The effects of methadone treatment on the reactivity of the nonstress test

Abstract

The effect of methadone treatment on the nonstress test (NST) was studied. Thirty narcotic-addicted gravidas on methadone maintenance underwent NSTs, performed and interpreted in a standard manner, before and 1 hour after taking the usual methadone dose. Urines were screened for commonly abused substances on the day of testing. Mean gestation when tested was 34 weeks and mean methadone dose was 26 mg/day. All urines were positive for methadone, six for cocaine, two for opiates, and one for amphetamines. The reactivity of the NSTs performed 1 hour after methadone ingestion was decreased significantly compared with that of tests performed before medication (P less than .04). Decreases in the frequencies of fetal movements and fetal heart rate accelerations were significant (P less than .001 and P less than .01, respectively). These results suggest that methadone treatment altered the morphology of the NST, which may limit the reliability of this test for determining fetal well-being in these high-risk gravidas if time of medication is not taken into consideration.