Science / Medicine : Most Miscarriages Are Early, Undetected

A new test reveals that most miscarriages happen during the first month of pregnancy, long before women even realize that conception has occurred.

“We can say that the majority of early pregnancy loss appears to be unrecognized,” said Dr. Allen J. Wilcox of Research Triangle Park, N.C., who directed the study.

His work, published in the New England Journal of Medicine, suggests that 22% of all pregnancies end spontaneously in the first month, before women know they are pregnant. Another 9% result in miscarriages after the pregnancy becomes apparent.

Wilcox said the body probably rejects fetuses because they are defective. When researchers study later miscarriages in which fetal tissue is recovered, they find that half show gross genetic abnormalities.

The study was conducted on 221 healthy young women who had decided to stop using birth control and get pregnant. The researchers collected urine and checked it for traces of human chorionic gonadotropin, a hormone produced by the fetus.