Effect of Maternal Methadone Use on Neonatal Outcomes: Results of a Cohort Study

 Substance abuse treatment is challenging in pregnancy, and methadone maintenance therapy (MMT) is a therapeutic choice. Methadone can cross the placenta and is poorly secreted in breast milk. Given these inconsistent findings of methadone effect on neonatal outcomes, this study was done to investigate the results in neonates of mothers treated with methadone in Mashhad.

 In this retrospective cohort study, mothers referring to two academic hospitals of Mashhad University of Medical Sciences, Mashhad, Iran were studied. Three groups were considered: MMT, other drug abusers, and healthy control. Maternal information, including demographic characteristics, fertility characteristics, and methadone treatment-related characteristics, and neonatal information, including demographic characteristics and neonatal outcomes, were assessed.

 Overall, 122 pregnant women with a mean age of 29.14 ± 4.44 years were studied in three groups: control (n = 59), MMT (n = 32), and other drug abusers (n = 31). Baseline characteristics (mothers’ age, residence, chronic hypertension, preeclampsia, diabetes, heart disease, thyroid disease, and other diseases) were not different between the three groups. The highest history of miscarriage was seen in other drug abusers (35.5%) (P = 0.023). The mean weight, height, and head circumference of neonates in the control group were significantly higher than the MMT group (P < 0.001), and in the MMT group was higher than in the other drugs abusers (P < 0.001). The highest prevalence of malformations (16.1%) and hospitalization in the NICU (51.6%) was observed in infants of other drug abusers. After adjusting for confounding variables, the odds ratio (OR) of low-birth-weight infants was 13.7 in the MMT group and 1946 in the other drugs group compared to the healthy control group. The OR of neonates less than 50cm in height was 11.4 in the MMT group and 22.5 in the other drugs. Besides, the OR of neonates less than 35cm was 4.7 in the MMT group and 7.3 in other drugs.

 Although the neonates of mothers who used methadone had a higher rate of inappropriate intrauterine growth indices than control group, methadone consumption compared to other drugs had significantly reduced unacceptable outcomes in neonates. Increased gestational age and reduced preterm delivery risk were observed in methadone-treated mothers.