Objective: Determine whether infants exposed to chronic maternal methadone with abnormal intrapartum fetal heart rate (FHR) patterns are more likely to require treatment for neonatal abstinence syndrome (NAS).
Study design: Intrapartum FHR tracings analyzed in 104 pregnancies at ≥ 34 weeks gestation for FHR variability, accelerations, and decelerations. FHR patterns compared between neonates based on treatment with methadone for NAS. Secondary analysis included relation between maternal methadone dose and intrapartum FHR patterns, initiation of methadone, age at methadone initiation, and total neonatal methadone dose. Study powered to detect 30% increase in NAS incidence in neonates with abnormal FHR tracings.
Results: Seventy-six (73%) of 104 neonates required methadone treatment for NAS. Neonates who required methadone had higher average baseline FHR (131 vs. 126 bpm; p < 0.04) in active labor and less likely to have FHR tracings without accelerations (1.7% vs. 20.3%; p = 0.007) in latent labor. No significant associations between neonate's need for methadone and intrapartum FHR variability or FHR decelerations. No association between maternal methadone dose (range 30-280 mg) and treatment for NAS.
Conclusion: The need for an infant to require methadone treatment for NAS was not reliably predicted by the intrapartum FHR patterns or the maternal methadone dose.