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He's Positive, She's Negative: What's That Do to Baby?

He's Positive, She's negative; What's That Do To Baby?

By Carolyn Strange
WebMD Feature

A: It's always a good idea for any couple to think ahead and prepare for pregnancy, so Mom and baby can be as healthy as possible. When facing the potential for Rh disease, as you two are, it's even more important. You'll probably want to educate yourselves about Rh incompatibility. And in any case, make sure you find a health-care provider who understands Rh disease, and with whom it's easy to communicate.

One thing is clear -- your baby will have type O blood. What's not clear is whether your baby's blood will be Rh-positive or Rh-negative, and that's what makes all the difference.

Rh disease of the newborn arises from incompatibility of the Rh factor between the mother and baby. It's a bit simplistic, but you can think of the Rh factor as a protein that is either present (positive) or absent (negative) on red blood cells. Exact percentages vary with race, but most people are Rh-positive.

A woman with Rh-negative blood has nothing to worry about if her baby is also Rh-negative, and a woman with Rh-positive blood need not worry at all. Problems arise only with Rh-negative mothers and Rh-positive babies. Usually the first pregnancy goes fine. It's a subsequent Rh-positive baby who may be at risk. The mother herself is in no danger.