Pregnancy in Rh-Negative Woman (Rh Incompatibility)

What is Rh Factor?

Rh factor is a type of antigen (protein) usually found on the human red blood cells discovered by Landsteiner and Weiner in 1940. The individual having the antigen is called Rh-positive and in whom it is not present, is called Rh-negative.

About 85% are Rh-positive and a small percentage of people are Rh-negative. This antigen is inherited from parents at birth.

Rh incompatibility occurs when an Rh-negative woman is pregnant with an Rh-positive fetus where Rh factor is a type of protein found on the red blood cells.

What is Rh incompatibility?

Rh incompatibility can occur when a woman with an Rh-negative blood type is pregnant with a foetus with an Rh-positive blood type.

The Placenta usually acts as a barrier between the mother and the foetus. When an Rh-negative mother bears an Rh-positive foetus; during labour and delivery or procedures such as abortion, amniocentesis and antepartum haemorrhage; the fetal blood cells cross the placenta and enter the circulation of the mother.

The Mother’s immune system starts to react by producing anti-D antibodies against the baby’s red blood cells that cause sensitization. Antibodies are a part of the body’s immune system and destroy foreign substances. Once a woman is sensitized, Rh antibodies remain in the system.

Rh sensitization does not harm the baby during the first pregnancy. If the mother is Rh-negative and the baby is Rh-positive, it means that the baby has inherited the genes from his/her father.

Rh incompatibility
Rh incompatibility

How is fetus affected by the Rh antibody?

In subsequent pregnancies, the antibody formed in the mother’s system (IgG) crosses the placental barrier and enters into the fetal circulation.

These antibodies will not affect the baby with Rh-negative blood type but if the foetus is Rh-positive, the antibody gets attached to the surface of the fetal red blood cells and starts to destroy them. This causes hemolytic diseases in the baby.

What are the symptoms of Rh incompatibility?

Rh incompatibility can cause mild to life-threatening symptoms.

When the mother’s antibody attacks the fetal blood cells, excessive destruction of the foetal red blood cells leads to severe anaemia and rise of bilirubin (chemical that is formed from the breakdown of red blood cells) level in the baby.

When the fetus is in-utero, the liberated bilirubin is mostly excreted through the placenta into the mother’s system and the baby is not born with jaundice. But as soon as the umbilical cord is clamped, the continuing destruction increases the bilirubin concentration and the baby becomes jaundiced within 24 hours.

The baby may have the following symptoms due to a rise in bilirubin level after birth are-

  • Yellowish discoloration of the skin and sclera of the eyes.
  • Low muscle tone
  • Fever
  • Poor feeding
  • Lethargy

Symptoms usually subside after treatment.

How is Rh incompatibility is diagnosed?

It is diagnosed for the first time during a prenatal visit. A blood test is carried out to determine the Rh factor. If found Rh-negative, the partner may also be tested. If the partner is found Rh-negative, nothing is there to worry about. If the partner is found Rh-positive then the doctor will suggest further interventions.

The doctor can also test the baby’s blood to check the maternal antibodies that are destroying the baby’s red blood cells.

How to prevent Rh incompatibility?

An Rh-negative mother with an Rh-positive baby can be immunized with Rh anti-D immunoglobulins(IgG). It should be administered intramuscularly to the unimmunized mother within 72 hours following delivery or abortion.

If a blood test indicates that a mother is Rh-negative and the baby is Rh-positive then the doctor may administer anti-D IgG, during the first trimester of pregnancy and a second dose after birth. This drug stops the immune system from making antibodies against the fetal cells. If the mother’s blood already has antibodies then the drug won’t work and the doctor has to keep a close watch on the baby’s health during pregnancy and take appropriate interventions following birth.

Prevention of feto-maternal bleed during procedures such as Caesarean section, amniocentesis, manual removal of the placenta and abortions.

To avoid giving Rh-positive blood to one Rh-negative female from her birth to menopause.

How is Rh incompatibility treated?

In mild cases, the baby can be treated after birth with the following interventions

  • Phototherapy – Involves keeping the baby under fluorescent light to reduce the bilirubin level in the blood.
  • Intravenous infusions includes fluids and electrolytes to regulate the metabolism.
  • Blood transfusions.

In severe cases, a series of blood transfusions are required during pregnancy (fetus in-utero) and after delivery.


In the above post, we discussed the Rh factor, Rh incompatibility, fetus affection by the Rh antibody, symptoms, diagnosis, prevention and treatment.

Thank you!!! Hope you find this useful.

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