Rh+, Rh-, and Rhogam
Once the pregnancy test comes back positive, most expectant mothers are anxious
to go in for their first prenatal appointment. This doctor appointment will be considerable in length. You will receive a thorough medical exam. Your doctor or midwife will order various tests such as urine analysis, a PAP smear and blood work. The blood test will determine your blood type (A, B, AB, or O) and your Rh status. The blood will also be screened for Rh antibodies.
Rh status describes whether or not you have the Rh factor, a protein on the surface of red blood cells. If you don't have the Rh factor, you are considered Rh-negative; if you have it, you are Rh-positive. Most people (about 85 percent) are Rh-positive.
This number is higher for certain ethnic populations; 90-95 percent of African Americans are Rh-positive, and for Asians, the figure is 98 to 99 percent. Rh status matters only when you're pregnant and only if you are Rh-negative and the baby's father is Rh-positive. If this is the case there is a chance the baby will have the Rh factor (be Rh-positive). It isn't usually dangerous during a first pregnancy because the immune response isn't as strong.
The response will get stronger however, with each future pregnancy. In subsequent pregnancies, if your baby is Rh-positive, your antibodies can cross the placenta and begin to attack your baby's red blood cells. This is known as Rh disease. At one time Rh disease caused problems ranging from severe jaundice and the need for blood transfusions at birth to miscarriages and stillbirths.
With the treatments available today, complications from being Rh-negative and carrying an Rh-positive baby pose very little threat. If you are Rh-negative, you will be given an injection of Rh-immune globulin (RhoGAM) between weeks 28 and 29 of your pregnancy. After delivery, if your baby is Rh-positive, you'll be given another shot within 72 hours. These shots almost always prevent the mother from producing antibodies against Rh-positive cells, protecting you for future pregnancies.