Rh Factor

Rh factor is a blood protein that plays a critical role in some pregnancies. People without Rh factor are known as Rh negative, while people with the Rh factor are Rh positive. If a woman who is Rh negative is pregnant with a fetus who is Rh positive, her body will make antibodies against the fetus's blood. This can cause Rh disease, also known as hemolytic disease of the newborn, in the baby. In severe cases, Rh disease leads to brain damage and even death. Since 1968, a vaccine has existed to prevent the mother's body from making anti-bodies against the fetus's blood.