Heart-wrenching cries echo through the halls of the neonatal intensive care unit at East Tennessee Children's Hospital. Nearly half of the newborn babies in the hospital's NICU are suffering from prescription drug withdrawal.

For over a year, the Knoxville hospital has been dealing with a dramatic increase in the number of newborns with neonatal abstinence syndrome, or NAS, which is the withdrawal process a newborn baby goes through after in utero exposure to certain medications.

"When I first got into neonatology the most common problem -- and still the most common problem -- that we take care of is premature babies or babies with respiratory distress," said neonatology director Dr. John Buchheit, a 17-year veteran at Children's. "But I had no idea that we would be seeing this issue, to this degree."

Narcotics used during pregnancy pass through the placenta to the baby. Once the baby is born, he or she no longer has access to the drugs and will likely go through withdrawal. According to Buchheit, opioids -- like oxycodone -- are the worst offenders for the babies suffering from NAS at his hospital.

Between 55% and 94% of babies exposed to opioids prior to birth exhibit signs of withdrawal, according to the American Academy of Pediatrics.