Chemicals commonly found in food packaging, upholstery and carpets may be damaging women's fertility, say US scientists.
A study published in the journal Human Reproduction measured levels of perfluorinated chemicals (PFCs) in the blood of 1,240 women.
Those with higher levels were more likely to take longer to become pregnant.
UK experts said more research was needed to confirm a link.
PFCs are useful in industry because they are resistant to heat, and have the ability to repel water and oil.
However, high concentrations have been linked to organ damage in animals, and the chemicals have the ability to persist for long periods in the body.
The researchers, from the University of California in Los Angeles, analysed blood samples taken at the time of the woman's first antenatal visit, then interviewed the women about whether the pregnancy was planned, and how long it had taken them to get pregnant.
The levels of the chemicals varied from 6.4 nanograms per millilitre of blood - a nanogram is a billionth of a gram - to 106.4 nanograms per ml.
When the group of women were divided into four groups depending on these levels, they found that, compared to women in the group with the lowest readings, the likelihood of infertility - taking more than a year or IVF to get pregnant - was significantly higher for women with higher levels of PFCs in their bloodstream.
Dr Chunyuan Fei, one of the researchers, said that earlier studies had suggested that PFCs might impair the growth of babies in the womb.
She said that more women in the groups with higher exposure to PFCs had problems with irregular menstrual cycles , which might suggest that interference with hormones was the reason.
Professor Jorn Olsen, who led the study, said that the team were now waiting for further studies to confirm the link between fertility problems and PFCs.
Tony Rutherford, chairman of the British Fertility Society, said that the findings were "interesting".
"This research shows a tenuous link in the delay to conception in women with the highest levels of two commonly-used perfluorinated chemicals.
"It is an important finding and certainly warrants further detailed research, particularly in those trying for a family.
"The study emphasises the importance of remaining vigilant to potential environmental factors that may impact on fertility."