... If there's a baby to bring up.

...If there's a baby to bring up

Home pregnancy tests are touted as a way for a woman to learn, quickly and reliably, whether she is pregnant. Companies marketing the tests claim up to 99 percent accuracy, as early as six to nine days after a missed period. But are the tests as reliable as they claim?

According to an article in the May AMERICAN JOURNAL OF PUBLIC HEALTH, those statistics are too good to be true. Instead, Mary Doshi of Marquette University in Milwaukee reports that in a study of 109 women whose menstrual periods were overdue by six to 20 days, three brands of home pregnancy tests had an average accuracy of 77 percent. When the kits were used before the 10th day after the missed period, the average accuracy of the results dropped to 66 percent. Negative test results were less reliable than positive results.

All of the investigated kits (Daisy 2, e.p.t. and Answer) reply on an antibody reaction to a hormone released during pregnancy. According to Doshi, the inaccuracy of early tests has two causes: The kits aren't sensitive enough to pick up the small amounts of hormone present early in pregnancy; and women using them aren't experienced enough to interpret borderline results or to avoid minor procedural errors that might be critical when hormone levels are low.

Women should wait at least 10 days after a missed period before using a test of this sort, Doshi says. "The companies are competing, trying to decrease the days" a woman needs to wait before testing, she says. "My study says it should be the opposite: They definitely should increase the days, at least with the sensitivity of the reagents they've got now."

A spokesperson for Carter-Wallace, Inc., manufacturer of Answer, says, "The company feels very strongly about their own testing procedures and their products. They stand behind them."