New research suggests that drinking lots of artificially sweetened beverages may be linked with an increased risk of premature births. "It may be non-optional for pregnant women to have high consumption of these types of products," Dr. Thorhallur I. Halldorsson of the Statens Serum Institut in Copenhagen, one of the researchers on the study, told Reuters Health.

"Diet" drinks are widely promoted as a healthy alternative to sugary sodas and juices, but Halldorsson and his colleagues note that there's been little research on the safety of regular consumption of artificial sweeteners in humans.

Soft drinks — both artificially sweetened and sugar sweetened — were recently linked to high blood pressure, the researchers add, which increases the risk of premature delivery. To investigate whether there might be a direct link, the researchers looked at nearly 60,000 Danish women who reported on their diet, including how many soft drinks they had each day, at around 25 weeks of pregnancy. Around 5 percent of women delivered their babies before 37 weeks.

Women who had at least one serving of artificially sweetened soda a day while they were pregnant were 38 percent more likely to deliver preterm than women who drank no diet soda at all, the researchers report in the American Journal of Clinical Nutrition.
Women who had at least four diet sodas a day were nearly 80 percent more likely to deliver preterm. The association was the same for normal-weight and overweight women.
The researchers did not report the actual risk of premature babies in each group. However, according to the March of Dimes, one in eight babies — or around 13 percent — is born too soon. This means that if drinking diet soda does indeed increase risk - which must first be confirmed by other research teams — a woman who drank at least one diet soda daily would have a 17 percent risk, while her risk would be around 22 percent if she drank four or more diet sodas.

Because only diet soda was linked to preterm delivery, not sugar-sweetened soda, the findings suggest that the artificial sweetener itself, not soda drinking, could account for the relationship, the researchers say. However, they add, other possible causes for the link can't be ruled out.

The researchers didn't look at specific artificial sweeteners, and Halldorsson noted that many beverages contain more than one of these chemicals. However, he and his colleagues say, there is indirect evidence linking the sweetener aspartame to preterm delivery in animals.

Aspartame breaks down into methanol and other substances in the body, which can in turn be converted to toxic substances such as formaldehyde and formic acid, the researchers explain. And studies in non-human primates have linked even very low exposure to methanol to shortened pregnancy and labor complications.
While pregnant women who consume soft drinks shouldn't be alarmed by the findings, Halldorsson said, "what we are seeing warrants further attention."


Am J Clin Nutr. 2010 Jun 30. 
Intake of artificially sweetened soft drinks and risk of preterm delivery: a prospective cohort study of 59,334 Danish pregnant women.
Halldorsson TI, Strøm M, Petersen SB, Olsen SF.
Centre for Fetal Programming, Division of Epidemiology, Statens Serum Institut, Copenhagen, Denmark, Reykjavik, Iceland.


BACKGROUND: Sugar-sweetened soft drinks have been linked to a number of adverse health outcomes such as high weight gain. Therefore, artificially sweetened soft drinks are often promoted as an alternative. However, the safety of artificial sweeteners has been disputed, and consequences of high intakes of artificial sweeteners for pregnant women have been minimally addressed.

OBJECTIVE: We examined the association between intakes of sugar-sweetened and artificially sweetened soft drinks and preterm delivery. DESIGN: We conducted prospective cohort analyses of 59,334 women from the Danish National Birth Cohort (1996-2002). Soft drink intake was assessed in midpregnancy by using a food-frequency questionnaire. Preterm delivery (<37 wk) was the primary outcome measure. Covariate information was assessed by telephone interviews.

RESULTS: There was an association between intake of artificially sweetened carbonated and noncarbonated soft drinks and an increased risk of preterm delivery (P for trend: </=0.001, both variables). In comparison with women with no intake of artificially sweetened carbonated soft drinks, the adjusted odds ratio for women who consumed >/=1 serving of artificially sweetened carbonated soft drinks/d was 1.38 (95% CI: 1.15, 1.65). The corresponding odds ratio for women who consumed >/=4 servings of artificially sweetened carbonated soft drinks/d was 1.78 (95% CI: 1.19, 2.66). The association was observed for normal-weight and overweight women. A stronger increase in risk was observed for early preterm and moderately preterm delivery than with late-preterm delivery. No association was observed for sugar-sweetened carbonated soft drinks (P for trend: 0.29) or for sugar-sweetened noncarbonated soft drinks (P for trend: 0.93).

CONCLUSIONS: Daily intake of artificially sweetened soft drinks may increase the risk of preterm delivery. Further studies are needed to reject or confirm these findings.