Pregnancy and Alloimmunisation

Rh+ve or Rh-ve???

Something which is not meaningful and important to you in your everyday life, but it does become important when you’re trying to get pregnant.

What is Rh Sensitisation? Mother and child’s relationship is unique, its full of love and care but the mother also passes Rh factor to the baby. If the women are Rh-ve there is no Rh factor on them whereas Rh +ve will definitely have this marker. So if Rh-ve women blood mixes with Rh+ve, the immune system becomes active and destroys Rh factor by making antibodies to it. This mechanism is called Rh sensitization.

Causes leading to Rh Sensitisation during Pregnancy?

Rhesus sensitization was discovered way back in 1939. 

It can occur in 3 conditions:

1. The fetus is Rh+ve and mother is Rh-ve

2.Mothers immune system produces an antibody against D antigen

3. Fetal erythrocytes sufficient in number gain access to maternal circulation in most cases, the baby’s blood will not mix up with your blood until delivery. 

Your first pregnancy would probably not be affected but your subsequent pregnancy with Rh+ve baby does get affected as IgG antibodies are found and they cross the placenta.

Risk factors affecting Rh sensitization:

Factors that increase Fetomaternal hemorrhage in the antepartum period:

Miscarriages

Ectopic pregnancy 

chronic villus sampling & Amniocentesis

Abdominal Trauma and Abruptions

External Cephalic Version

During Delivery:

Caesarean’s

Multiple pregnancies

Placenta Previa

Manual removal of placenta or any intrauterine manipulations

Who are at risk of getting sensitized to Rh disease during pregnancy? Rh-ve is at risk and the Risk is greater if you have been pregnant before. There are no signs and symptoms and blood tests are the only way to know if your sensitized or not. If sensitization has already taken place, your baby can be protected and in cases where both parents are having a negative blood group then the baby will Also have a negative blood group, and sensitization will not occur.

How can Rh sensitization be prevented? It can be prevented by giving Rh anti D immunoglobulin. It can be given at 28 weeks of pregnancy and next can be repeated after delivery if the baby is Rh+ve It will not work in women who are already Rh sensitized. Complications of Rh disease? 

The complication in utero may include:

Anemia in baby leading to liver and spleen enlargement

Jaundice

Hydrops Fetalis-Large amount of fluids get deposited in your baby’s tissue and organs due to severe anemia.

After the baby’s birth, there can be 

Severe Jaundice or Kernicterus.

How can Rh sensitization be diagnosed and its treatment?ABO and Rh Blood group of all patients should be done at the first visit. If a woman is Rh-negative it is important to know the Rh status of the partner. If a partner is Rh-ve no further investigation is required.If the partner is Rh+ve an Indirect Coombs test is advised to detect the presence of anti D antibodies in Rh-ve women irrespective of her parity. If antibody not detected in the first test, the second test should be repeated at 28-32 weeks, and if ICT is negative at 28 weeks no further tests required, and ani D immunoglobulin is to be given. 

With the first pregnancy risk of fatal disease is low but subsequent pregnancy severity increases. If Rh Alloimmunization occurs than pregnancy will be carefully monitored with: 

Blood tests to check for antibodies

Doppler USG every 1-3 weeks to check for fetal hydrops

Amniocentesis is to be done after 18 weeks of treatment of baby will depend upon fetal anemia and hydrops status: If anemia is mild more testing is required for pregnant women and no further treatment is required for the baby. If anemia is getting worst than blood transfusion or treatment of jaundice is required after delivery.For severe anemia, blood transfusion is required in utero and keeps the baby healthy till it’s mature enough to be delivered and might need a blood transfusion after delivery too.

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