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RH-and Pregnant? New blood test may mean you don't need anteD




RH- and expecting? New blood test means may not need anteD

You can now know your baby's blood group before your baby is born by having a simple blood test during pregnancy!

The test is called Non Invasive Perinatal Testing (NIPT) for Fetal Genotyping and the result is 98% accurate. It is an important test for you to have if your blood type is RH- because it determines whether or not there is a risk to your baby in utero and to any future pregnancies and if you will need anteD during pregnancy to mitigate that risk.

A mother who is RH- will only require AnteD if her baby is RH+. This is to prevent series complications should mother and baby's bloods mix. If your baby is RH- (as is the case in just over a third of all RH- mothers) you will not need anteD. If your baby's blood group is unknown however care providers must assume that your baby is RH+ as a precautionary measure and will recommend that you have anteD.

Until recently there was no way of knowing baby's blood group during pregnancy. Baby's blood type could only be determined from a blood sample taken after birth either from the cord or directly from baby. Therefore all RH - mothers were given anteD, including those with blood type RH - who did not need it.

AnteD is a blood product derived from human plasma and so not without risks. The availability of Fetal Genotyping means that that thousands of mothers in Ireland who previously would have received anteD will now avoid having the injection unnecessary.

Some hospitals are offering this test to all RH- mothers as standard but it is not yet available in some regions. If your hospital does not offer fetal genotyping you may not be aware that it exists. But there are other options available to you. The test can be accessed privately in some hospitals or through Private Midwives Ireland.

What is Rh negative Blood group and why do we need anteD?

There are four blood types A, B, O and AB. In addition you will be either D (rhesus) positive or negative. What this means is that a substance called D antigen in your bloodstream is either present or absent respectively. About 15% of the population have Rh D negative blood.

During pregnancy and birth a mothers blood and that of her baby’s can mix. If a mother is RH negative and her baby is Rh positive their blood groups are incompatible. Should red blood cells from the D positive baby reach the blood stream of D negative mother, the mother’s immune system will recognize the D antigen on the surface of the baby’s cells as “foreign” and she will produce Anti D antibodies. This process is known as sensitization.

Mother and baby’s blood can mix at any time in pregnancy and particularly during:

  • vaginal bleed
  • Trauma or injury to the abdomen
  • Obstetric procedures which can disturb the placental bed such as Chorionic Villi Sampling (CVS) or External Cephalic Version (ECV)

When AntiD antibodies are present in a mothers blood they can cross into baby’s red blood cells causing anemia, jaundice and serious complications of preborn and new-born baby. This is called Haemolytic Disease of The Fetus and Newborn (HDFN).

AntiD antibodies also remain in the mothers circulations and can effect subsequent pregnancies.

When baby is rhesus negative baby does not have Rh D antigens, mother does not produce Ante D antibodies and antiD is not required.

Luckily anti D is an effective treatment in the prevention of HDFN. It prevents the process of sensitization by mopping up any of baby’s blood cells released into the mother’s bloodstream before mother's immune system can detect them. AnteD is derived from donated human blood products and is given by injection. It must be administered within 72 hours of any sensitizing event.

How to access the blood test

The Non Invasive Perinatal Testing (NIPT) for Fetal Genotyping is recommended by NICE guidelines. A simple blood test is collected from the mother any time from 11 weeks. Genotype RH+ will be accurate to 98% and Rh- has a margin of error of only 0.1%. Despite this small margin of error best practice is to recheck baby's blood group for 100% accuracy after baby is born either via cord bloods or blood taken directly from baby.

Mothers who are unable to access Fetal Genotyping through their local maternity services can now do so privately. I understand that some obstetric consultants are sending samples for processing to the UK. Private Midwives Ireland are also offering the service. The cost of the test is €85 for existing clients. Mothers who have not booked care with Private Midwives but who wish to have the test can do so by booking a single antenatal appointment with their local Private Midwife.

Fetal genotyping means the need for anti D injection may be eliminated in up to 38% of cases.

The availability of Fetal Genotyping potentially eliminates the need for thousands of women across the country to receive anteD. This is good news for the Health Service Executive as Anti D is expensive to produce, supplies are finite, and it requires stringent systems in place to administer. But perhaps more importantly it is great news for mums who not only have more choice and certainty regarding anti D, but will receive it only when there is a clear medical indication to do so.

Are you RH-

Did you know about Fetal Genotyping

Was the test available in your hospital and did the result mean you avoided having anteD

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