If you're hoping to become pregnant, you probably will want to lay off the fast food, at least if you would like to conceive sooner rather than later. A study finds that women who tend to eat fast food frequently take longer to conceive than women who have healthier diets, especially those who eat plenty of fresh fruit.

Over 5,500 women who were pregnant for the first time were asked at their first prenatal visit about their diets, particularly in the month leading up to conception. The researchers, midwives in the UK, Ireland, New Zealand and Australia, asked the mothers-to-be how often in the weeks before becoming pregnant they thought they had eaten fresh fruit, green leafy vegetables, fish, and any type of fast food like fried chicken, pizza, burgers or fries. The women were also queried as to how long it had taken them to become pregnant.

Eating few fruits and fast food frequently can double your risk of infertility. But — in case the thought has crossed your mind — neither a lousy diet nor eating fast food will prevent pregnancy.

About eight percent of the couples in the study took more than a year to conceive. These couples were considered to be infertile. As researchers looked at the differences in diet among women who had fertility problems, they found that in women who ate little fruit — reportedly eating it less than three times a month — the risk of infertility rose from eight percent to 12 percent. Women who ate fast food four or more times a week, had twice the risk of infertility, increasing from eight percent to 16 percent.

Conception was also slower among women who ate more fast food and less fruit. It took women nearly a month longer to conceive if they had eaten fast food four or more times a week, compared to women who never or rarely ate fast food. Women who ate fruit the least needed an additional two weeks on average to become pregnant compared to women who generally ate about three servings of fruit a day.

It was only fruit that affected fertility and the length of time to conceive. The amount of fish and green leafy vegetables eaten did not appear to have any effect on conception.

The findings show that a healthy diet reduces the time it takes to become pregnant, said Claire Roberts, the lead author and a research fellow at the University of Adelaide in Australia. Most of the women in the study had no history of infertility.

Women should pay attention to what they eat when planning a pregnancy to improve the chance of conceiving more quickly, according to Jessica Grieger, another researcher from the University of Adelaide.

And in case the thought has crossed your mind, the answer is no! Neither a lousy diet nor eating fast food will prevent pregnancy.

The study was published in Human Reproduction.