Many people have limited understanding of rhesus conflict and its potential consequences. In everyday life, whether you have a positive or negative rhesus factor generally doesn’t affect your health. However, during pregnancy, rhesus conflict can pose serious risks to the fetus and may lead to miscarriage. What is rhesus incompatibility, and what do you need to know about this condition? Read on to find out more.
Rhesus Factor and Rhesus Conflict: Simplified Explanation
The rhesus factor, or rhesus antigen, is a protein located on the surface of red blood cells (erythrocytes). Its presence or absence determines a person’s rhesus blood group. Approximately 85% of people have this protein and are classified as rhesus-positive (Rh+). The remaining 15% lack this protein and are known as rhesus-negative (Rh–). The rhesus factor is inherited and remains unchanged throughout life.
The rhesus factor is a crucial consideration when planning a pregnancy. A child can inherit the rhesus factor from either parent. If the mother is rhesus-positive and the father is rhesus-negative, and the fetus inherits the mother’s blood type, there is no cause for concern. However, if the mother has a negative rhesus factor and the father has a positive one, and the fetus also inherits the positive rhesus factor (Rh+), rhesus conflict may occur.
Rhesus conflict is a condition in which the mother’s body produces antibodies against the fetus’s blood. In other words, the mother’s immune system attacks the fetus’s red blood cells. The likelihood of rhesus conflict during a first pregnancy is low if the mother’s blood is negative and the fetus’s blood is positive. This is because the mother’s immune system has not previously been exposed to Rh+ blood, so antibody production does not occur, and there is no risk of rhesus incompatibility with the fetus.
Risk Factors for Rhesus Conflict During Pregnancy
As mentioned earlier, rhesus conflict can develop if a rhesus-negative woman is carrying a rhesus-positive fetus. When Rh– maternal blood comes into contact with Rh+ fetal blood, the mother’s immune system may not recognize it and produce antibodies. These antibodies are generally too large to cross the placental barrier and harm the baby. Therefore, during the first pregnancy, a full immune response usually does not develop in time.
Rare causes of rhesus conflict that can arise during a first pregnancy include:
- Placental insufficiency: If this condition is present, fetal red blood cells may pass through the placenta and trigger an immune response in the mother.
- Previous erroneous transfusion of Rh-positive blood to a Rh-negative woman.
- Previous miscarriage or ectopic pregnancy.
During the first delivery, the blood of the mother and baby mix, and the mother’s immune system “remembers” the foreign protein. Antibodies begin to form, which can enter the fetal bloodstream. Therefore, if a Rh-negative woman becomes pregnant again with an Rh-positive fetus, the antibodies may attack the red blood cells, leading to increased sensitivity or sensitization.
Other risk factors for developing rhesus conflict during pregnancy include:
- Vaginal bleeding.
- Abdominal trauma.
- Surgical interventions (such as cesarean section) in the medical history or during the current pregnancy.
- Absence of specific immunoprophylaxis following a previous pregnancy with Rh conflict.
- Viral infections (herpetic, cytomegalovirus).
With subsequent pregnancies, the risk of rhesus conflict significantly increases, potentially leading to the development of hemolytic disease of the newborn (HDN), fetal developmental anomalies, and other complications.
Impact of Rhesus Conflict on Pregnancy: Symptoms and Potential Complications
The primary danger of incompatibility between the mother’s and fetus’s blood lies in the development of hemolytic disease of the newborn (HDN)—a condition in which fetal red blood cells are destroyed. The severity of HDN can vary depending on the degree of rhesus conflict.
Possible symptoms and complications of HDN in the baby include:
- Anemia: This occurs due to the destruction of fetal red blood cells. The blood carries insufficient oxygen to the tissues, leading to decreased hemoglobin levels. Oxygen deficiency can adversely affect the development of the fetus’s internal organs and nervous system, causing hypoxia. Severe anemia can be life-threatening for the baby.
- Enlarged Liver and Spleen: This happens when the breakdown of red blood cells leads to an increase in bilirubin, which is toxic in high concentrations.
- Jaundice: This also results from the accumulation of excess bilirubin in the blood.
- Negative Impact on the Heart and Brain: Disruptions in hearing and speech functions may occur due to the intensified breakdown of red blood cells.
- Fetal Hydrops: In rare cases of rhesus conflict, severe generalized edema develops, and fluid accumulates in the body cavities, which can even lead to fetal death.
In terms of the mother’s health, rhesus conflict does not cause direct harm. Apart from concerns for the baby, the expectant mother usually feels normal.
How to Detect Rhesus Conflict Between Mother and Baby
Identifying rhesus conflict based on the mother’s symptoms during pregnancy can be challenging. Symptoms are often absent or similar to those of typical pregnancy-related issues.
The diagnosis of rhesus conflict during pregnancy includes the following steps:
- Determination of Blood Group and Rh Factor: This is the first step in prenatal diagnostics, establishing the mother’s blood group and Rh factor.
