A 34-year-old nulliparous gravid female presented with acute bilateral pyelonephritis at 29 + 5 weeks gestation. The patient was relatively well until two weeks ago when a slight increase in amniotic fluid was noted. Further investigation revealed myoglobinuria and significantly elevated levels of creatine phosphokinase. The patient was subsequently diagnosed with rhabdomyolysis. Twelve hours after admission, the patient noted reduced fetal movements. A non-stress test revealed fetal bradycardia and non-reassuring variability in fetal heart rate. An emergency cesarean section was performed, and a “floppy” female child was delivered. Genetic testing revealed congenital myotonic dystrophy, and the mother was also diagnosed with myotonic dystrophy. Rhabdomyolysis has a very low incidence in pregnancy. Herein, we report a rare case of myotonic dystrophy with rhabdomyolysis in a gravid female with no history of myotonic dystrophy. Acute pyelonephritis is a causative agent of rhabdomyolysis that results in preterm birth.