Fruit of the Womb
Fruit of the Womb

Another Reader's Questions Regarding First Trimester Screening for Aneuploidy

Anonymous has left a new comment on your post "Abnormal First Trimester Screening Results":

I received my screening results and was given a 1:86 chance of having a baby with Down syndrome (trisomy 21). I am 35 years old. Only my hCG levels were elevated. My PAPP-A was 1.4 and the baby's NT (nuchal translucency) was 2.4mm which I was told was at the 90%ile for the size of the baby and anything above 95% is considered elevated. Given that I don't "fit the pattern" with elevated hCG, decreased PAPP-A and elevated NT- am I facing better odds that the baby is fine? Could my hCG levels be elevated "just because" that's how I am?

Kenneth F. Trofatter, Jr., MD, PhD said...

To Anonymous Sept 14: I had a similar query from a reader and responded to her on that post on July 17. The answer is basically the same. The odds are what they are, regardless of the combination of measurements, serologic markers, and demographic information that led to them! You have a 1 in 86 chance of having a baby with trisomy 21. (That is about twice your 'age alone' risk and probably a more reliable 'risk estimate' as well because it is derived from real numbers based on your pregnancy and not just from the population-based risk of women at your age). That also means you have a 85/86 chance the baby does not have trisomy 21.

The important questions you must ask yourself are "How do I feel about those odds? Do I need some more information? Do I want to find out for sure whether or not the baby has a chromosomal abnormality before the baby is delivered?" If you would prefer not to have an invasive study done at this time, there are other options to consider. You could have an early anatomic survey of the baby done by ultrasound at 16 weeks and possibly couple that with a maternal serum marker panel ("quad screen") which will give you another asssessment of "risk." Some laboratories will combine the first and second trimester data into a single 'integrated' risk assessment. And/or, you could have a 'genetic sonogram' done at 18-20 weeks. If that is completely normal, your a priori risk (based on the screening tests, not your age) for a baby with trisomy 21 can be reduced 60-90% depending on the experience of the ultrasonographer.

Thank you for reading and my best wished for your pregnancy.
Dr T
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