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One-third of pregnancies may miscarry.

One-third of pregnancies may miscarry

A new study indicates 31 percent of all successful fertilizations end in miscarriages, two-thirds of which occur before a woman or her physician becomes aware of the pregnancy.

Using refined early detection methods, eight scientists from the National Institute of Environmental Sciences in Research Triangle Park, N.C., and the College of Physicians and Surgeons at Columbia University in New York City tested daily urine samples from 221 healthy women attempting to conceive. The women's ages ranged from 21 to 42. Over the course of the study, the researchers found 198 pregnancies by testing for the level of human chorionic gonadotropin (hCG), a hormone produced by an egg about one week after fertilization. The level of hCG in the urine and bloodstream is a standard indication of pregnancy.

"Most of these early pregnancy losses would not have been detectable by the less sensitive assay for hCG used in earlier studies," the researchers state in the July 28 NEW ENGLAND JOURNAL OF MEDICINE. However, two of the three previous studies by other groups using hCG to detect pregnancy actually yielded higher estimates of early miscarriage. "This difference may reflect a lack of specificity in the assays used in the other studies," suggest the authors of the recent report, saying the presence of a similar steroid hormone sometimes gives a false indication of pregnancy in less sensitive tests.

With a method of detecting pregnancy after one week, epidemiologists can more precisely follow the effects of certain environmental conditions, such as radiation or toxins, on pregnancy. "There is now a method for looking at the episode of early pregnancy," says Allen Wilcox, the study's principal author. "That period has always been a black box."

Almost all women who had miscarried showed signs of high fertility just after the loss, with one-third of them conceiving in the next menstrual cycle. Within two years, 95 percent of the miscarriage group had normal pregnancies, carried to term.

"Even when it fails, early pregnancy is apparently a positive sign that the stages of reproduction leading to implantation are correct," the researchers observe. They suggest rethinking the current clinical practice in which women are advised to resume birth control just after miscarriage to give the uterus time to recover.
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Author:Bell, Laura
Publication:Science News
Date:Aug 6, 1988
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