A negative Rhesus (Rh) test can have some impact on pregnancy due to the risk of blood group incompatibility. However, with appropriate medical care, women and their Rh incompatible fetuses can have healthy pregnancies and deliveries. This is possible if women planning to become pregnant receive good prenatal care, especially screening for the Rh factor.

The Rh blood group system is the second most important blood group after the ABO blood group system in humans. The Rh blood group has very different characteristics from the ABO blood group system, so certain precautions must be taken in blood transfusion as well as in obstetrics, especially when the test result is Rh negative.