Screens for: Neural tube defects like spina bifida. Can potentially screen Down syndrome as well.
Who does it: Blood draw is done by a nurse or lab tech.
How it is done: A needle is placed into your vein and blood is drawn to take to the lab. There are up to four substances checked: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), estriol and inhibin-A.
When is it done: Between 15-18 weeks for best results.
Accuracy: The more hormones used, the more accurate. It is important to point out that this test is a screening. If this test is positive it does not mean that your baby is suffering from one of these problems, just that further testing may be needed.
Risk to mom: Slight pain from needle stick, rare potential for infection at the site of the blood draw.
Risk to pregnancy/baby: None known.
Also known as the triple screen, quad screen or AFP.