A new study says the number of babies born in the United States addicted to drugs taken by their mother has nearly tripled in less than a decade.
According to the study in the Journal of the American Medical Association, about 13,500 babies were born with withdrawal symptoms in 2009 - roughly one every hour.
The report says abuse of prescription painkillers is partly to blame. The number of mothers using opiates has increased five-fold and doctors are being criticised for prescribing painkillers too easily to patients who demand them.
The study says in addition to seizures and breathing problems, the addicted babies suffer from a low birth weight, irritability, muscle cramping, tremors, feeding problems and vomiting.
The study, the first of its kind in the US, was based on records from more than 4000 hospitals across the country, the BBC reports.
Not all babies born to women who used opiates during pregnancy showed the symptoms, the report said. However, those that did often required treatment with the opiate-replacement drug methadone to help wean them off their dependency.
The babies were kept in hospital for an average of 16 days, compared to three for healthy infants.
The researchers said many pregnant women were legitimately taking pain-relieving opiates on prescription, but warned that more must be done to find ways of protecting unborn babies from powerful drugs.
Call to ask NZ women about drug use
In New Zealand, a researcher is urging health workers to ensure they ask pregnant women if they use drugs and which ones.
Trish Wouldes works in the department of psychological medicine at Auckland University and says there is growing drug use by women in New Zealand but there has been no equivalent study to the American one of the effects on babies.
Dr Wouldes says pregnant women may be using opiates, marijuana, methamphetamine, alcohol and tobacco, but they are not usually asked about it.