How Often Do Women With Wacky Blood Numbers Have A Baby With Down Syndrome?

Posted on Tue, 16 Apr 2013

Question: Hi, With my wife's (24 year old, mother of 1 child) recent first trimester screening her Beta Free HCG number was 3.04 MoM and PAPP-a number was 0.41 MoM. Her ultrasound is more normal with Nuchal Translucency @1.5 and no other visible markers except probabably may be facial angle @87degrees. Combining all of this, we were given an odds of 1:504 for Trisomy 21. Doctors have asked us to wait for second trimester scanning to look for any markers before deciding to do further invasive diagnostic tests to confirm/deny downs syndrome. My question is, how often do women with whacky blood numbers have babies with Trisomy 21? Should we go for invasive tests to test for presence of downs? Please advise.

Answered by Dr. Dr. Rakhi Tayal (42 minutes later)

Hello,
Thanks for posting your query.

The Beta free HCG number at 3.04 Multiples of the Median (MoM) is at a slightly higher level than normal. Similarly, the PAPP number is also decreased.

The nuchal translucency at 1.5mm is normal for a first trimester scan.
The total risk factor calculated by the software program in your wife's case is 1 in 504 (less than 0.2%). This is an extremely low risk factor of having a baby with Down's syndrome.

The only way to be sure whether the fetus has a chromosomal abnormality is by having an invasive test such as an amniocentesis or chorionic villus sampling, but such tests carry a risk of causing a miscarriage. The risk of miscarriage can vary between 0.06%-1%.

It is best to wait until second trimester, go for a detailed scan, and assess the possibility of having a trisomy baby rather than going for an invasive test immediately.

Hope this answers your query. I will be glad to answer the follow up queries that you have.

Please accept my answer in case you do not have further queries.

Wishing you good health.

Regards.
Dr. Rakhi Tayal.

Above answer was peer-reviewed by : Dr. Shanthi.E

Follow up: Dr. Dr. Rakhi Tayal (32 minutes later)

Thanks for your reply doctor.

My wife's LMP was on 10 Dec 2012. We had the test on 11th March 2013. Her Free beta hcg was 80.2 ng/l and her PAPP-a number was 1000 UI/l. Do these numbers correlate to the numbers in MoM for the gestational age? Also, what would be the gestational age during the test?

Also, is the facial angle of 87 degrees normal?

Till what age of the fetus could we safely (legally or health-wise) decide to abort if it turns positive for downs after invasive testing?

Is it possible to completely rule out downs baby just by ultrasound alone?

Are there any non-invasive methods of detecting chromosomal anamolies like Materni21, Harmony, Verifi available in India?

Answered by Dr. Dr. Rakhi Tayal (23 minutes later)

Hello.
Thanks for writing again.

The numbers you have mentioned are calculated based on the mean values of the laboratory of normal pregnant women. It is the MoM values that are used by gynecologists for knowing the chances of any congenital malformations.

Frontomaxillary facial angle is normal upto 88.5 degrees.

After invasive testing, if it turns out to be positive for any malformations, you can opt for abortion until 20 weeks of pregnancy safely.

Ultrasound scan alone cannot completely rule out the possibility of Down's syndrome. The combination of serum tests and ultrasound scan only predict the likelihood of having any congenital defect.

There are no non-invasive tests to detect the chromosomal abnormalities that you have mentioned. For all these purposes, amniocentesis or chorionic villi sampling are the best tests.

Hope my answer is helpful.
Do accept my answer in case there are no further queries.
Regards

Note: Revert back with your gynae reports to get a clear medical analysis by our expert Gynecologic Oncologist. Click here.

Above answer was peer-reviewed by : Dr. Shanthi.E