Understanding AFP Test Results & Down Syndrome Risk: A Doctor's Explanation

Question
Hi Doc,

My wife ObGyn office took blood samples to test the AFP and after few days they called us and said AFP levels are at high risk range of 1 in 170 risk of Down's Syndrome. They referred us to prenatologist and we went for Ultrasound 2 scanning and that doctor said they didn't see any signs of DS in the baby and he moved the risk level to 1 in 340 said low risk range. Prenatologist also aksed us to come back in 3 weeks for one more Ultrasound 2 scan saying baby is only 17 weeks age and it should be atleast 20 weeks for clear picture.

With the 1 in 340 risk range is it necessary to go for Amniocentasis for my wife? We are worrying that we might lose our baby because of this.

Thansks in advance.

Rod Bobse  

Answer
How old is your wife? At the age of 35, the risk of Down Syndrome is 1 in 350 pregnancies. At the age of 30, it is around 1 in 2700. At the age of 40 it is 1 in 100. The AFP is merely a screening test and if the results show an increased risk, we do a sonogram. If the sonogram showed no "soft" signs of DS, and they lowered the risk to 1 in 340, that is pretty good odds. Of course, if you had an amniocentesis, you would know 100% of the time.  The risk of miscarriage from the procedure of amniocentesis is 1 in 400 procedures. You have to decide what you want to do.