When a woman finds out that she is pregnant and she starts her prenatal visits, doctors usually draw some blood. This blood is tested to find out the woman’s blood type. The results will form the basis for her medical schedule throughout her pregnancy.
There are four blood types that exist: A, B, AB and O. Women can also have a situation where proteins appear on the surface of their blood. This is known as Rh factor. Where this is the case, it is classified as Rh positive (that is A+, B+, AB+ and O+) and those without are Rh negative (meaning A-, B-, AB-and O-).
Your blood type plus Rh factor and your partner’s will have an effect on your baby’s blood type. It will however also influence the type of antibodies that your body creates in an attempt to protect itself from foreign items like sperm, bacteria or an embryo. In the event that you are Rh negative and your baby is Rh positive, it is known as Rh incompatibility. Your body will act like your baby’s blood is foreign and will create antibodies against them and if the two blood types mix, the baby’s blood will be attacked by yours. This is known as Rhesus disease.
Another type of blood-related problem is ABO incompatibility. This is where a mother’s blood type is O while the baby’s is A or B. The mother produces antibodies that attack the red blood cells in the baby’s blood when the twoblood types mix.
During your first pregnancy, your baby is protected throughout until birth since your blood can’t cross through the placenta although small amounts from the baby can cross over to the mother. There are some instances where the mixing of blood between the two is inevitable and sooner than expected. These include:
- An injury that causes bleeding such as in a car accident
- An ectopic pregnancy
- If a placenta sample is taken for testing (CVS)
- After taking some blood from the umbilical cord for testing (amniocentesis)
The antibodies that develop in such scenarios can cause severe anemia and jaundice in the baby. If there is Rh incompatibility, whenever you are pregnant with an Rh positive baby your body will produce antibodies in higher amounts. ABO incompatibility is different in that it doesn’t worsen with subsequent pregnancies. It will however continue to affect the baby until all the antibodies have been passed out of its system after birth.
How is it dealt with?
A baby’s blood group remains unknown throughout pregnancy therefore precautionary measures are taken on the mother. Every Rh negative woman is given anti-D injections during pregnancy to prevent Rhesus disease. This is done at 28 and 34 weeks. Blood from the umbilical cord is collected to find out the baby’s blood group. If positive, another injection is given and if negative the injections aren’t needed.
The injections given are effective in stopping the development of Rh antibodies. This allows an Rh negative woman to carry other pregnancies without incompatibility complications. In the event that Rh disease has already been diagnosed during pregnancy, the woman will require close monitoring. This will ensure that the baby remains healthy and unharmed throughout using ultrasound.
If the baby’s blood count gets very low at any point, special blood exchange transfusions can be made using the umbilical cord so as to stop the reduction of red blood cells. Sometimes the baby may have to be delivered earlier. Such measures are rarely required though because the anti-D injections are very effective.
There is no way of preventing ABO incompatibility but if the baby develops anemia or jaundice, they will be taken through phototherapy to break down the chemicals causing jaundice and a blood transfusion to deal with the anemia.