Aug. 20, 2010 -- Pregnant women who drink artificially sweetened carbonated and noncarbonated soft drinks may be at increased risk for preterm delivery, a study shows.
But a spokeswoman for a beverage trade group says the study doesn't demonstrate cause and effect and unnecessarily alarms pregnant women. And the researchers themselves say more study is needed before firm conclusions can be reached.
The study is published in the September issue of the American Journal of Clinical Nutrition.
"We observed a positive association between the intake of artificially sweetened soft drinks and the risk of preterm delivery, [but] no association was observed for sugar-sweetened soft drinks," conclude study researchers, who were led by Thorhallur I. Halldorsson of the Centre for Fetal Programming at Statens Serum Institut in Copenhagen, Denmark.
Halldorsson says in an email to WebMD: “We see some indications suggesting that high intake of artificially sweetened soft drinks may be non-optimal for pregnant women but further research is needed to establish if that is truly the case. These soft drinks have been on the marked for around 30 years and one observational study is not enough to justify strong statements. We simply need more studies to confirm or reject our findings. It is, however, reasonable to encourage pregnant women to eat healthy and consume non-nutritive foods and beverages in moderation."
Maureen Storey, PhD, senior vice president of science policy for the American Beverage Association, a trade group in Washington, D.C, worries that the study is sending the wrong message. "This study raises unnecessary concern among pregnant women, the authors themselves acknowledge that their findings cannot demonstrate cause and effect," she says in a written statement. "In fact, they note that the alleged association between diet beverages and premature delivery was "primarily driven by medically induced delivery" and further research is needed."
Importantly, she adds, women who are pregnant "should seek out, consult with and heed the advice of their health care provider."
Causes of Preterm Delivery
Abdulla Al-Khan, MD, the director and chief of maternal and fetal medicine and surgery at Hackensack University Medical Center in New Jersey, is not in the habit of encouraging pregnant women to drink diet drinks. That said, he is also unsure that these beverages have a role in causing preterm labor or preterm delivery.
Exactly what causes preterm delivery is not fully understood, he says. "Genetics, uterine structure, fetal development, and infections all may play a role, so it is hard to say that diet drinks increase risk when we don't know 100% what is causing preterm delivery in the first place."
"You should limit your diet soda consumption as much as possible during pregnancy and go to natural products like fresh fruit or vegetable juice," he says. "Have no more than one can of diet soda every other day or every third day. Avoiding artificial sweetened drinks in pregnancy is sound advice, but it may not affect your risk of preterm labor and delivery."
The study results showed that pregnant women who drank one or more diet sodas per day were 38% more likely to deliver before 37 weeks than women who never drank artificially sweetened sodas. Those women who drank four or more diet sodas a day during pregnancy were 78% more likely to deliver early compared to women who did not drink diet sodas during pregnancy.
Since there was no increased risk seen among women who consumed sugar-sweetened drinks, the researchers suggest that it's the artificial sweetener, not soda drinking, that is responsible. Exactly how or why artificially sweetened soft drinks may increase risk of preterm delivery is not clear, but the researchers speculate that some of the sweetening ingredients may be broken down into substances that could increase this risk.
Researchers gathered information on consumption of soft drinks among 59,334 women in the Danish National Birth Cohort midway through their pregnancy. They controlled for some factors known to increase risk of preterm labor including advanced maternal age, smoking history, and weight before becoming pregnant.
Overall, 4.62% of women in the new study delivered prematurely, and 33.3% of these were "medically induced" preterm deliveries, meaning that the doctor induced preterm delivery to protect the health of the mother or baby. Drinking artificially sweetened diet soft drinks was more likely to increase risk of early preterm (before 32 weeks) and moderately preterm delivery than late-preterm delivery, the study showed.
Perspective of American Society for Nutrition
“These findings may be really important in terms of preventing premature births, especially those that are medically induced by a woman's health care provider," says Shelley McGuire, PhD, a spokeswoman for the American Society for Nutrition in a written statement.
"Certainly, until more experimental work is done, this study suggests that pregnant women should steer clear of artificially sweetened drinks," says McGuire, also an associate professor of nutrition at Washington State University in Pullman, Wash. "Pregnant women should be focusing more on nutrient-rich drinks anyway, like milk and fruit juices. And don't forget the water!”