Drinking more than one soda or sugar-sweetened beverage a day by either partner may decrease the chances of conceiving, warns a study.

The findings showed both female and male intake of sugar-sweetened beverages was associated with 20 per cent reduced fecundability -- the average monthly probability of conception. Females who consumed at least one soda per day had 25 per cent lower fecundability, while male consumption was associated with 33 per cent lower fecundability. "We found positive associations between intake of sugar-sweetened beverages and lower fertility, which were consistent after controlling for many other factors, including obesity, caffeine intake, alcohol, smoking, and overall diet quality," said lead author Elizabeth Hatch, Professor at the Boston University School of Public Health (BUSPH).

"Couples planning a pregnancy might consider limiting their consumption of these beverages, especially because they are also related to other adverse health effects," Hatch said, in a paper published in the journal Epidemiology. Intake of energy drinks was related to even larger reductions in fertility, although the results were based on small numbers of consumers. Little association was found between intake of fruit juice or diet soda and fertility.

Previous studies have linked the consumption of these beverages to weight gain, Type 2 diabetes, early menstruation and poor semen quality. For the new study, the team surveyed 3,828 women aged 21 to 45 living in the US or Canada and 1,045 of their male partners.