Respiratory compromise after MgSO4 therapy for preterm labor in a woman with myotonic dystrophy: a case report

MgSO4 is widely used for tocolysis. Serious complications are rare as long as dosing is carefully monitored. Adverse effects in muotonic dustrophy have not been previously described.

A 35-year-old woman, gravida 1, para 0, was hospitalized with suspected mild myotonic dystrophy, polyhydramnios and preterm labor at 33 weeks. MgSO4 infusion rapidly resulted in respiratory compromise. Muscular strength returned to baseline after the infusion was stopped. Mother and infant proved to have myotonic dystrophy.

The choice of tocolytic medication in maternal myotonic dystrophy is problematic. Beta-2 sympathomimetics have been reported to precipitate myotonia. This case illustrates the potential for MgSO4 to cause respiratory embarrassment. Indomethacin may be the tocolytic of choice in myotonic dystrophy.