I had red bleeding at 19 weeks, i went to the er & babys ultrasound was normal & cervix was closed. doctor checked the cervix & didnt see anymore bleeding, the bleeding stopped right afterwards. could the cause be birth defect?

Unlikely: Birth defects in the baby won't cause vaginal bleeding, there are several causes for bleeding during the second trimester,the most important thing done at the ER is that they made made sure pregnancy is intact and cervix is closed, please see your OB soon for evaluation and continue the prenatal care, wish you a healthy pregnancy and a healthy baby