Women with higher levels of perfluorinated chemicals (PFCs) in their blood take longer to become pregnant, a new study says. Researchers from the University of California, Los Angeles took blood samples from 1,240 women at their first prenatal visit, and interviewed them about whether the pregnancy was planned and how long it took them to get pregnant, the BBC reports. They found the chance of infertility (taking over a year or IVF to get pregnant) was much higher for women with high levels of PFCs in their blood. These chemicals, which have been linked to organ damage in animals, are used because they’re resistant to heat, and repel water and oil. One of the UCLA researchers noted that earlier studies have suggested PFCs might harm a baby’s growth in the womb, adding that women with more PFCs in their blood tend to have irregular menstrual cycles, too. The study is published in the journal Human Reproduction.