ASSESSMENT OF FETAL WELL-BEING IN METHADONE-MAINTAINED PREGNANCIES - ABNORMAL NONSTRESS TESTS

Objective: To investigate parameters of fetal well-being (characterist ics of nonstress test, NST, and antepartum fetal heart rate, FHR, patt erns) and selected neonatal outcomes in pregnant women on methadone ma intenance. Study Design: A matched case-control study of methadone-tre ated women receiving prenatal and intrapartum care at a Bronx municipa l hospital during 1992-1994. 102 NSTs obtained from 24 methadone-treat ed women after 35 weeks of pregnancy were compared to 96 NSTs from a c ontrol group (n = 24), matched for maternal age, parity, and gestation al age. All NSTs were evaluated for general characteristics including time interval between initiation and achievement of reactive NST (2 ac celerations greater than or equal to 15 bpm lasting for at least 15 s in a 20-min period), baseline, amplitude of fluctuation, frequency of fluctuation, accelerations and decelerations. The scoring system descr ibed by Lyons et al. was used for all NSTs. All nonreactive NSTs were followed with biophysical profile tests. Results: The frequency of non reactive NSTs was significantly higher for methadone-maintained women compared to controls (19.6 vs. 4.2%; p < 0.01). The average length of time to achieve reactive NST was significantly (p = 0.0016) longer for the methadone-treated group when compared to controls (35.50 +/- 20.9 6 vs. 14.85 +/- 9.03 min). The total score (Lyons et al.) was signific antly lower (p < 0.0007) for the methadone-treated group compared to c ontrols. Mean birth weight, Apgar scores at 1 and 5 min, meconium, and umbilical cord artery pH were not significantly different for methado ne-exposed neonates compared to controls. Conclusion: Methadone-mainta ined pregnancies are significantly associated with a higher incidence of nonreactive NSTs, longer intervals to achieve reactive NSTs and low er NST scores compared to controls. This may reflect an altered respon se in fetal central nervous system neurotransmitters and changes in fe tal behavior induced by methadone.