What is rh incompatibility?

Pregnancy risk: The presence or absence of the Rh factor is what makes our blood type either positive or negative. Rh incompatibility occurs when a woman with a negative blood type carries a fetus with a positive blood type. When fetal cells enter the maternal circulation, her immune system can form antibodies to the Rh antigen that can attack the fetal cells in a subsequent pregnancy. Rhogam helps lower risk.

Kinda complicated!: We all have a blood type such as a, b, ab, or o but also are either Rh negative or Rh positive. Rh incompatibility is when the mom is Rh negative and the baby is Rh positive. In this case, the mom can form antibodies which cross the placenta and hurt the fetal red blood cells, making the baby anemic. We counter this by giving Rh negative moms an injection called Rhogam to stop antibody formation.