If you just found out you're pregnant, one of the first — and most important — tests you should expect is a blood-type test. This basic test determines your blood type and Rh factor. Your Rh factor may play a role in your baby's health, so it's important to know this information early in your pregnancy.
People with different blood types have proteins specific to that blood type on the surfaces of their red blood cells (RBCs). There are four blood types — A, B, AB, and O.
Each of the four blood types is additionally classified according to the presence of another protein on the surface of RBCs that indicates the Rh factor. If you carry this protein, you are Rh positive. If you don't carry the protein, you are Rh negative.
Most people — about 85% — are Rh positive. But if a woman who is Rh negative and a man who is Rh positive conceive a baby, there is the potential for a baby to have a health problem. The baby growing inside the Rh-negative mother may have Rh-positive blood, inherited from the father. Approximately half of the children born to an Rh-negative mother and Rh-positive father will be Rh positive.
Rh incompatibility usually isn't a problem if it's the mother's first pregnancy because, unless there's some sort of abnormality, the fetus's blood does not normally enter the mother's circulatory system during the course of the pregnancy.
However, during delivery, the mother's and baby's blood can intermingle. If this happens, the mother's body recognizes the Rh protein as a foreign substance and can begin producing antibodies (protein molecules in the immune system that recognize, and later work to destroy, foreign substances) against the Rh proteins introduced into her blood.
Other ways Rh-negative pregnant women can be exposed to the Rh protein that might cause antibody production include blood transfusions with Rh-positive blood, miscarriage, and ectopic pregnancy.
Rh antibodies are harmless until the mother's second or later pregnancies. If she is ever carrying another Rh-positive child, her Rh antibodies will recognize the Rh proteins on the surface of the baby's blood cells as foreign, and pass into the baby's bloodstream and attack those cells. This can lead to swelling and rupture of the baby's RBCs. A baby's blood count can get dangerously low when this condition, known as hemolytic or Rh disease of the newborn, occurs.
In generations past, Rh incompatibility was a very serious problem. Fortunately, significant medical advances have been made to help prevent complications from Rh incompatibility and to treat any newborn affected by Rh disease.
Today, when a woman with the potential to develop Rh incompatibility is pregnant, doctors administer a series of two Rh immune-globulin shots during her first pregnancy. The first shot is given around the 28th week of pregnancy and the second within 72 hours after giving birth. Rh immune-globulin acts like a vaccine, preventing the mother's body from producing any potentially dangerous Rh antibodies that can cause serious complications in the newborn or complicate any future pregnancies.
A dose of Rh immune-globulin may also be given if a woman has a miscarriage, an amniocentesis, or any bleeding during pregnancy.
If a doctor determines that a woman has already developed Rh antibodies, then the pregnancy will be closely monitored to make sure that those levels are not too high. In rare cases, if the incompatibility is severe and the baby is in danger, a series of special blood transfusions (called exchange transfusions) can be performed either while the baby is still in the uterus or after delivery.
Exchange transfusions replace the baby's blood with RBCs that are Rh-negative. This procedure stabilizes the baby's level of red blood cells and minimizes further damage caused by circulating Rh antibodies already present in the baby's bloodstream.
Because of the success rate of the Rh immune-globulin shots, exchange transfusions are needed in fewer than 1% of Rh-incompatible pregnancies in the United States today.
Rh incompatibility rarely causes complications in a first pregnancy and does not affect the health of the mother. But Rh antibodies that develop during subsequent pregnancies can be potentially dangerous to mother and child. Rh disease can result in severe anemia, jaundice, brain damage, and heart failure in a newborn. In extreme cases, it can cause the death of the fetus because too many RBCs have been destroyed.
If you're not sure what your Rh factor is and think you're pregnant, it's important to start regular prenatal care as soon as possible — including blood-type testing. With early detection and treatment of Rh incompatibility, you can focus on more important things — like welcoming a new, healthy baby into your household.
Reviewed by: Steven Dowshen, MD
Date reviewed: November 2011
|American Association of Blood Banks This site of the American Association of Blood Banks describes blood banking and transfusions.|
|American Society of Hematology This group provides information relating to blood, blood-forming tissues, and blood diseases.|
|March of Dimes The March of Dimes seeks to prevent birth defects, infant mortality, low birthweight, and lack of prenatal care.|
|American College of Obstetricians and Gynecologists (ACOG) This site offers information on numerous health issues. The women's health section includes readings on pregnancy, labor, delivery, postpartum care, breast health, menopause, contraception, and more.|
|Medical Care and Your Newborn By the time you hold your new baby for the first time, you've probably chosen your little one's doctor. Learn about your newborn's medical care.|
|Looking at Your Newborn: What's Normal When you first get to see, touch, and inspect your newborn, you may be surprised by what you see. Here's what to expect.|
|Blood Blood is vital to bodily function. Read this article for the basics about blood, blood cells, blood diseases, and more.|
|Jaundice in Healthy Newborns A common condition in newborns, jaundice refers to the yellow color of the skin and whites of the eyes caused by excess bilirubin in the blood.|
|Pregnancy & Newborn Center Advice and information for expectant and new parents.|
|Pregnancy Myths and Tales Even in these times, pregnancy continues to inspire its own set of myths and tales. Which are true and which aren't?|
|10 Things That Might Surprise You About Being Pregnant Despite all the books, websites, and pamphlets devoted to the topic of pregnancy, this 9-month period can take any expectant mom by surprise.|
|FAQs: Prenatal Tests Find out what tests are available to keep you informed of your -- and your baby's -- health throughout pregnancy.|
What to expect when coming to Akron Children's
For healthcare providers and nurses
Residency & Fellowships, Medical Students, Nursing and Allied Health
For prospective employees and career-seekers
Our online community that provides inspirational stories and helpful information.