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Last Updated: Thursday, 20 January, 2005, 01:20 GMT
Test tube baby gets blood check
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Babies can inherit an incompatible blood match
Genetic screening has been used to ensure a test tube baby's blood was compatible with that of its mother.

The test, by Australian doctors, enabled a couple to have a healthy child who might otherwise have died.

The technique, pre-implantation genetic diagnosis, is already used to screen embryos for potentially fatal inherited diseases such as cystic fibrosis.

Its use to check the baby for rhesus disease is described in the Journal of the American Medical Association.

Dangerous mix

Rhesus disease is caused by the mother's immune system reacting against her baby's blood.

About 17% of pregnant women are at risk of having a rhesus baby.

The problem can arise when the mother's blood type is rhesus negative and the father's is rhesus positive.

PGD depends on going through IVF and then taking the chance that you will become pregnant
Professor Charles Rodeck of University College London

If the baby is also rhesus positive and its blood mixes with its mother's - mainly during labour - antibodies are produced to destroy the child's red blood cells.

It can lead to severe anaemia in the foetus, and stillbirth or death of the baby shortly after birth.

Many of these cases can be prevented simply by giving rhesus negative women an injection to stop any antibodies being produced.

It is also possible to treat any affected baby while still in the womb by giving a blood transfusion.

But there is still a significant death rate associated with the condition.

Dilemma

"A couple who have had a significantly affected pregnancy are faced with the dilemma of whether or not to attempt further pregnancies," said Dr Sean Seeho of the University of Sydney.

"And the tendency for rhesus disease to worsen with each subsequent rhesus-incompatible pregnancy plays a major part in the decision."

Such a situation faced the couple involved in the test tube baby's case. The screening was carried out in 2003.

There are possible financial barriers because it involves IVF
Lead researcher Dr Sean Seeho

Dr Seeho's team used pre-implantation genetic diagnosis (PGD) to select a rhesus negative embryo from among a number of embryos produced after the mother underwent IVF treatment.

They say this is the first reported case of an unaffected pregnancy using PGD to prevent rhesus disease.

Dr Seeho believes PGD is an option for couples who have had a previous severely affected pregnancy and the man's blood type, although classified as rhesus positive, is actually a mix of rhesus positive and negative.

But he warned that financial and technical barriers remained.

Professor Charles Rodeck of University College London suggested PGD would be appropriate for very few couples.

Of the 600,000 or more births in England and Wales each year, about 62,000 are rhesus positive babies born to a rhesus negative mother.

In up to 98% of cases the mother and baby can be successfully treated to avoid any complications


SEE ALSO:
3.4m for blood disorder baby
09 Dec 02 |  England


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