Umbilical Cord Magnesium Levels and Neonatal Resuscitation in Infants Antenatally Exposed to Magnesium Sulfate
Abstract Number: T-39
Abstract Type: Original Research
Introduction: Antenatal magnesium sulfate (MgSO4) administration has been associated with neonatal morbidity including poor tone and low Apgars, both surrogates for neonatal respiratory depression.(1-2) We previously determined MgSO4 pharmacokinetics (PK) and placental transfer, but the neonatal pharmacodynamics (PD) effects related to PK are unknown.(3) The aim of this study was to characterize the association between umbilical cord magnesium levels and the need for neonatal resuscitation in a cohort of neonates exposed to MgSO4 for either neuroprotection or preeclampsia.
Methods: Secondary neonatal pharmacodynamics analysis following a prospective, IRB-approved study of pregnant women prescribed MgSO4 for preeclampsia or prematurity (< 32 wks gestation) to determine maternal pharmacokinetics and pharmacodynamics after MgSO4 administration (3). Women received a 4g loading dose and a 2g/hr maintenance dose of MgSO4. Univariate and multivariate techniques were used to examine the impact of umbilical cord blood magnesium levels and the need for neonatal resuscitation (oxygen, bag/mask ventilation, intubation, or chest compressions), controlling for gestational age, mode of anesthesia, indication for magnesium sulfate, total dose of magnesium sulfate, and infant sex. A p-value of <0.05 was considered statistically significant.
Results: 55 umbilical cord magnesium samples were collected. Umbilical cord blood magnesium levels were highly correlated with total dose of MgSO4 exposure (r=724; p=0.01), however, these variables did not significantly predict neonatal respiratory outcomes. Delivery at a later gestational age was the only independent protective factor against need for neonatal resuscitation in the final regression model (OR = 0.6 (0.5, 0.9); p= 0.006). (Table)
Conclusion: Although magnesium exposure has been implicated as a predictor of the need for neonatal resuscitation after birth, this data suggests those outcomes are primarily driven by the gestational age of the infant and not the absolute amount of MgSO4 exposure or placental transfer antenatally.
1) AJOG 2015; 212: 94.e1–94.e7
2) Am J Perinatol 2012; 29: 795–799
3) Society for Obstetric Anesthesia and Perinatology Annual Scientific Meeting 2014