If you are planning to become pregnant, it’s a good idea to talk to your doctor about a blood test to determine your Rh factor. This is a good move for both yourself and your partner. While very rare, complications related to Rh factor can be serious, so it doesn’t hurt to get as informed as possible about your risks.
So: what is Rh factor?
Rhesus (Rh) factor refers to whether or not your red blood cells have a certain protein. If they do, you are Rh positive, and if they don’t, you are Rh negative. Two Rh positive parents will have an Rh positive child, while two Rh negative parents will have an Rh negative child. About 85% of people are Rh positive [1].
It’s not “better” or “worse” to be one or the other, but pregnancy complications can occur when the mother is Rh negative and the father is Rh positive, because the baby may be Rh positive like his father [1].
Why is that a problem?
Mama and baby have separate circulatory systems, so their blood is unlikely to mix except during childbirth or with certain tests or complications/trauma in utero. However, if an Rh negative mama is exposed to her Rh positive baby’s blood, mama’s immune system interprets that Rh positive blood as a threat. As is the function of our immune systems, hers will try to destroy the threat. This, of course, is dangerous to baby [1].
How does Rh factor affect second pregnancies and beyond?
If your first baby is Rh negative, there is no danger. However, if your first baby is Rh positive while you are negative, it’s very possible his blood has mixed with yours during childbirth, whether vaginal or C-section. (This is also true if your first pregnancy was ectopic or if you had a miscarriage or termination.) In response, your body has produced antibodies to Rh positive protein. The next time you are pregnant, an Rh positive baby is vulnerable to your antibodies [1].
What actions should I take if I am Rh negative?
Again, if your partner is also Rh negative, there is no issue. Your doctor will prescribe an antibody screen to check whether your blood has already produced antibodies to the Rh positive protein. If not, at around 28 weeks of pregnancy, you will be given a dose of RhIg (Rh immunoglobulin) to prevent those antibodies from forming. It will be administered again within 72 hours after birth [1].
What if I do have antibodies?
If you have antibodies, RhIg will not help. In this case, your doctor will watch your pregnancy carefully and test baby for signs of anemia or hemolytic disease. If the anemia is mild, baby is likely to born near his due date, with no need for early inducement [2, 3]. If it is more severe, a blood transfusion can be done in utero (through the umbilical cord) and after birth to replace his blood [2].
