What should a Rh negative woman know?

It happens that, during a consultation, patients who are considering pregnancy draw the doctor's attention to the fact that they have Rh-negative blood and wonder if this could lead to complications during pregnancy. In this article, we will look at what blood type and Rh factor are, and whether Rh-negative blood is actually associated with risks for the health of the future mother or the baby.

On the surface of red blood cells (erythrocytes) are specific proteins (antigens), based on the presence or absence of which blood types are classified. The most important classifications are the ABO system (known as blood type) and the Rh factor (Rh).

The main blood types according to the ABO system are as follows:

• Blood type O (I): no antigens (universal donor of red blood cells).
• Blood type A (II): presence of A antigens.
• Blood type B (III): presence of B antigens.
• Blood type AB (IV): presence of both A and B antigens.

The Rh factor (Rh) is the second clinically relevant blood classification after the ABO system. It was named after the Rhesus monkey in which the factor was first discovered. The key antigen is the D antigen. If it is present on the surface of red blood cells, the blood is considered Rh positive (Rh+); otherwise, it is Rh negative (Rh-).

Most of the planet's inhabitants, about 85%, are Rh(+) positive; the others are Rh(-) negative.

Determining blood type and Rh factor is particularly important in the case of blood transfusions and during pregnancy. In the case of a blood transfusion, incompatibility with these two systems can pose a serious threat to the patient's health and life. ABO group antigens are detected in the embryo's erythrocytes starting from 5-6 weeks of gestation, and the Rh factor (Rh) from the 8th week.

Blood group or Rh incompatibility between the mother and the embryo can lead to the production of specific antibodies and immune reactions (sensitization), which most often manifest as hemolytic disease of the fetus and newborn (neonatal jaundice).

ABO Incompatibility

ABO incompatibility is more common with blood type O (I) in the mother and A (II) in the father (and the fetus) because the A antigen has the strongest antigenic properties. Hemolytic disease in the case of ABO incompatibility is very rarely severe, and if it occurs, it manifests as mild anemia or jaundice in the baby.

A negative blood type during pregnancy does not always pose a threat to the baby. For example, there can be different combinations:

• Rh(-) parents will have an Rh(-) child: the blood of the fetus and the mother are similar, there will be no conflict.
• If the mother is Rh(-) and the father is Rh(+) and they have an Rh(-) child, the pregnancy proceeds without issues.
• If the mother is Rh(+) and the baby is Rh(-), there is no protein incompatibility.

Problems arise when an Rh(-) mother has an Rh(+) child. The woman's blood may start producing antibodies to destroy the foreign proteins of the baby. However, if the Rh(-) woman is pregnant for the first time and there has been no previous transfusion of incompatible blood or abortion beyond 8 weeks, there is no cause for concern. The mother's blood has not yet come into contact with foreign red blood cells and has not learned to "fight" against them.

What to know about Rh(-) women during pregnancy:

1. It is advisable to determine the blood type and Rh factor of your own blood and that of the man as soon as pregnancy planning begins (sometimes, the father's blood test can also rule out the presence of Rh-positive blood in the child).
2. Around the 12th week of pregnancy, the blood type and Rh factor of your baby can be determined through a blood test, the non-invasive prenatal RhD NIPT test, performed on you (if your baby is Rh(-), he is not at risk of Rh disease and will not require additional monitoring or treatment).
3. If an Rh(-) woman is at risk of Rh conflict during pregnancy, a blood test for antibody screening should be performed every month until the 28th-32nd week of pregnancy.
4. If the antibody screening is negative, your obstetrician/gynecologist will prescribe anti-Rh immunoglobulins around the 28th week of pregnancy, and then within 72 hours after delivery (if the fetus is Rh positive), to prevent the formation of antibodies in subsequent pregnancies.
5. If the antibody screening is positive, special attention is given to ultrasound examination of the fetus and monitoring of the antibody titer in the mother's blood (after the 32nd week of pregnancy, twice a month, and from the 35th week, once a week).

Artificial Insemination and Rh Incompatibility

Particular attention should be paid to Rh incompatibility when planning a pregnancy through artificial insemination (IVF) or intrauterine insemination (IUI). In the case of in vitro fertilization, there may be a risk of conflict due to the specifics of ovulation stimulation and hormone therapy, which increase the woman's immune response to foreign antigens.

Rh(-) women should discuss in advance with their doctor the risks of Rh conflict, as well as the possibility of prophylactic therapy with Rh immunoglobulins in the early stages of pregnancy preparation. For future mothers undergoing IVF, it is important to control the Rh factor of the intended donor (if donor eggs or sperm are used) to minimize the likelihood of conflict and ensure healthy fetal development.

Thus, Rh-negative blood does not threaten the health of the future mother and does not pose a risk for the first pregnancy of an Rh baby. However, the pregnancy of an Rh(+) baby requires close monitoring in Rh(-) women with complicated obstetric histories or histories of blood transfusion.