Understanding Abnormal First Trimester Screening Results

Question
Hi

This is my second pregnancy and I am 41. I had a misscarriage with my first pg about 24 months ago.

I recently had my first trimester screening (12w1d). Results were not great and increased my odds for downs to 1:5.

My NT was 3.0 - they had a hard time getting it. My blood work was HCG 3.08 MoM but the weird part is my PAPP-A levels were perfectly normal.

I did have a vanishing twin but at 8 weeks the sak had shrunk quite a bit so the OB does not think that that would cause my HCG levels to be so high.

I am scheduled for an amnio on Jan 20 but I am very worried about taking the risk - I would not terminate for downs. But I can't go another 26 weeks without more definitive answers.

Are there any other conditions that could cause such high HCG with normal PAPP-A levels?

Thanks for any guidance you can give.

Val

Answer
Different labs have different criteria for HCG. My lab shows a range of HCG at 12 weeks to be 10,000-200,000. Usually, if you are not planning to terminate for any chromosomal abnormalities, we do not recommend the amnio. HOwever, if you want to know for sure, it is the only method that is 100% sure of the results. The risk of amniocentesis is small if it is done by a competent person and is done under sonographic control. At your age, I definitely would have the amniocentesis. (You will also find out the gender of the baby). Good Luck. PAPP-A is usually accurate.