TME 69: The Indirect Antiglobulin Test (IAT/ICT) in Pregnancy: Why ALL Expectant Mothers Need It

Pregnancy brings joy but also requires important medical tests to protect both mother and baby. The Indirect Antiglobulin Test (IAT), also called the Coombs test, is one such crucial screening that every pregnant woman should have, regardless of blood type.

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What Is the Indirect Antiglobulin Test (IAT)?

The IAT is a blood test that detects harmful antibodies in the mother's blood that could attack the baby's red blood cells. While commonly associated with Rh (D) incompatibility, it also screens for other dangerous antibodies that many women don't know they carry.

What Does the IAT Detect?

✅ Anti-Rh(D) antibodies (the most well-known risk for Rh-negative mothers)

✅ Other clinically significant antibodies (Kell, Duffy, Kidd, MNS, and more)

✅ Irregular antibodies that could cause hemolytic disease of the fetus and newborn (HDFN)

If these antibodies cross the placenta, they can destroy the baby's red blood cells, leading to severe complications.

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Who Should Be Tested? (Spoiler: EVERY Pregnant Woman!)

Myth: "Only Rh-negative women need the IAT."Fact: All pregnant women should be screened, regardless of blood type.

Why?

1. Minor Blood Groups Matter

   • We routinely test for ABO and Rh (D), but there are hundreds of other blood group systems (Kell, Duffy, Kidd, MNS, etc.).

   • Even Rh-positive mothers can have antibodies against these minor groups.

2. Prior Pregnancies or Transfusions Increase Risk

   • Women who have had:

     • Previous pregnancies (including miscarriages or abortions)

     • Blood transfusions

     • Organ transplants...may have developed harmful antibodies without knowing it.

3. First-Time Mothers Aren’t Automatically Safe

   • Some women have naturally occurring antibodies (like anti-M or anti-Lea).

   • Even in a first pregnancy, these can pose risks.

     
     

How Is the IAT Done?

1. Blood Sample Collection – A simple blood draw from the mother's arm.

2. Lab Testing – The sample is mixed with test red blood cells to detect antibodies.

3. Antibody Identification – If positive, further testing determines which antibodies are present.

   
   

When Should It Be Done?

✔ First prenatal visit (for all pregnant women)

✔ 28 weeks (for Rh-negative women, along with RhoGAM)

✔ After delivery (if baby's blood type is incompatible)

Repeat testing may be needed if:

• The mother receives a blood transfusion during pregnancy

• There’s a history of unexplained fetal anemia or stillbirth

Why Is the IAT So Important?

The test helps prevent:🚨 Hemolytic Disease of the Fetus and Newborn (HDFN) – Where the baby’s red blood cells are destroyed🚨 Severe Anemia in the Baby – Can lead to heart failure (hydrops fetalis)🚨 Jaundice and Brain Damage (Kernicterus) – From high bilirubin levels

Benefits for the Mother

✔ Early detection of risks before they become dangerous

✔ Preventive treatment (like RhoGAM for Rh-negative women)

✔ Peace of mind knowing baby is protected

What If the IAT Is Positive?

If harmful antibodies are found:

1. Identify the specific antibody (anti-Kell, anti-Duffy, etc.)

2. Monitor the baby closely with:

   • Regular ultrasounds

   • Middle Cerebral Artery (MCA) Doppler to check for anemia

3. Plan for treatment, which may include:

   • Intrauterine blood transfusions (IUT)

   • Early delivery

   • Neonatal treatment (phototherapy or exchange transfusions)

   

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Key Takeaways

🔹 The IAT is NOT just for Rh-negative women – ALL pregnant women should be screened.

🔹 Minor blood group antibodies can be just as dangerous as Rh incompatibility.

🔹 Early testing saves lives by preventing severe complications.

💡 Action Step:

• Ask your doctor about the IAT at your first prenatal visit.

• Don’t assume you’re low-risk – even first-time moms need screening.

📢 Share this information! Many expecting parents don’t know how important this test is.