ABSTRACT
Prolonged infusion of magnesium sulfate has been used for the treatment of refractory
preterm labor. Long-term magnesium sulfate tocolytic therapy either alone or in combination
with other tocolytic agents has been reported to be safe and effective with minimal
maternal side effects. There has been only one previous report of a disturbance in
maternal calcium homeostasis, which included decreased distal radius bone density
and hypercalciuria as a result of prolonged magnesium sulfate infusion. This article
reports the first case of bilateral fracture of the calcanei in the postpartum period
secondary to osteoporosis associated with prolonged magnesium sulfate tocolysis and
bed rest. A 35-year-old white female with a triplet pregnancy of 25 weeks' gestation
was admitted in preterm labor. Bed rest, intravenous magnesium sulfate to-colysis,
and intermittent subcutaneous terbutaline were necessary to maintain uterine quiescence
for 65 days. The patient received weekly betamethasone for 6 weeks for the acceleration
of fetal lung maturation. Daily prenatal multivitamins and low-dose subcutaneous heparin
for thromboprophylaxis were given. Efforts at tocolysis were ultimately not successful
and the patient underwent a cesarean section delivery at 34 2/7 weeks' gestation.
The patient's postoperative course was complicated by osteoporosis and bilateral stress
fractures of the calcanei. This case report demonstrates that stress fractures secondary
to osteoporosis may be associated with prolonged magnesium sulfate therapy and bed
rest in higher order multiple pregnancy. Other possible contributing factors to osteoporosis
include heparin thromboprophylaxis and suboptimal calcium supplementation. Therefore,
in circumstances of prolonged bed rest and magnesium sulfate tocolysis, additional
daily calcium supplementation would be well advised.
Keywords
Magnesium sulfate - osteoporosis - pregnancy - tocolysis
