The presence of household chemicals in food packaging, upholstery and carpets may lower a woman's fertility, caution experts.
Researchers have found the first evidence that perfluorinated chemicals (PFCs) - chemicals that are widely used in everyday items such as pesticides, clothing and personal care products - may be associated with infertility in women.
The study published online in Europe's leading reproductive medicine journal Human Reproduction found that women who had higher levels of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in their blood took longer to become pregnant than women with lower levels.
The American researchers used data from the Danish National Birth Cohort to assess whether levels of PFOS and PFOA in pregnant women's plasma were associated with a longer time to pregnancy. A total of 1,240 women were included in their analyses.
Blood samples were taken at the time of the women's first antenatal visit (between 4-14 weeks into the pregnancy) so that concentrations of PFOS and PFOA could be measured.
The researchers also interviewed the women at around the 12th week of pregnancy to find out whether the pregnancy was planned or not and how long it took them to become pregnant.
Infertility was defined as a time to pregnancy of longer than 12 months or infertility treatment to establish the current pregnancy, and the results were adjusted for potential confounding factors such as age, lifestyle and socio-economic status.
The levels of PFOS in the women's plasma ranged from 6.4 nanograms per millilitre (ng/ml) to 106.7 ng/ml, and from less than 1 ng/ml to 41.5 ng/ml for PFOA.
The researchers divided the women's levels of PFOS/PFOA into four quartiles, and found that, compared with women with the lowest levels of exposure, the likelihood of
nfertility increased by 70-134 percent for women in the higher three quartiles of PFOS exposure and by 60-154 percent for women in the higher three quartiles of PFOA exposure.
Dr Chunyuan Fei, from the University of California in Los Angeles (UCLA), the study's first author, said: "PFOS and PFOA were considered to be biologically inactive, but recently animal studies have shown that these chemicals may have a variety of toxic effects on the liver, immune system and developmental and reproductive organs.
"Very few human studies have been done, but one of our earlier studies showed that PFOA, although not PFOS, may impair the growth of babies in the womb, and another two epidemiological studies linked PFOA and PFOS to impaired foetal growth."