Prenatal magnesium sulfate exposure and risk of cerebral palsy.

To the Editor. —The article by Dr Schendel and colleagues 1 may have more methodologic limitations than the authors acknowledge. Perhaps the major limitation is the failure to recognize that magnesium might be a marker for other phenomena that contribute to reduced risk of cerebral palsy. During the years study subjects were born (1986-1988), magnesium sulfate was not used as a first-line tocolytic. From 1984 through 1987,31% of the 90 women in one Boston, Mass, hospital who received magnesium sulfate just prior to the birth of a very low-birth-weight infant had a diagnosis of pregnancy-induced hypertension or preeclampsia recorded in the hospital chart, 2 similar to the experience in Atlanta, Ga reported by Schendel et al. 1 On interview, however, approximately 31% of these women acknowledged that they were told they had either preeclampsia or hypertension. If the situation in Atlanta mimicked what we found in Boston, then receipt of