Final answer:
Pregnant women are generally tested for their blood type (A, B, AB, or O) and their Rhesus (Rh) factor. This is important to know because Rh- mothers with an Rh+ fetus can develop antibodies that may lead to hemolytic disease of the newborn in later pregnancies. Ultrasounds are the safest imaging study during pregnancy, and a type AB/Rh- person would only have Rh antibodies in their blood.
Step-by-step explanation:
The type of testing ordered on all pregnant women generally includes blood type, which can be A, B, AB, or O, and the Rh factor, indicating the presence or absence of the Rh antigen on the surface of red blood cells.
A type AB mother carrying a type O fetus or a type O mother carrying a type AB fetus would be noteworthy situations because an Rh- mother carrying an Rh+ fetus could lead to hemolytic disease of the newborn if preventive measures are not taken. The risk is especially notable during a second pregnancy with an Rh+ fetus if the mother has become sensitized during the first pregnancy and was not treated with RhoGAM.
The use of ultrasound is considered safe during pregnancy according to the options given, being preferred over CT scans, PET scans, and X-rays due to its non-ionizing nature. This fact is supported by the information that a pregnant person receives an ultrasound as part of their prenatal care. Those with Rh- blood and who have Rh+ offspring are at risk of producing anti-Rh antibodies, which could lead to hemolytic disease of the newborn in subsequent Rh+ pregnancies if untreated.
If a person has blood type AB/Rh-, they will not have any A or B antibodies in their blood, but they can have Rh antibodies if they have been sensitized to Rh+ blood through prior pregnancies or transfusions.