Mother Knows All
Next generation of prenatal tests finds clues to baby's health in mother's blood
For 9 months, doctors can at best make educated guesses about a growing fetus’ future as a healthy human. Those first fuzzy black-and-white ultrasound images can provide a mother with the peace of mind that she has a boy or girl with a beating heart, but many developmental maladies leave no visible fingerprint. Doctors can diagnose some genetic disorders by means of amniocentesis, in which they examine whole fetal cells extracted from the amniotic fluid that surrounds a baby in the womb. But the risk of complications from this invasive procedure, which requires inserting a long needle into a woman’s abdomen, can exceed the risk that something was wrong to begin with.
In the late 1990s, Dennis Lo, now at the Chinese University of Hong Kong, was studying a possible low-risk way to get a window on a fetus’ health by searching for fetal cells in pregnant women’s blood. But “the problem with fetal cells is that they are incredibly rare,” says Lo. One milliliter of a pregnant woman’s blood, which contains 6 million cells, might yield only one or two fetal cells.