Serum Magnesium Levels in Preterm Infants Are Higher Than Adult Levels: A Systematic Literature Review and Meta-Analysis.
BACKGROUND Antenatal magnesium sulfate can potentially reduce the risk of cerebral palsy in neonates delivered between 24 and 32 weeks of gestational age. Some studies using high-dose magnesium sulfate for neuroprotection have reported increased perinatal mortality. METHODS A retrospective study was conducted on 475 neonates born between 24 and 32 weeks of gestational age. Serum magnesium level in the first 24 h of life was used to stratify the neonates treated with antenatal magnesium into four subgroups: A (<2.5 mEq/L), B (≥2.5 to <3.5 mEq/L), C (≥3.5 to <4.5 mEq/L), and D (≥4.5 mEq/L). Primary outcome of survival without intraventricular hemorrhage (IVH) and/or periventricular leukomalacia (PVL) along with secondary outcomes, such as Apgar scores, resuscitation, intubation, broncho-pulmonary dysplasia, retinopathy of prematurity (ROP), patent ductus arteriosus (PDA), time to reach full feeds, length of stay (LOS), and mortality during immediate neonatal period were studied. RESULTS Of the 475 neonates included in the study, 289 (61%) received antenatal magnesium sulfate. Primary outcome of survival without IVH and/or PVL among the preterm neonates was 70.9% in those receiving and 74.2% in those not receiving antenatal magnesium (P=0.25). There were higher incidences of ROP (P=0.02), PDA (P=0.01), greater time to reach full feeds (P=0.03), and increased LOS (P=0.01) in neonates who had received antenatal magnesium. These findings were not statistically significant when the data were corrected for gestational age and birth weight. Among the subgroups, there was a significantly increased mortality rate (P<0.05) with increasing magnesium levels (5% vs. 16.9%, P<0.05 in groups A vs. D) and a trend toward higher intubation rate (P=0.1) and PDA (P=0.14). CONCLUSION Antenatal magnesium is safe in the immediate postnatal period; however, in the subset of preterm neonates with serum magnesium levels >4.5 mEq/L, there is increased mortality independent of birth weight and gestational age. Identification of these neonates and appropriate dosing for their antenatal neuroprotection needs to be studied.