Drinking one or more sugar-sweetened drink a day -- by either partner -- could reduce the chance of getting pregnant by 20%, on average, according to an American study published in the journal Epidemiology.

Couples trying to conceive may want to consider curbing their intake of sugar-sweetened drinks in order to boost their chances of getting pregnant -- as well as limiting other adverse health effects -- concludes a study that followed 3,828 women in the USA and Canada and 1,045 of their male partners.

After taking into account other factors affecting fertility, such as obesity, caffeine intake, alcohol intake, smoking and diet quality, researchers at Boston University School of Public Health found positive associations between intake of sugar-sweetened drinks and lower fertility.

Study participants, aged 21 to 45, filled out an initial comprehensive questionnaire on their medical history, lifestyle factors and diet, then completed follow-up questionnaires every two months for up to 12 months or until they became pregnant.

The researchers found that both female and male intake of sugar-sweetened beverages was associated with 20% reduced fecundability, defined as the average monthly probability of conception.

According to the study, drinking one soda per day was associated with 25% reduced fecundability in women and 33% lower fecundability in men.

The study also highlights a link between energy drinks and even greater reductions in fecundability, although these results were based on small numbers of consumers.

Little association was found between intake of fruit juices or diet sodas and fertility.

Previous studies have found that drinking too many sugary drinks can lead to weight gain, diabetes, the early onset of periods and poor sperm quality.

"Given the high levels of sugar-sweetened beverages consumed by reproductive-aged couples in North America, these findings could have important public health implications," the authors conclude.