Friday, November 08, 2013

Chromosomal studies of the fetus after a miscarriage are a waste of money

A miscarriage is a heartbreaking event and the one thing the patient wants to know is – Why did the miscarriage happen ? Did I do something wrong ? And what can we do to prevent this from happening again ?

This is one of the reasons why a lot of doctors will send the fetus ( products of conception, POC) for genetic testing – either FISH or karyotyping or CGH. These are expensive tests, and I think many doctors do this as a knee jerk reflex – doctors like doing tests in order to make a diagnosis , and because patients demand
answers . ( Some do it because they make a lot of money by ordering the test !)

I think this test is pointless for most patients . We already know that the commonest reason for miscarriages (  more than 60 to 70% of the time ) is a genetic problem with the fetus, and this is Nature’s defense mechanism, to prevent the birth of an abnormal baby. While these defects are often random, they are commoner in older women. This is because the eggs of older women have more genetic abnormalities, because they have “aged” and have genetic defects, which cannot be screened for. This is why there’s no point in doing the test for an individual patient – it does not add any value to their life !

Please remember that genetic testing technology today is quite crude – it only allows us to count the number of chromosomes ; and to check their shape. Now, even if the test is result is abnormal, it only allows us to tell the patient that it was this genetic abnormality ( known as an aneuploidy) which caused the miscarriage ( something which we could have guessed even before doing the test anyway). Even worse, this knowledge does not really help the patient, because she wants to know what she can do to prevent the problem from recurring in her next pregnancy. However, because these are random errors, there is precious little we can do !

Also, just because the genetic test results  are normal does NOT mean the fetus is actually genetically normal. All it means is that the number of chromosomes the fetus had was normal ( euploid) . Now, there are many lethal genetic abnormalities which can cause a miscarriage, which we cannot pinpoint with our tests today.  This is not something which a lot of patients seem to understand – and even worse, most doctors don't seem to understand this basic fact either !

It’s a shame that we keep on mindlessly wasting a lot of money on these tests. While these tests may be useful for clinical research, they do not provide any useful clinical actionable information for the individual patient.

The only exception would be the couple where the baby has a genetic problem because of a chromosomal error in the parents ( one of whom is a translocation carrier). However, it’s easy enough to make this diagnosis by testing the chromosomes of the parents by doing a simple blood test – something which is much easier and less expensive than testing the chromosomes of the fetus.

Sadly, most gynecologists are pretty clueless about the limited value of these tests , because they don't understand much about genetics . They are quite happy to mindlessly tick off the box in the pathology form so kindly provided by the testing center , without thinking about whether the results will be of any use to their patient.

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