How does methadone affect unborn babies?

New Zealand babies born to mothers prescribed methadone during pregnancy lagged behind their peers, from motor skills and reflexes to the ability to settle, a new study shows.

For infants also exposed to other drugs, such as amphetamines – in addition to methadone -- during pregnancy, the negative effects persisted at two years of age.

Associate Professor Trecia Wouldes, of the University of Auckland, compared 86 babies born to mothers receiving methadone maintenance in Christchurch to 103 infants unexposed to methadone. Dr Wouldes and co-author Professor Lianne Woodward, of the University of Canterbury, drew on data from the Christchurch Methadone in Pregnancy (MIP) study.

Their research, just published in the journal PLOS One, is one of the few studies worldwide investigating the long-term effects of methadone on children. Opioids are the world’s biggest illicit drug problem, and methadone is the most commonly prescribed treatment for opioid dependence.

In the study, most of the babies were born with signs of drug withdrawal, with 88% requiring treatment with drugs such as morphine for their dependence. Overall, methadone-exposed infants showed poorer attention, suboptimal reflexes, poorer motor control, tighter muscles, and more fussing, crying and irritability, according to the study.

Within the group of 86 babies, the researchers identified a smaller group – 24 children in all – who fared the worst on early measures of neurobehaviour (such as reflexes, alertness, and motor development) and neurodevelopment (such as problem solving, language and motor development.)

Opioids are rated by the United Nations Office on Drugs and Crime as the illicit drug most harmful to health and well-being.

Compared to the rest of the methadone-exposed infants, these babies were more likely to be: male; exposed prenatally to more illegal drugs; born preterm; treated for drug withdrawal; and kept in hospital for longer after birth. At two years of age, they were lagging behind in cognition (language and problem solving) and motor development.

"To get a good start in life, children need to establish optimal patterns of sleep, feeding, and growth, and connection with parents,” said Dr Wouldes. "This research shows that for a small group of infants this may be more challenging. But if we can identify them early, we can try to ensure they get the support they need."

Opioids are rated by the United Nations Office on Drugs and Crime as the illicit drug most harmful to health and well-being. Increased abuse of opioid pain relievers in the U.S. and worldwide may mean more pregnant women are receiving methadone treatment for their dependence.

Methadone can help women dependent on opioids such as heroin to stabilize their lives by getting a substitute drug safely and legally.

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Paul Panckhurst | media adviser
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