Methadone and perinatal outcomes: a prospective cohort study.

Aims:   Methadone use in pregnancy has been associated with adverse perinatal outcomes and neonatal abstinence syndrome (NAS). This study aimed to examine perinatal outcomes and NAS in relation to (i) concomitant drug use and (ii) methadone dose.

Design:   Prospective cohort study.

Setting:   Two tertiary care maternity hospitals.

Participants:   A total of 117 pregnant women on methadone maintenance treatment recruited between July 2009 and July 2010.

Measurements:   Information on concomitant drug use was recorded with the Addiction Severity Index. Perinatal outcomes included pre-term birth (<37 weeks' gestation), small-for-gestational-age (<10th centile) and neonatal unit admission. NAS outcomes included: incidence of medically treated NAS, peak Finnegan score, cumulative dose of NAS treatment and duration of hospitalization.

Findings:   Of the 114 liveborn infants 11 (9.6%) were born pre-term, 49 (42.9%) were small-for-gestational-age, 56 (49.1%) had a neonatal unit admission and 29 (25.4%) were treated medically for NAS. Neonates exposed to methadone-only had a shorter hospitalization than those exposed to methadone and concomitant drugs (median 5.0 days versus 6.0 days, P = 0.03). Neonates exposed to methadone doses ≥80 mg required higher cumulative doses of morphine treatment for NAS (median 13.2 mg versus 19.3 mg, P = 0.03). The incidence and duration of NAS did not differ between the two dosage groups.

Conclusions:   The incidence and duration of the neonatal abstinence syndrome is not associated with maternal methadone dose, but maternal opiate, benzodiazepine or cocaine use is associated with longer neonatal hospitalization.