Rh alloimmunization is a condition that may occur during pregnancy if a woman has Rh-negative blood and the fetus has Rh-positive blood. In this case, the mother’s immune system may begin to produce antibodies against the baby’s red blood cells, recognizing them as foreign. Without timely prevention, this can lead to serious complications, including fetal anemia. That is why knowing your blood type and Rh factor plays a key role in safe pregnancy management.
How to find out your blood type:
• take a blood test in a laboratory
• check your medical records or hospital discharge summary
• undergo testing when preparing for pregnancy
During pregnancy, blood type testing is обязательно performed at the first medical visit.
What does Rh-negative blood mean?
The Rh factor is a protein on the surface of red blood cells:
• If the protein is present → Rh-positive blood
• If the protein is absent → Rh-negative blood
By itself, the Rh factor does not affect a woman’s health. However, it becomes important during pregnancy.
Rh incompatibility during pregnancy
If a woman is Rh-negative and the baby is Rh-positive, Rh incompatibility may occur.
How it happens:
• Normally, maternal and fetal blood do not mix
• Sometimes (most often during delivery), a small amount of fetal blood enters the maternal bloodstream
• The mother’s immune system recognizes it as “foreign” and produces antibodies
In a subsequent pregnancy, these antibodies may:
• cross the placenta
• destroy the baby’s red blood cells
• cause fetal anemia
How to determine the baby’s blood type?
Before birth, this is difficult, but there are some indications:
• If both parents are Rh-negative → the baby will also be Rh-negative
• If the father is Rh-positive → the baby may be either Rh+ or Rh−
In some cases, the fetal Rh factor can be determined through a maternal blood test, but this test is not available everywhere.
What to do if you are Rh-negative?
During pregnancy, your doctor will:
• regularly check your blood for antibodies
• prescribe preventive treatment if antibodies are absent
Prevention of Rh incompatibility is carried out using anti-D immunoglobulin (RhoGAM). It helps prevent the formation of antibodies.
When the medication is given:
• in the third trimester of pregnancy
• after delivery (if the baby is Rh-positive)
• in case of bleeding during pregnancy
• after amniocentesis or other procedures
• after miscarriage or ectopic pregnancy
If antibodies are already present, prevention is no longer effective. In such cases, the doctor provides closer monitoring, assesses the condition of the fetus, and prescribes treatment if necessary.
Planning future pregnancies
If you are Rh-negative, prophylaxis is carried out during each pregnancy. Regular medical follow-up is important, as timely management helps prevent complications in the vast majority of cases.