821 MAGNESIUM SULPHATE (MgSO4): FURTHER CONFUSION IN THE INTERPRETATION OF THE NEWBORN CBC

Abstract

MGSO4 is frequently used as a tocolytic agent and in the treatment of toxemia of pregnancy. Thus, MgSO4 is a common antenatal drug administered to the very low birth weight infant (VLBW i.e. <1500 gms). In a prospective study of non septic VLBW infants during the past 12 months mean corrected total white blood cell counts (WBC) during the first 24 hours of life were significantly depressed among infants exposed to MgSO4 in utero (N=42, mean gestational age=29 weeks, mean wt.=1082, mean 5′Apgar Score=7.0) in comparison to those whose mothers did not receive the drug. (N=45,mean gestational age=29.1 weeks, mean wt.=1070 gms,mean 5′Apgar Score=7.0). The mean corrected WBC were 9.3×103 vs 12.0×103 (p<.037). Total neutrophil (TNC) were found to be depressed in MgSO4 group in comparison to the non MgSO4 group with mean TNC 4166 vs 6008. More importantly, the incidence of leukopenia(WBC < 6000) was significantly higher in the MgSO4 treated group, 38% vs 13.3% (p < .05)but did not differ from that seen in a matched group of VLBW infants with blood culture proven sepsis, 38% vs 33%. These data lead us to conclude that MgSO4 administered to the mother may result in depression of the WBC and TNC in her infant. In the presence of MgSO4, leukopenia and neutropenia cannot be validly interpreted as evidence of infection in the newborn.