For the study, which was published Friday in the peer-reviewed medical journal Human Reproduction, researchers analyzed diets of 5,598 women in Australia, New Zealand, the U.K. and Ireland.
The team found that women who eat fast-food four or more times a week took nearly a month longer to become pregnant.
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Fast-food was defined as items bought from fast-food restaurants and did not include items bought from supermarkets, such as pizza.
Meaning that overall, fast-food consumption might have been underreported, researchers said.
Researchers determined women who ate the least amount of fruit increased their risk of infertility from 8% to 12% and women who ate fast food four or more times a week increased their risk from 8% to 16%. Infertility is defined as not being able to get pregnant after one year, WFAA reports.
"We recommend that women who want to become pregnant should align their dietary intakes towards national dietary recommendations for pregnancy," first author Jessica Grieger said in a statement. "Our data shows that frequent consumption of fast foods delays time to pregnancy."
Eating green leafy vegetables and fish did not seem to affect time conceiving.