Why was the RX given for Morning Sickness in late discontinued?

The RX you are referring to is likely Diclegis, a combination of doxylamine and pyridoxine (vitamin B6) that was used to treat morning sickness. It was discontinued in the late 2010s due to safety concerns. Specifically, there were concerns that the doxylamine component could increase the risk of birth defects if taken during the first trimester of pregnancy. As such, the manufacturer of Diclegis voluntarily recalled the product to ensure the safety of pregnant patients.