Skeletal demineralization and fractures caused by fetal magnesium toxicity.

Two surviving female infants, born from a triplet pregnancy at 30 weeks gestation, were noted to have severe osteopenia and multiple fractures diagnosed at 20 days of age. Their mother had been treated for preterm labor with intravenous magnesium sulfate from week 22 until their birth at 30 weeks gestation. At birth, the triplets exhibited craniotabes with enlarged fontanelles and sutures. All developed Respiratory Distress Syndrome (RDS) and the two surviving infants required prolonged respiratory support. Serum calcium and phosphate levels were normal and alkaline phosphatase levels were increased. The infants were treated with supplements of calcium and phosphorous, with resultant healing of the multiple fractures without deformity. Fetal magnesium toxicity impairs bone mineralization and can lead to serious bone demineralization that may cause fractures in the newborn period that complicate recovery from respiratory disease. Early recognition and treatment may minimize complications related to osteopenia caused by fetal magnesium toxicity.