Common Chemicals May Affect Fertility

Jan. 28, 2009 -- Exposure to a type of chemical found in everyday items such as clothing, carpets, and food packaging may be adversely affecting women's fertility, delaying the time it takes them to become pregnant, according to a new study.

In the study, the higher the concentrations of these chemicals -- called perfluorinated chemicals (PFCs) -- in the women's blood samples, the more likely the women were to take more than 12 months to get pregnant.

"In our study, 75% of the women had concentrations that were associated with a longer waiting time [to pregnancy]," says study researcher Jorn Olsen, MD, PhD, professor and chair of epidemiology at the University of California School of Public Health. Olsen heads the Danish National Birth Cohort at the University of Aarhus in Denmark.

The study is published online in the journal Human Reproduction.

Meanwhile, representatives of manufacturers who use the chemicals say the study shows only an association, not a cause and effect, as Olsen also emphasizes. Major manufacturers who use the chemicals are participating in a voluntary phase-out of them.

Measuring PFC Levels

Olsen and his colleagues took blood samples from 1,240 women during their first pregnancy visit, when they were about four to 14 weeks pregnant, and measured concentrations of the chemicals. The researchers asked the women how long it took to become pregnant; they defined infertility as a "time to pregnancy" of longer than 12 months or the need for infertility treatment to become pregnant.

The women were part of the Danish National Birth Cohort, a study of women recruited from 1996 to 2002; most were 25 to 34. "We divided the women into equal size groups, lowest, higher, [even] higher, and highest values [of the chemicals]," Olsen tells WebMD. "We made the comparison between these groups'' in looking at the time to pregnancy.

They measured concentrations of two types of PFCs: PFOS (perfluorooctane sulfonate) and PFOAs (perfluorooctanoate). The chemicals are used to make such products as nonstick cookware and breathable clothing, among other items.

Compared to the women with the lowest levels of PFOS, women in the next three groups, with progressively higher levels of PFOS concentrations, had greater odds of taking more than 12 months to become pregnant. For instance, those in the group with the third highest concentration range of PFOS had a 2.34 times greater odds of taking more than 12 months to become pregnant than the women in the group with the lowest blood levels of the chemical.

The same was true for the concentrations of PFOAs, with women in the groups with the higher concentrations taking longer to become pregnant than women in the lowest concentration group. For instance, those with the next highest concentration of PFOAs had a two times greater odds of taking 12 months or more to become pregnant, compared to the women with the lowest concentrations of PFOAs.