Two U.S. senators are asking the federal government to address the growing problem of drug-dependent newborns, Reuters reports. They say thousands of infants are born each year to mothers who used opioids during pregnancy.

Senator Robert Casey of Pennsylvania called for hearings on why a federal law that directs states to protect drug-dependent newborns is not being enforced. Senator Charles Schumer of New York wants the Obama Administration to increase funding to help drug-dependent babies.

An investigation by Reuters found 110 babies and toddlers whose mothers used opioids during pregnancies and who died under preventable circumstances. In each case, the babies recovered enough to be discharged from the hospital, but were sent home to families not equipped to care for them.

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 study published earlier this year.

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 in 2004. That number jumped to 27 infants per 1,000 by 2013.

A federal law calls on states to safeguard these infants after they leave the hospital, but that effort is failing, Reuters notes.

Senator Schumer wrote a leader to the acting administrator of the Substance Abuse and Mental Health Services Administration, urging the agency to direct a portion of the $47 million allocated in the recent federal budget for drug abuse programs toward helping opioid-exposed babies.

“It’s become a sad fact that the latest victims of the prescription drug crisis in this country are the most vulnerable in our society, innocent babies,” Schumer said in a news release.

A spokesman for the Department of Health and Human Services told Reuters the senator’s request is being considered.