It was found that those who drank one serving per day of artificially sweetened fizzy drink were 38% more likely to give birth before 37 weeks gestation, and those who consumed four servings a day were 78% more likely to have their baby prematurely.

The effect was weaker for still artificially soft drinks, and there was no link between premature birth and sugar-sweetened drinks, they said.

It is thought the artificial sweeteners are broken down in the body into chemicals which may change the womb, the researchers said.

The study was published in the American Journal of Clinical Nutrition.

Dr. Shelley McGuire, spokesman for the American Society of Nutrition, said, "These findings may be really important in terms of preventing premature births, especially those that are medically induced by a woman's healthcare provider.

"Certainly, until more experimental work is done, this study suggests that pregnant women should steer clear of artificially sweetened drinks. Quite frankly, pregnant women should be focusing more on nutrient-rich drinks anyway, like milk and fruit juices, and don't forget the water."

The study conducted by Thorahallur Halldorsson, of the Statens Serum Institut in Copenhagen, did not examine which artificial sweeteners were contained in the drinks.

From the August 30, 2010, Prepared Foods E-dition