A survey of 5,598 women found those who ate fast food four or more times a week took nearly a month longer to get pregnant than those who never or rarely ate it.
Regular junk food eaters were also less likely to conceive within a year, the report in Human Reproduction found.
Lower intakes of fruit and higher intakes of fast food were both associated with modest increases in TTP and infertility.
A report on this study carried by the BBC, says that women in Australia, New Zealand, the UK and Ireland were quizzed about what they had eaten in the month before they became pregnant with their first child
Researchers found the women who had eaten fruit less than one to three times a month took on average half a month longer to become pregnant than those who had eaten it three or more times a day.
They also calculate that the women with the lowest intake of fruit had a 12% risk of having been unable to conceive within a year, while this was 16% for those who had eaten fast food four or more times a week.
This compared with a risk of 8% in the group as a whole.
Midwives visited the women when they were about 14-16 weeks pregnant and asked them how often they ate fruit, green leafy vegetables and fish, as well as foods, such as burgers, pizza, fried chicken and chips, from fast food outlets.