What are other reason women bleed during pregnancy besides implantation? do those bleeding come heavy&cramping. how to tell difference from a period?

Implantation: Implantation bleeding is not really as common as the internet would have you believe. When it does happen it's usually 6-12 days after ovulation. A pregnancy test 7-10 days after unprotected intercourse is much more helpful. Implantation bleeding occurs exclusively in pregnant women. Infections, polyps, fibroids, hormonal imbalances and others are more common reasons for bleeding