Understanding AFP Screening & Amniocentesis: What to Expect

Question
I am 5 months along in pregnancy and got a call the other day saying my bloodwork came back abnormal for the AFP screenig. And there is a problem they think with the chromosone 21 which could be the possibilty of down syndrome. I go on tuesday to get a ultrasound and amnosintesis done. But i am scared, do you have any information on it.

Answer
AFP (alpha feto protein) is a substance that is found in normal amounts in your blood. It is increased in situations where there are "neural tube defects", such as anencephaly, spina bifida, problems with the baby's brain and spinal cord, and it is decreased in Down's syndrome. However, the test is only a screen and is not an accurate determination because there is "overlap" with normal values. When we get an abnormal AFP, we follow it up with a sonogram and an amniocentesis. The amniocentesis is 100% accurate in showing any chromosomal abnormalities because some fluid, from around the fetus, is withdrawn and grown and a karyotype of chromosomes is prepared. This absolutely tells us if it is Trisomy-21 (Down's) or normal. A sonogram can also show "soft signs" of chromosomal abnormalities (nuchal fold transluscency, etc). Until you have the amniocentesis, don't worry. There are many errors with the AFP (wrong gestational age, overlap, etc). After the amniocentesis, you will know in around 10 days and will be given all of your options. Try not to be scared. Just follow the instructions of your doctor. Good Luck.