NEW YORK (Reuters Health) - Women who have ever been around smokers regularly may have more difficulty getting pregnant than those who have not, a new study suggests. The findings, researchers say, offer one more reason for women to kick the smoking habit.

Studies have found that women who smoke raise their risk of a number of pregnancy complications, as well as their infants' risk of health problems. Less is known about the dangers of second-hand smoke, though some studies have linked exposure during pregnancy to an elevated risk of miscarriage.

In the new study, of more than 4,800 women, researchers found those who'd grown up with a parent who smoked were more likely to report they'd had difficulty becoming pregnant -- defined as having to try for more than 1 year.

In addition, women who'd been exposed to second-hand smoke in both childhood and adulthood were 39 percent more likely to have suffered a miscarriage or stillbirth, and 68 percent more likely to have had problems getting pregnant.

"These statistics are breathtaking and certainly (point) to yet another danger of second-hand smoke exposure," said lead researcher Luke J. Peppone at the University of Rochester, New York.

"We all know that cigarettes and second hand smoke are dangerous," he added. "Breathing the smoke has lasting effects, especially for women when they're ready for children."

Peppone and his colleagues at the University of Rochester in New York report their findings in the December 5 online issue of the journal Tobacco Control.

For the study, the researchers analyzed surveys from 4,804 women who'd visited the university's Roswell Park Cancer Institute between 1982 and 1998 for health screening or cancer treatment. All had been pregnant at least once in their lives.

Overall, Peppone's team found 11 percent of the women had difficulty becoming pregnant, while one third had a miscarriage or stillbirth.

The risk of these problems tended to climb in tandem with the number of hours per day that a woman was exposed to second-hand smoke -- a pattern that suggests a cause-effect relationship.

Second-hand smoke contains a host of toxic compounds that could potentially harm a woman's reproductive health, Peppone and his colleagues note. Tobacco toxins may damage cells' genetic material, interfere with conception, raise the risk of miscarriage, or inhibit the hormones needed for conception and a successful pregnancy.

SOURCE: Tobacco Control, online November 27, 2008.

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