Screening of maternal serum for fetal Down's syndrome in the first trimester

Down's syndrome may be detected by maternal blood tests during the first trimester of pregnancy. Tests for this form of mental retardation are usually performed in the second trimester. Researchers performed blood tests and fetal chromosomal analysis in 4,412 older pregnant women. Forty-eight of 61 fetuses affected by Down's syndrome were detected by blood testing before 14 weeks gestation. Blood tests for low levels of pregnancy-associated protein A and elevated serum human chorionic gonadotropin (hCG), along with maternal age, detected Down's syndrome in about 60% of cases.