- Antibody Testing: Conducted during the initial visit to the doctor and approximately at 28 weeks of pregnancy. A positive result indicates the presence of antibodies and a high risk of rhesus incompatibility, while a negative result suggests their absence and minimal risk.
- Antibody Titer Measurement: Performed when antibodies are detected in the mother’s blood and periodically throughout the pregnancy to monitor their levels. An increase in titer may indicate a higher probability of rhesus conflict.
- Ultrasound Examination: Conducted throughout the pregnancy to monitor the fetus’s condition. The doctor checks the placenta’s thickness, the amount of amniotic fluid, blood flow indicators, and the size of the liver and spleen in the fetus.
In some cases, additional diagnostic tests may be necessary to obtain more detailed information about the fetus’s blood group, the degree of anemia, and potential complications related to rhesus conflict. For instance:
- Amniocentesis: Involves sampling amniotic fluid surrounding the fetus. It helps determine the extent of fetal exposure to the mother’s antibodies.
- Cordocentesis: Performed to obtain a blood sample from the umbilical cord to assess the degree of damage to fetal blood cells. This helps determine whether an urgent blood transfusion is needed.
If rhesus conflict is confirmed, the mother may require monitoring at a specialized perinatal center to ensure regular care for both her health and the fetus’s condition.
Prevention of Rhesus Conflict
A key recommendation for Rh-negative patients during pregnancy to prevent sensitization and complications associated with hemolytic disease of the newborn (HDN) is the administration of anti-D immunoglobulin (Rho(D) immunoglobulin). This medication suppresses the immune response, prevents the production of Rh antibodies, and significantly reduces the risk of fetal red blood cell destruction in subsequent pregnancies.
A prerequisite for administering anti-D immunoglobulin is the absence of anti-Rh antibodies in the mother’s blood. If these antibodies are already present, prophylaxis will be ineffective.
Conditions for Administering Anti-D Immunoglobulin During Prenatal Prophylaxis:
- At 28 weeks of pregnancy.
- At the first signs of a threat to pregnancy before 28 weeks (e.g., bleeding).
- After events that may lead to the mixing of fetal and maternal blood (e.g., miscarriage, ectopic pregnancy, amniocentesis, abdominal trauma, or vaginal bleeding during pregnancy).
Postnatal Prophylaxis involves administering anti-D immunoglobulin within 72 hours after the birth of an Rh-positive baby. As the effect of the medication gradually diminishes, it needs to be administered with each new pregnancy.
It is worth noting that modern methods allow for the determination of the fetal Rh factor through maternal blood as early as the first trimester of pregnancy (starting from the 10th week). Therefore, Rh incompatibility prophylaxis with anti-D immunoglobulin can be administered timely and only when necessary.
General Advice for Pregnant Women (especially those confirmed to be Rh-negative):
- Register for prenatal care in a timely manner (around 11-13 weeks of pregnancy).
- Determine the blood group and Rh status of both the mother and the father of the unborn child.
- If the mother is Rh-negative, follow the doctor’s recommendations.
- At 28 weeks of pregnancy, consult with a specialist about the need for Rh incompatibility prophylaxis with anti-D immunoglobulin.
- Administer prophylaxis with anti-D immunoglobulin immediately after the birth of an Rh-positive baby.
According to Dr. Robyn Horsager-Boehrer, MD, Head of the Department of Obstetrics and Gynecology at the William P. Clements Jr. University Hospital, Southwestern Medical Center (Texas, USA), timely prophylaxis with anti-D immunoglobulin is highly effective in preventing the negative consequences of immune incompatibility, particularly those associated with HDN complications.
Is Treatment for Rhesus Conflict Possible During Pregnancy
There is no specific treatment for rhesus conflict during pregnancy. Therapeutic measures depend on the severity of hemolytic disease of the newborn (HDN). Without treatment, approximately 50% of cases may result in brain damage or fetal death.
If HDN leads to life-threatening anemia or edema in the fetus, an intrauterine transfusion may be performed. This involves transfusing compatible blood into the fetal umbilical vessels to replenish red blood cells and improve the fetal condition. This procedure can extend the pregnancy by about four weeks.
After an intrauterine blood transfusion, specialists may decide to proceed with an early cesarean section. This is done to prevent the fetus from receiving additional harmful maternal antibodies, thereby reducing the likelihood of further injury and hypoxia. If no life-threatening conditions are confirmed, the pregnancy may continue to full term without premature delivery.
After birth, infants with rhesus conflict and HDN may require specialized treatment, such as phototherapy for jaundice or blood transfusions for severe anemia.
Conclusion
The presence of rhesus conflict during pregnancy can have serious consequences for the infant. However, timely measures to prevent an immune response from the mother’s body can help avoid the development of rhesus conflict, hemolytic disease of the newborn (HDN), preterm labor, or even fetal loss. Timely prevention through the administration of anti-rhesus Rho (D) immunoglobulin can prevent sensitization and complications related to rhesus incompatibility and HDN during pregnancy.