Down's screening a few months pregnant

Down's screening can be considered between 15 and 20 weeks of pregnancy, preferably between 16 and 18 weeks. It can be done for pregnant women under 30 years of age. Down's screening can be done by examining the pregnant woman's blood and then taking the maternal serum for alpha fetoprotein and chorionic gonadotropin, free estriol, and then checking its concentration. Down's screening is an indicator of high or marginal risk before deciding whether to proceed with further testing.