Maternal methadone use in pregnancy: factors associated with the development of neonatal abstinence syndrome and implications for healthcare resources.

OBJECTIVES: The objectives of this study were to investigate factors associated with the development of neonatal abstinence syndrome (NAS) and to assess the implications for healthcare resources of infants born to drug-misusing women.

DESIGN: Retrospective cohort study from 1 January 2004 to 31 December 2006.

SETTING: Inner-city maternity hospital providing dedicated multidisciplinary care to drug-misusing women.

POPULATION: Four hundred and fifty singleton pregnancies of drug-misusing women prescribed substitute methadone in pregnancy.

METHODS: Case note review.

MAIN OUTCOME MEASURES: Development of NAS and duration of infant hospital stay.

RESULTS: 45.5% of infants developed NAS requiring pharmacological treatment. The odds ratio of the infant developing NAS was independently related to prescribed maternal methadone dose rather than associated polydrug misuse. Breastfeeding was associated with reduced odds of requiring treatment for NAS (OR 0.55, 95% CI 0.34-0.88). Preterm birth did not influence the odds of the infant receiving treatment for NAS. 48.4% infants were admitted to the neonatal unit (NNU) 40% of these primarily for treatment of NAS. The median total hospital stay for all infants was 10 days (interquartile range 7-17 days). Infants born to methadone-prescribed drug-misusing mothers represented 2.9% of hospital births, but used 18.2% of NNU cot days.

CONCLUSIONS: Higher maternal methadone dose is associated with a higher incidence of NAS. Pregnant drug-misusing women should be encouraged and supported to breastfeed. Their infants are extremely vulnerable and draw heavily on healthcare resources.