This retrospective cohort study examined whether the timing of maternal magnesium sulfate (MgSO₄) discontinuation before delivery affects the risk of apnea of prematurity (AOP) in 322 late-preterm twin infants (34 0/7–36 6/7 weeks) born at a single Japanese center from 2017–2025.
AOP occurred in 112/322 infants (34.8%). Delivery within 12 h of MgSO₄ cessation was independently associated with AOP (aOR 7.44; 95% CI 1.48–37.4), while discontinuation intervals of 12–24 h or ≥24 h were not. MgSO₄ exposure alone (without timing) was not significantly associated with AOP.
Single-center retrospective design limits generalizability; study is restricted to twin pregnancies, so findings may not apply to singletons; the <12 h subgroup likely had a small sample size, widening the confidence interval and raising precision concerns.
When MgSO₄ is used in late-preterm twin pregnancies, clinicians should consider the interval between drug cessation and delivery when planning neonatal respiratory monitoring — delivery within 12 h of stopping MgSO₄ carries a markedly elevated AOP risk. This timing factor may be worth incorporating into perinatal handoff communications.
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