Q. My husband and I have different blood types. I'm AB negative and he’s O positive. Is this something we need to be worried about before I get pregnant?
A. No. There are four basic blood types: A, B, AB, and O; these types have nothing to do with general health, and having a different type than your partner has no bearing on fertility or pregnancy. But the Rh factor—the “positive” or “negative” after the letter—is another story. The Rh factor is a type of protein on the surface of red blood cells. If you don’t have this factor (i.e., blood type is “negative”), but your husband does, there’s a chance that the baby will have positive Rh blood, too. Then if your blood and the baby’s mingle (which usually happens at delivery, but can happen before), you can produce antibodies against that factor, which can be a risk in subsequent pregnancies. This is true even if your first pregnancy ends in a miscarriage or termination. To prevent such sensitization, injections of Rh immune globulin (RHIg, trade name RhoGAM) may be given at 28 weeks and/or after delivery.