The study may take up to 30 minutes. This screening test measures maternal serum alpha-fetoprotein along with the level of two pregnancy hormones called estriol and human chorionic gonadotropin. The blood test is done between the 15th and 20th weeks of pregnancy to screen for open neural tube defects and Down syndrome. The results usually are available within one week. An abnormal test simply means that additional testing is needed.
Ultrasound examination is usually the next step.
If the ultrasound study does not provide an explanation for the abnormal test, amniocentesis is recommended. Only 10 percent of women will have abnormal results, and one of these ten will have a fetus with a birth defect. All Rights Reserved. Please view our Disclaimer and Privacy Statement .