. 2024;103:286–293. DOI: 10.1111/aogs.14719) Postpartum hemorrhage (PPH) is the leading cause of maternal mortality and morbidity globally, causing about 140,000 deaths per year. PPH can be attributed to 4 primary causes: tone, trauma, tissue, and thrombin. The most common cause is an atonic uterus (70% of cases), followed by trauma (20%), tissue (10%), and thrombin (1%). Hemostasis after delivery primarily relies on uterine myometrium contraction, which compresses the large vessels in the placental bed. Vitamin D deficiency, prevalent globally and in Sweden (25% to 60%), varies with diet, season, and supplementation. It is measured by serum 25-hydroxylated vitamin D (25 OHD) levels, with insufficiency defined as <50 nmol/L and deficiency as <25 nmol/L.