Women who eat a lot of fast food and little or no fruit may take longer to get pregnant, the results of a new international study involving Irish women indicate.

The findings also suggest that these women are less likely to conceive within one year.

The study involved over 5,500 women in Ireland, the UK, Australia and New Zealand, who were having babies for the first time. All were interviewed by research midwives during their first antenatal visit, at 14-16 weeks gestation.

Information about the time it had taken to get pregnant, along with the women's diets in the month before conception, was collected.

The researchers found that compared to women who ate three or more portions of fruit in the month before conception, those who ate fruit less than one to three times a month took around two weeks longer to become pregnant.

Women who ate fast food four or more times a week took nearly a month longer to get pregnant than women who never or rarely ate this type of food.

Fast food included pizza, burgers, fried chicken and chips that were bought from takeaway or fast food outlets. Fast foods eaten at home, for example those bought in supermarkets, were not included in the study.

Meanwhile, the researchers also looked closely at couples classed as infertile, i.e. those taking longer than a year to conceive. Some 8% of couples were classified as infertile in this study. However, among women with the lowest intake of fruit, the risk of infertility increased from 8% to 12%.

Among those who consumed fast food at least four times a week, the risk of infertility increased from 8% to 16%.

"The findings show that eating a good quality diet that includes fruit and minimising fast food consumption improves fertility and reduces the time it takes to get pregnant," commented the lead researcher, Prof Claire Roberts, of the University of Adelaide in Australia.

The study took into account other factors which can increase the risk of infertility, such as body mass index (BMI), maternal age and smoking.

"As diet is a modifiable factor, our findings underscore the importance of considering preconception diet to support timely conception for women planning pregnancy," the researchers added.

Details of these findings are published in the journal, Human Reproduction.