Down Detection; November 1998; Scientific American Magazine; by Ezzell; 2 Page(s)
Adrugstore urine test indicates to a 38-year-old woman that she is pregnant. After examining her and taking her history, her gynecologist tells her that she is roughly 10 weeks into the pregnancy. Although the woman is elated, she is also worried about Down syndrome, a form of mental retardation caused by an extra copy of chromosome 21 that occurs more often in the offspring of women older than 35. She and her husband have decided that they would opt for abortion if they conceive a fetus with the disorder. Her doctor says blood tests can determine whether the fetus has Down syndrome but only between weeks 16 and 18 of gestation--during the second trimester. That means the woman might face an abortion in the fifth month, which is particularly traumatic because such late abortions usually involve inducing labor and delivering the fetus.
The above scenario occurs hundreds of thousands of times every year in the U.S. alone. But researchers are now evaluating whether a suite of blood tests-- one of them new--can be combined with a novel ultrasound technique to detect Down syndrome reliably in fetuses as early as 10 weeks after conception.