In what case can a Rh conflict occur during pregnancy?

Rhesus disease occurs during pregnancy when there is an incompatibility between the blood types of the mother and baby.

Everybody has one of 4 blood types (A, B, AB or O). You inherit your blood group from a mix of your parents' genes. These blood types are further identified as being either positive or negative. This shows your 'Rhesus factor' (RhD), which indicates if you have a protein known as 'D antigen' on the surface of your red blood cells.

Around 17 out of 100 people in Australia have a negative blood type. If your blood is RhD negative, it isn’t usually a problem, unless you are pregnant and your baby happens to be RhD positive. This can happen if the baby’s father is RhD positive.

The problem can occur if a small amount of the baby’s blood enters the mother’s bloodstream during pregnancy or birth, the mother can produce antibodies against the rhesus positive cells (known as ‘anti-D antibodies’). This is called a 'sensitising event'.

There are a number of ways that this can occur:

A sensitising event usually doesn’t affect the first pregnancy, but if the woman has another pregnancy with a rhesus positive baby, her immune response will be greater and she may produce a lot more antibodies. These antibodies can cross the placenta and destroy the baby’s blood cells, leading to a condition called 'rhesus disease', or 'haemolytic disease of the newborn'. This can lead to anaemia, jaundice and brain damage in the baby.

Rhesus disease is uncommon these days because it can usually be prevented using injections of a medication called 'anti-D immunoglobulin'. All women are offered blood tests as part of their antenatal screening to determine whether their blood is RhD negative or positive.

The injection is offered at to rhesus negative women who have rhesus positive partners at 28 and 34 weeks of pregnancy. It can also be given at anytime if there is concern a sensitising event has happened. You can also have the injection after the baby has been born and tests confirm your baby is RhD positive. The only way to find out if a baby is RhD positive is after they are born and the umbilical blood can be tested.

The anti-D injection is safe for both the mother and the baby.

If a woman has developed anti-D antibodies in a previous pregnancy (she's already sensitised) then these immunoglobulin injections don't help. The pregnancy will be monitored more closely than usual, as will the baby after birth.

If an unborn baby does develop rhesus disease, treatment depends on how severe it is. A blood transfusion to the unborn baby may be needed in more severe cases. After birth, the child is likely to be admitted to a neonatal intensive care unit (a hospital unit that specialises in caring for newborn babies).

Treatment for rhesus disease after birth can include a light treatment called phototherapy, blood transfusions, and an injection of a solution of antibodies (intravenous immunoglobulin) to prevent red blood cells being destroyed.

If rhesus disease is left untreated, severe cases can lead to stillbirth. In other cases, it could lead to brain damage, learning difficulties, deafness and blindness. However, treatment is usually effective and these problems are uncommon.

During the course of Rh incompatibility, the fetus is primarily affected. The binding of maternal Rh antibodies produced after sensitization with fetal Rh-positive erythrocytes results in fetal autoimmune hemolysis. As a consequence, large amounts of bilirubin are produced from the breakdown of fetal hemoglobin and are transferred via the placenta to the mother where they are subsequently conjugated and excreted by the mother. However, once delivered, low levels of glucuronyl transferase in the infant preclude the conjugation of large amounts of bilirubin and may result in dangerously elevated levels of serum bilirubin and severe jaundice.

Mildly affected infants may have little or no anemia and may exhibit only hyperbilirubinemia secondary to the continuing hemolytic effect of Rh antibodies that have crossed the placenta.

Moderately affected infants may have a combination of anemia and hyperbilirubinemia/jaundice.

In severe cases of fetal hyperbilirubinemia, kernicterus develops. Kernicterus is a neurologic syndrome caused by deposition of bilirubin into central nervous system tissues. Kernicterus usually occurs several days after delivery and is characterized by loss of the Moro (ie, startle) reflex, posturing, poor feeding, inactivity, a bulging fontanelle, a high-pitched shrill cry, and seizures. Infants who survive kernicterus may go on to develop hypotonia, hearing loss, and mental retardation.

A very serious life-threatening condition observed in infants affected by Rh incompatibility is erythroblastosis fetalis, which is characterized by severe hemolytic anemia and jaundice. The most severe form of erythroblastosis fetalis is hydrops fetalis, which is characterized by high output cardiac failure, edema, ascites, pericardial effusion, and extramedullary hematopoiesis. Newborns with hydrops fetalis are extremely pale with hematocrits usually less than 5. Hydrops fetalis often results in death of the infant shortly before or after delivery and requires an emergent exchange transfusion if there is to be any chance of infant survival.

Emergent delivery of an infant with hydrops fetalis should be as nontraumatic as possible. Ideally, a neonatologist who is prepared to perform an exchange transfusion should attend to the infant immediately. [4]

Treatment focuses on preventing the effects of the incompatibility. In mild cases, the baby can be treated after birth with:

Phototherapy involves keeping your baby near fluorescent lights to help reduce the bilirubin in their blood.

