Westerdale, who was seven months pregnant, and her boyfriend were on the bus Aug. 30, heading to California. Her 4-year-old daughter was also on board.
The newborn's death brings the number of victims killed in the crash to nine.
Two children and one adult injured in the crash were still hospitalized Monday, according to Frank. He said one child is in critical condition. The other two are listed in satisfactory or stable condition.