We recently reported on a late preterm infant born at 36 gestational weeks with serious arrhythmia due to hyperkalemia associated with long term maternal ritodrine administration. In a previous nation-wide surveillance, maternal combined administration of ritodrine and magnesium sulphate administration increased the risk of neonatal hyperkalemia in intermediate and late preterm infants born at 32–36 gestational weeks. It is unknown whether ritodrine alone increases the risk of neonatal hyperkalemia in late preterm infants born at 34–36 gestational weeks.
This single center retrospective cohort study enrolled late preterm infants born at 34–36 gestational weeks between 2004 and 2018. The association between neonatal hyperkalemia (K+> 6.0 mEq/l) during 72 hours of life and maternal ritodrine use were investigated. Cases with maternal magnesium sulphate were excluded.
In all, 213 late preterm infants with maternal ritodrine and 402 infants without tocolysis were included in the study. The risk of neonatal hyperkalemia was significantly increased by maternal ritodrine administration, with a crude odds ratio (OR) of 2.94 (95% confidence interval [CI] 1.20–7.61; p < 0.01) and an adjusted OR of 3.79 (95% CI 1.43–10.02; p < 0.01) on multivariable analysis. Long-term ritodrine administration (≥ 28 days) increased the risk of neonatal hyperkalemia.
This research suggests that late preterm infants born after long-term ritodrine administration are at risk of neonatal hyperkalemia and require special attention.