These procedures may be repeated until the Rh-negative antibodies and excess bilirubin have been removed from your baby’s blood. Whether it must be repeated depends on the severity of your baby’s condition.

If you’re pregnant and your doctor determines that you’ve already developed antibodies against your baby, your pregnancy will be closely monitored.

You can prevent the effects of Rh incompatibility by getting an injection of Rh immune globulins (RhIg) during your first trimester, during a miscarriage, or while having any bleeding during your pregnancy.

This blood product contains antibodies to the Rh factor. If your baby has Rh-positive blood, you should get a second injection a few days after you give birth.

In very rare and serious cases, a series of special blood transfusions can be performed while your baby is in your uterus or after delivery.

However, the success of RhIg shots has made this treatment only necessary in less than 1 percent of cases of Rh incompatibility in the United States.

The general outlook is good in mild cases of Rh incompatibility.

Rh incompatibility is a mismatched blood type between a pregnant mother and the baby she is carrying. It is rarely serious or life threatening, thanks to early diagnosis and treatment during pregnancy.

Rh factor is a protein located in red blood cells. People who have that protein are Rh-positive. Most people are Rh-positive. People without the protein are Rh-negative. You inherit your blood type from your parents.

If an Rh-positive baby’s blood passes to its Rh-negative mother during pregnancy (or delivery), the mother’s body will attack the baby’s red blood cells. Typically, this is not a concern for a live birth with a first pregnancy. It poses a greater risk in later pregnancies. This is because the mother develops antibodies to attack Rh-positive blood types in future children.

Rh incompatibility isn’t harmful to the pregnant mother. However, it can cause mild to serious medical problems for the baby. Doctors treat the condition by injecting the mother with a Rh incompatibility medicine that protects the baby’s red blood cells.

Path to improved health

In most cases, Rh incompatibility is avoidable with preventive care. Your doctor will check your blood type during your first pregnancy visit. If you have Rh-negative blood, you will be given an injection of Rh immunoglobulin. This happens at around week 28 of your pregnancy. It will be done again within 72 hours of your baby’s birth. It may also be done after a miscarriage, an abortion, or an amniocentesis (a gene screening test done during pregnancy). These are all cases in which the mother and baby’s blood could mix.

According to the American Academy of Family Physicians (AAFP), all pregnant women should have blood typing and Rh testing on their first visit to their doctor for pregnancy care. AAFP recommends retesting between the 24th and 28th weeks of pregnancy.

Rh immunoglobulin will not harm your baby. The injection may cause you to have mild soreness around the injection site. For some pregnant women, common side effects of the medicine include

• Headache
• Mild fever
• Mild pain
• Swelling or redness at the site of the injection

More serious side effects include:

• Severe allergic reaction
• Back pain
• Problems with your urine
• Rapid heartbeat
• Nausea
• Fever
• Trouble breathing
• Unexplained weight gain
• Swelling
• Fatigue
• Yellowing of the eyes or skin

Things to consider

Most Rh-positive babies born from a first-time pregnancy to an Rh-negative mother are not affected by Rh incompatibility. This is because the baby’s blood doesn’t usually pass to the mother’s bloodstream until the time of the birth (vaginal or cesarean section). Exceptions may occur if the mother:

• Had a previous pregnancy that ended in miscarriage or had an abortion.
• Had pregnancy screening tests, such as amniocentesis or chorionic villus sampling (genetic tests that require inserting a needle into the mother’s womb to sample the baby’s cells).
• Had bleeding during her pregnancy.
• Had to have the baby manually rotated from a breech position before her labor started.
• Experienced a blunt trauma injury to her abdomen during her pregnancy.

Once an Rh-positive baby’s blood enters an Rh-negative mother’s bloodstream, a mother’s future Rh-positive babies are at risk for certain medical problems (unless the mother received an Rh immunoglobulin injection). Without that preventive treatment, Rh incompatibility destroys your baby’s red blood cells (hemolytic anemia) during pregnancy. Red blood cells are filled with iron-rich protein (hemoglobin) that supplies oxygen to your baby. Your baby’s red blood cells die faster than his or her body can make new ones.

Without enough red blood cells, your newborn baby won’t get enough oxygen. The baby could suffer from mild conditions, such as anemia (low blood count) and jaundice (yellowing of the eyes and skin). It could also lead to more serious conditions, such as brain damage and heart failure. It’s possible for a baby to die during the pregnancy if too many of their red blood cells have been destroyed.

Questions to ask your doctor

• Does my unborn baby’s blood have to be tested during pregnancy or just mine?
• Does the father’s blood type matter?
• Is blood typing done on pregnant women of all ages?
• What happens if I do not receive the final Rh immunoglobulin injection before my baby is born?

Resources

National Institutes of Health, MedlinePlus: Rh incompatibility

National Institutes of Health, National Heart, Lung, and Blood Institute: Rh Incompatibility

Copyright © American Academy of Family Physicians

This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.