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What Being Rh Negative Means for Your Pregnancy

After finding out I was pregnant with my first child, I excitedly went in for my first prenatal appointment and had the initial blood work done. Much to my surprise, I was told I was "Rh negative." At first, I didn't know what that meant or why it was important—but everything got real when I was told I would have to receive special injections to give the fetus, and any future fetuses, the best chance at survival. Although I was scared at first, my worries were put to rest after I learned more about the condition and its effects on my pregnancy.

The Rh factor, also called the Rhesus factor, is a protein found on the surface of red blood cells. People with Rh-positive blood, about 85 percent of the U.S. population, have this protein; those with Rh-negative blood do not.

If both you and your partner both have Rh-negative blood, there's no need to worry because you'll have an Rh-negative baby. But if you are Rh negative and your partner is Rh positive, your baby could be either positive or negative. A potentially dangerous condition, called Rh Disease, can result when the mother is Rh negative and the baby is Rh positive.

Similar to an autoimmune condition, Rh disease occurs when the Rh-negative mother's body detects Rh factor in the baby's blood and develops antibodies to protect itself. (The body sees the Rh factor as an infection.) The antibodies cross the placenta to fight the Rh-positive cells in the baby's body. As the antibodies destroy the red blood cells, the baby becomes anemic, which can lead to complications like jaundice, heart failure, organ enlargement and possibly death.

The risk of Rh disease during a first pregnancy is low, but it becomes a problem during future pregnancies with other Rh-positive babies. That's because the risk of an attack increases any time your blood mixes with your baby's blood. This can happen during an amniocentesis or a C-section, but also during delivery as the baby exits the body and the placenta is delivered. New research reviewed by Paula Grantham, RN, BSN, and published by the University of Rochester Medical Center suggests that a Rh-negative woman may not always have trouble during her first pregnancy, but she can build a sensitization for subsequent pregnancies. This means that while you may actually carry and deliver a Rhesus-positive baby full term without your body attacking it, your system might become "triggered" so that future pregnancies will likely require treatment in order to prevent your body from attacking the baby.

However, treating a woman with Rh immunoglobulin, or RhoGAM, during her first pregnancy can prevent her body from developing antibodies that could affect her future pregnancies. Because doctors generally don't test the blood type of the baby before birth, Rh-negative moms will require treatment regardless of whether the child is positive or negative. Treatment involves an injection of RhoGAM, which prevents your blood from developing antibodies, around week 27 of your first pregnancy and another injection after the baby is delivered. Some doctors will administer the post-delivery RhoGAM injection only if the baby tests Rh positive, and other doctors give the injection even if the baby tests negative.

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