Perinatal death and tocolytic magnesium sulfate

Objective: To determine whether there is a significant association between perinatal mortality and exposure to total doses of tocolytic magnesium sulf ate larger than 48 g. Methods: We did a case-control study in which cases were defined as neonate s or fetuses who died after being exposed to tocolytic magnesium sulfate an d controls were those who survived exposure. The study included fetuses and neonates who weighed between 700 and 1249 g and whose mothers had received tocolytic magnesium sulfate at Chicago Lying-in Hospital between January 1 , 1986, and March 31, 1999. We excluded women who received prophylactic mag nesium sulfate for preeclampsia or preeclampsia superimposed on chronic hyp ertension, and fetuses or neonates with major congenital anomalies. Data we re analyzed by Fisher exact test, chi(2) Lest, Student t test, Mann-Whitney U test, multivariable logistic regression, and Cochrane-Armitage trend tes t. Results: Controlling for birth weight or gestational age, year of delivery, receipt of betamethasone, acute maternal disease, and maternal race in a m ultivariable model, we found that exposure to total doses of tocolytic magn esium sulfate exceeding 48 g was significantly associated with increased pe rinatal mortality (adjusted odds ratio 4.7; 95% confidence interval 1.1, 20 .0; P = .035). Using the Cochrane-Armitage trend test, we found that a sign ificant dose response was present (P = .03), but one that was most consiste nt with a threshold effect. Conclusion: Our findings support the hypothesis that high doses of tocolyti c magnesium sulfate are associated with increased perinatal mortality among fetuses and neonates weighing 700-1249 g. (C) 2000 by The American College of Obstetricians and Gynecologists.