Rh sensitization is a complication of pregnancy where a woman can make antibodies against her own baby causing that baby to become sick even while still in the uterus. This occurs when a woman with an Rh negative blood type (A Negative, B negative, AB negative or O negative) conceives a child with a father who has an Rh positive blood type. If the baby turns out to be Rh positive like the father, then the mother’s body makes antibodies against the baby’s red blood cells. The red blood cells can be destroyed making the baby anemic. In a fetus, this can cause a serious condition called hydrops fetalis which can be so severe that the baby dies.
Because the immune system has a "memory" each time a woman is exposed to an Rh positive baby her response gets bigger and more aggressive.
The Rh "factor" is actually a protein that sticks out on the surface of the red blood cells. The instructions for how to make a particular protein are found in the genes.
This problem isn’t as common as it used to be. The reason is due to the use of a medication called Rhogam. Rh negative mothers who are given the Rhogam injection during and after a pregnancy with an Rh positive baby will be prevented from making the antibodies so that subsequent pregnancies won’t be affected.
However, cases of Rh sensitization still occur.
A recently published case report describes the use of preimplantation genetic diagnosis – PGD to detect embryos that are Rh negative. These Rh negative embryos are placed into the uterus during embryo transfer. By avoiding the Rh positive embryos, the mother will not make antibodies against the baby thereby completely eliminating the problem!
This is a novel and fantastic way use preimplantation genetic diagnosis – PGD. There are some limitations to its use however. For example, the fathers who are Rh positive must have at least one copy of a gene that does not make the Rh factor. (some will have two copies of the gene that makes the Rh factor).