I recently asked an Ob/Genetics colleague if amniocenteses were vanishing in his region and he answered-“like the buffalo”! This should be an enormous concern to all of us involved in women’s health care.

The acceptance of genetic amniocentesis should be increasing.  I believe it is falling because women are being misinformed and misled toward accepting First Trimester Risk Estimation (by nuchal translucency measurement plus assay of B subunit hCG and Papp-A) or second trimester ultrasound as a substitute for an indicated genetic amniocentesis.  Patients and physicians need to understand that ultrasound and serum assays cannot diagnose or rule out any chromosome abnormality.  They are not diagnostic.

I applaud risk estimations (more correct than “screening”) in the first or second trimester to identify pregnancies which were not previously known to be at sufficient risk to offer diagnostic testing.   More couples may then benefit from prenatal diagnosis. The use of the term invasive testing for either CVS or amniocentesis should be abandoned as a prejudicial nudge against indicated diagnostic testing.

CVS is usually quoted as having a 1% risk of pregnancy loss by its strongest proponents.  That is a risk pregnant women may accept or decline.

Second trimester amniocentesis has for decades been misquoted as having a 1 in 200 risk of pregnancy loss.  It was reported at the December NIH anel that the federally funded FASTER Trial finds the risk of loss in multiple centers with multiple operators to be 1 in 1100 (0.09%)[1].  This is less than one in a thousand!

This extraordinary level of safety must, of necessity, change all discussions with patients regarding prenatal genetic diagnosis. It had previously been published that all pregnancies qualify by risk benefit analysis.[2].  Now it is even more true.

First trimester risk estimation may ultimately lead to detection of 80% of trisomy 21 and 80% of trisomy 18 after indicated diagnostic testing.  This is less than half of the chromosome abnormalities which may be present with advanced maternal age.  Second Trimester ultrasound (often called genetic sonogram by non-geneticists) will falsely reassure about half of chromosomally abnormal pregnancies.  The popularity of risk reduction for advanced maternal age is flawed by the fact that the presence of an abnormal finding is very important but the absence of an abnormal finding is not equally reassuring.  There is already a rising incidence of chromosomally abnormal newborns born to couples who were falsely reassured by screening.

It may be too early to officially propose eliminating all “screening” and simply offer amniocentesis to everyone. This would be the most cost effective and is the likely eventuality.  But for now, if we adopt the British 1^st trimester approach for low risk patients we should not apply it to advanced maternal age patients.  Any approach to avoid “the needle” eventually deprives the patient of the correct answer in half the abnormal pregnancies.  This popular but deleterious path should be abandoned.  That will automatically occur when patient autonomy is respected by giving true informed consent about risks, benefits, accuracy and limitations of screening and diagnosis.  Counseling and consent will be the basis of all liability questions.

I believe it is an error to dissuade a patient from amniocentesis.  That now includes even a low risk patient.   Risk estimation of any sort should not be held out as a replacement or even a logical alternative to amniocentesis.  This will be debated ad infinitum but it is actually no longer even worthy of discussion.  Amniocentesis should always be encouraged-never discouraged.

Please contact Dr. Henry's office at 303-399-5393 if you have any questions.  Ask to speak to a Genetic Counselor.