The number of babies treated for the drug-withdrawal syndrome known as neonatal abstinence syndrome (NAS) has almost quadrupled in the last decade, according to a new study.
Babies born with NAS undergo withdrawal from the addictive drugs their mothers took during pregnancy, such as oxycodone, morphine or hydrocodone.
NAS affected seven babies for every 1,000 admitted to a neonatal intensive care unit (NICU) in 2004.
That number jumped to 27 infants per 1,000 by 2013, HealthDay reports.
The percentage of days spent in a NICU because of drug withdrawal rose from 0.6 percent to 4 percent during that time, the researchers reported in The New England Journal of Medicine.
Eight centers reported that more than 20 percent of NICU days were spent caring for babies with the syndrome in 2013.
Another recent study found a woman's use of prescription opioids during pregnancy increases the risk her baby will be born small or early. Such use also raises the chance the baby will go through NAS.
The study of more than 112,000 pregnant women in Tennessee found almost 28 percent used at least one prescription opioid, such as hydrocodone or oxycodone. The risks to the baby increased if a woman also smoked or took antidepressants, the researchers reported.
Of the babies with NAS, 65 percent had mothers that legally filled prescriptions for opioid pain relievers.
The study found 42 percent of the women prescribed opioids smoked during pregnancy, compared with 26 percent of the women not prescribed opioids. The more cigarettes a woman smoked each day, the more likely she was to give birth to a baby with NAS.