When do doctors test the fetus forr abnormalities?

At 12, 16 or 20 week: There are different ways to test for abnormalities and no one test can find all the problems. At 12 weeks a first screen can test for downs syndrome. At 16 weeks a quad screen or an amniocentesis can test for downs syndrome, abdominal wall defects and spine defects. At 19-20 weeks an ultrasound will look for other abnormalities. You should talk to your doctor about which ones are right for you.

Blood sonogram: blood for alfa feto protein sonogram amniocentesis for chromosomal problems