RR, Charru A, et al. Molecular basis of human hypertension: Role of angiotensinogen. Cell 1992;71:169 – 80. 3. Bernstein IM, Ziegler W, Stirewalt W, Brumsted J, Ward K. Angiotensinogen genotype and plasma volume in nulligravid women. Obstet Gynecol in press, 1998. 4. Soffronoff EC, Kaufmann BM, Connaughton JF. Intravascular vol- ume determinations and fetal outcomes in hypertensive diseases of pregnancy. Am J Obstet Gynecol 1977;127:4 –9. 5. Gallery EDM, Hunyor SN, Gyory AZ. Plasma volume contraction: A significant factor in both pregnancy associated hypertension (pre-eclampsia) and chronic hypertension in pregnancy. QJM 1979;48:593– 602. 6. Schobel HP, Fischer T, Heuszer K, Geiger H, Schmeider RE. Preeclampsia—A state of sympathetic overactivity. N Engl J Med 1996;335:1480 –5. 7. Clapp JF, Capeless EL. Cardiovascular function before, during, and after the first and subsequent pregnancies. Am J Cardiol 1997;80:1469 –73. 8. Koller A, Sun D, Kaley G. Role of shear stress and endothelial prostaglandins in flow and viscosity induced dilation of arterioles in vitro. Circ Res 1993;72:1276 – 84. 9. MacGillivray I, Rose GA, Rowe D. Blood pressure survey in pregnancy. Clin Sci 1969;37:395– 407. 10. Hubel CA, Roberts JM, Taylor RN, Musci TJ, Rogers GM, McLaughlin MK. Lipid peroxidation in pregnancy: New perspec- tives on preeclampsia. Am J Obstet Gynecol 1989;161:1025–34. 11. Easterling TR, Benedetti TJ, Schmucker BC, Millard SP. Maternal hemodynamics in normal and preeclamptic pregnancies: A longi- tudinal study. Obstet Gynecol 1990;76:1061–9. 12. National high blood pressure education program working group report on high blood pressure in pregnancy. Am J Obstet Gynecol 1990;163:1689 –1712. 13. van Selm M, Kanhai HH, Gravenhorst JB. Maternal hydrops syndrome: A review. Obstet Gynecol Surv 1991;46:785– 8. 14. French W, Freund U, Carlson RW, Weil MH. High output heart failure associated with pulmonary edema complicating hydatidi- form mole. Arch Intern Med 1977;137:367–9. Address reprint requests to: Ira M. Bernstein, MD Department of Obstetrics and Gynecology Shepardson 331, FAHC 111 Colchester Avenue Burlington, VT 05401-1435 E-mail: ibernste@zoo.uvm.edu Received January 30, 1998. Received in revised form March 27, 1998. Accepted April 10, 1998. Copyright © 1998 by The American College of Obstetricians and Gynecologists. Published by Elsevier Science Inc. If tocolytic magnesium sulfate is associated with excess total pediatric mortality, what is its impact? Robert Mittendorf, MD, DrPH, Peter Pryde, MD, Babak Khoshnood, MD, and Kwang-Sun Lee, MD The Magnesium and Neurologic Endpoints Trial was a randomized controlled trial (RCT) done to learn whether or not receiving magnesium sulfate during preterm labor could prevent cerebral palsy. Unexpectedly, in the tocolytic arms of the trial, seven (including one set of twins) of 46 cases assigned to receive magnesium ended in total pediatric mortality (fetal  neonatal  postneonatal), compared to none of 47 cases assigned to other tocolytics ending in death. The difference between the two treatment arms is highly statistically significant (risk difference 15.2%; 95% confi- dence interval 4.8, 25.6; P  .006). If this relationship is confirmed by experimentation with animals or through the conduct of a large RCT at other institutions, it is possible that tocolytic magnesium will be found to be associated with the deaths of several thousand newborns in the United States annually. If the true excess total pediatric mortality is 10%, and if magnesium accounts for 40% of all tocolytics used, then tocolytic magnesium increases the absolute num- ber of infant deaths by about 4800 every year. (Obstet Gynecol 1998;92:308 –11. © 1998 by The American College of Obstetricians and Gynecologists.) Recently, we reported an unanticipated excess of total pediatric mortality (fetal + neonatal + postnatal) in pregnancies exposed to magnesium under circum- stances unrelated to preeclampsia. 1 Because magne- sium ranks among the most popular tocolytics in the United States, this observation is alarming and warrants attention while additional data are gathered to confirm the putative association, assess causality, and evaluate the clinical impact of magnesium-related fetal toxicity, if it exists. The purpose of this commentary is fourfold: 1) to alert the obstetric community to the statistically significant association between tocolytic magnesium and total pediatric death observed in a randomized controlled trial (RCT), 2) to evaluate our findings in the context of the previously reported data, evaluating the From the Department of Obstetrics and Gynecology, Section of Neonatology, Department of Pediatrics, Pritzker School of Medicine, and the Irving B. Harris Graduate School of Public Policy Studies, Univer- sity of Chicago, Chicago, Illinois 308 0029-7844/98/$19.00 Obstetrics & Gynecology PII S0029-7844(98)00163-X