Food packaging, shampoo, clothes, and other household products contain chemicals that may make it harder for some women to get pregnant, suggests the first study on the subject.
It's still too early to recommend that women who want to conceive try to avoid these products, said lead researcher Chunyuan Fei, a Ph.D. student in epidemiology at the University of California, Los Angeles. But her results are concerning enough to warrant further work.
"This is quite a new topic and lots of things are unknown," Fei said. "Because these chemicals are widespread, I think it's important to conduct more study."
The chemicals Fei and colleagues looked at belong to a group called perfluorinated chemicals, or PFCs, which appear in a variety of common products, from upholstery to pesticides. In particular, the researchers focused on perfluorooctane sulfonate and perfluorooctanoate, which are respectively called PFOS and PFOA.
Studies have linked PFOS and PFOA to toxic effects in the livers, immune systems, and reproductive systems of animals. In people, Fei and colleagues previously found that women with many children had lower blood levels of PFOS and PFOA than did women with fewer children.
In turn, the scientists wondered if these chemicals might affect fertility. Eight percent of women in the United States have visited their doctors for infertility-related reasons, according to the Centers for Disease Control and Prevention.
To investigate, the team collected blood and surveyed more than 1,200 newly pregnant women who are taking part in the Danish National Birth Cohort, a long-term health study. All of the women had become pregnant on purpose.
About 30 percent of women tried for more than six months before conceiving, results showed. Half of those tried for more than a year.
There was an equally big range in chemical levels in the women's blood — with more than 40 times more PFOA in some women than others and more than 16 times more PFOS from the lowest to highest concentrations.
For analysis, the researchers divided the women into groups of high and low chemical levels. Their calculations showed that women with the most PFOS in their blood were up to 134 percent more likely to have needed six months or more to get pregnant. Women with the most PFOA were up to 154 percent more likely to have trouble conceiving.
The findings are important, said epidemiologist David Savitz, because PFOS and PFOA are virtually impossible to avoid. We all have at least low levels of them in our bodies. Yet, they haven't been studied extensively.
"That leaves them in the 'Who knows what we'll find' category," said Savitz, director of the Disease Prevention and Public Health Institute at Mount Sinai School of Medicine in New York.
But he's not ready to jump to conclusions until further research comes along to support or refute it.
"It's well done but it still kind of sits there more or less in isolation," he said, adding that many companies are in the process of phasing out PFOS and PFOA anyway. "I would certainly urge suspending judgment or making any sort of behavioral response other than staying tuned."