What is the benefit of determining the Rh factor before birth?
A new blood test can be used to determine the rhesus (Rh) factor of an unborn baby during pregnancy. That can help to decide whether it makes sense to give Rh-negative women an anti-D injection. This prenatal test is not expected to have any drawbacks.
The rhesus factor is an important characteristic of blood cells. It indicates whether the blood of two different people is compatible when mixed – such as the blood of a mother and her baby at birth. If they have different blood group characteristics, it may cause problems.
The rhesus factor D (RhD), a protein found on the surface of the red blood cells, determines whether the mother’s blood and the baby’s blood will be compatible. It is also referred to as the RhD antigen. Most people have it, and are then said to be “Rh positive” (rhesus positive). Someone who lacks it is “Rh negative” (rhesus negative). In Europe, this is roughly 15% of the population.
If a pregnant woman is Rh positive, that won't cause any health problems – regardless of whether the baby is Rh negative or Rh positive.