A pregnant woman has been killed in a hit and run with her husband as they headed to a New York hospital, but their baby boy born prematurely has survived.

Authorities say Nachman Glauber and Raizy Glauber, both 21, were pronounced dead at hospitals after a BMW slammed into the car they were in early Sunday in Brooklyn's Williamsburg neighbourhood.

Police say their baby boy was delivered prematurely at hospital and the driver of their car was in a stable condition.

Isaac Abraham, a community leader in the Orthodox Jewish neighbourhood, had said the couple was going to the hospital for the child's birth, but he later said it wasn't clear why the Glaubers were headed there.