New Test Targets Pregnancy Disorder

A new test can identify whether a mother and her baby have different blood types. The test is accurate, feasible, and it could significantly reduce unnecessary treatment.

If a mother's blood type is Rhesus- (Rh)-negative and she is carrying a baby whose blood is Rh-positive, complications can occur. Blood that is Rh-positive contains an RhD antigen that passes into the mother's blood during birth. This substance causes the mother to make antibodies against the RhD-positive blood. Problems do not occur during a woman's first pregnancy but, if the woman has another RhD-positive baby, the antibodies can cross the placenta and invade the baby's red blood cells. This results in hemolytic disease--a blood disorder that is serious and can cause death.

Generally, the blood type of pregnant women is determined at their first antenatal visit. If the woman is RhD-negative, she is given one or two antiserum injections of anti-RhD immunoglobulin during the pregnancy. However, because about 38% of RhD-negative women are carrying a baby who is also RhD-negative these women receive unnecessary treatment of antiserum injections.

To avoid unnecessary treatments scientists at the [UK] National Health System (NHS) Blood and Transplant Center in Bristol (UK; www.uktransplant.org.uk) studied a new way to predict a baby's blood group by typing its DNA in the plasma of RhD-negative pregnant women. "Our results show that fetuses of RhD-negative women could be RhD genotyped with an acceptable level of accuracy,” wrote the authors of an article describing the study, which appeared online in the British Medical Journal (BMJ) in April 2008. They also pointed out the low rate of false-positive results. "The introduction of fetal genotyping followed by the withholding of antenatal anti-RhD prophylaxis from mothers with an RhD-negative fetus would result in about 36% of women being saved from unnecessary exposure to human blood products, inconvenience, and discomfort.”


Related Links:
[UK] National Health System Blood and Transplant Centre