Determining and Managing Rh Incompatibility

by Alan Greene, MD, FAAP

Every snowflake is different and each person is even more so! Each cell in our bloodstream carries our own genetic signature. A constellation of proteins on the surfaces of the cells allows our bodies to distinguish between our own blood and someone else's. These protein patterns are roughly divided into groups that we call blood types.

Not only are blood types different but some types of blood are incompatible with some others. The white blood cells in some types will perceive other types as enemies, attacking and destroying the other blood. This problem is most significant in people with Rh incompatibility.

People are called Rh-negative if they do not have the rhesus (Rh) protein on the surfaces of their blood cells. If Rh-positive blood cells get into the bloodstream of someone who is Rh-negative, the body of that Rh-negative person will see this as an enemy invasion.

Unprepared, the Rh-negative person will begin to make antibodies (what you call anticorps) against the foreign Rh protein. This first exposure is often not even noticed. The next time an exposure occurs, though, the body is primed to seek and destroy all Rh-positive blood cells. All-out war can occur inside an Rh-negative person's body.

A terrible condition called hydrops fetalis can be the result of that war. Rh incompatibility produces a wide variety of outcomes. Sometimes only mild anemia and perhaps a little jaundice are the only signs there has been a conflict.

But sometimes the results are catastrophic. The first pregnancy is rarely a problem because blood is often not exchanged until the time of birth. But with each subsequent pregnancy, the risk for hydrops increases.

Hydropic babies are bloated, swollen, and pale. Enlarged hearts, livers and spleens are unable to perform their vital duties. The swollen lungs can make breathing impossible. Many die shortly after birth. Many hydropic babies are stillborn.

In 1963 an event occurred that began to change the story. Jorg Schneider, who was at the Freiburg University Hospital in Germany at the time, became the very first investigator to give pregnant, Rh-negative women a shot of Rh antibodies to prevent their immune systems from mounting their own response to Rh-positive cells.

The exact date of this achievement was August 9, 1963. One year later, Schneider reported that nine women, following delivery of Rh-positive children, did not develop Rh antibodies during subsequent pregnancies with Rh-positive fetuses.

Since then, prevention programs have been implemented in many countries around the world. In Great Britain, the number of deaths from hydrops has dropped 96% in the years since the prevention program began in 1970.1 This experience is typical.

By giving anti-D globulin (RhoGAM) to Rh-negative moms during and shortly after each pregnancy (including after miscarriages and abortions), 99% of mothers will not develop anti-Rh antibodies.2Unfortunately, about 1% still do.

Being Rh-negative is a recessive trait. This means that a person needs to have two negative genes to be Rh-negative and will always give one negative gene to any offspring. Being Rh-positive is a dominant trait. This means that an Rh-positive person can have two positive genes or one positive and one negative gene. If your husband has a positive and a negative gene, then about half of your offspring will be Rh-negative (and there should be no trouble carrying an Rh-negative child). But about half of your offspring will be Rh-positive (and if your mate has two positive genes, all of your offspring will be Rh-positive). This is a very risky proposition.

Healthy, Rh-positive children have been born to women with high titers, especially if they have had the RhoGAM and the titers are still high. Having a blood type B mom and a blood type A baby is also somewhat protective. But the pregnancy should be monitored closely and carefully managed by an expert in this area, even before conception. For a successful outcome, the baby may need blood transfusions every 3 to 5 weeks even before being born. Delivery is induced as early as is safe.

Even if birth is successful, the infant should be cared for at a well-prepared medical center. The baby may need aggressive treatment for anemia, immunodeficiency, and jaundice shortly after birth.3

When I was born, hydrops fetalis was an almost hopeless situation. Today, preventing Rh-negative moms from being sensitized is extremely (but not completely) successful at preventing hydrops wherever the guidelines are followed. All of this with a couple of simple, but ingenious shots! Once a mom has become sensitized things are not so simple. Future pregnancies may turn out fine, but sometimes massive, complex, medical interventions are necessary -- and even with these, a good outcome may not be possible.

Dr. Alan GreeneDr. Alan Greene, author of Raising Baby Green and Feeding Baby Greene, is the founder of Dr.Greene.com and the WhiteOut Movement. He is a frequent guest on such shows as Good Morning America, The Today Show, and the Dr. Oz Show. He is on the Board of Directors of Healthy Child Healthy World and The Lunchbox Project. Dr. Greene is a practicing pediatrician at Stanford University's Packard Children's Hospital.

Copyright © Greene Ink, Inc., all rights reserved. Permission to republish granted to Pregnancy.org. Reviewed by Khanh-Van Le-Bucklin M.D. & Liat Simkhay Snyder M.D. November 8, 2008.