In recent years, interest in the evaluation of vitamin D levels and the possible outcomes of their deficiency during pregnancy has increased. However, there is no consensus on when to start vitamin D supplementation, its duration, dosage, and the optimum level during pregnancy. The toxicity of vitamin D is as important as its deficiency. From the history of a 5-day-old male baby who was investigated for hypercalcemia, it was learned that the mother took 300,000 IU vitamin D-five ampoules/oral at 30 weeks of gestation every other day. The infant was born prematurely, postpartum bradycardia required positive pressure ventilation, and his hypercalcemia lasted approximately 4 months despite treatment. Maternal excessive and inappropriate use of vitamin D can cause preterm labor and severe hypercalcemia, which is a life-threatening complication in the neonatal period. This case is presented to draw attention to the negative effects of maternal high-dose vitamin D during pregnancy.
Keywords: 25 (OH) vitamin D; Hypercalcemia; neonatal outcomes; vitamin D intoxication.