This is what happens when an addict has a baby 😭 What is Neonatal Abstinence Syndrome? Neonatal Abstinence Syndrome (also called NAS) is a group of conditions caused when a baby withdraws from certain drugs he’s exposed to in the womb before birth. NAS is most often caused when a woman takes drugs called opioids during pregnancy. But it can also be caused by antidepressants (used to treat depression), barbiturates or benzodiazepines (sleeping pills). When you take these drugs during pregnancy,