Magnesium tocolysis and neonatal bone abnormalities: a controlled study.

This study was conducted to investigate the relationship between maternal administration of intravenous (IV) magnesium sulfate and radiographic abnormality of neonatal long bones. Eleven neonates in the exposed group were born to mothers who had received IV magnesium tocolysis for more than 7 days. Two gestational age-matched unexposed neonates were selected for each member of the exposed group. Initial chest radiographs of exposed and unexposed neonates were reviewed in random sequence by a pediatric radiologist who was blinded to exposure status. On evaluation of the proximal humeri, six neonates had radiographic abnormalities consisting of transverse radiolucent and/or sclerotic bands; all six were in the exposed group. The difference in radiographic findings between the exposed and unexposed groups was statistically significant (P less than .001). These results support the existence of a causal relationship between prolonged IV magnesium tocolysis and abnormal fetal bone mineralization. Further study is needed to elucidate the mechanism and clinical significance of these bone changes.