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Diet Soda May Be Linked to Preterm Birth

Reviewed by James Brann, M.D.

Artificially Sweetened Drinks Linked to Early Delivery

Learn about how diet soda may be associated with preterm dDelivery.

If you're a regular diet soda guzzler, you may want to switch to another type of drink during pregnancy. A new study published in a July 2010 issue of the American Journal of Clinical Nutrition suggests that drinking artificially sweetened soft drinks during pregnancy may increase your risk of preterm delivery.

Preterm delivery, or labor that happens before 37 weeks pregnant, is a serious pregnancy complication that occurs in 12 percent of all pregnancies in the United States every year. It can put your baby at higher risk of requiring hospitalization and suffering from long-term health problems. The earlier your baby is born, the more problems he or she faces. Infants who are born very early may suffer from brain problems, digestive problems, breathing problems, and even death within the first several days of life.

The cause of preterm labor and delivery is often unknown, but researchers have indicated that several factors can increase your risk. This includes:

  • Previous preterm delivery

  • Pregnant with twins or multiples

  • Uterine or cervical abnormalities, such as cervical insufficiency

  • Late or no prenatal care during pregnancy

  • Smoking, drinking alcohol, and abusing illegal drugs

  • Stress

  • Exposure to environmental pollutants

  • Medical conditions, such as urinary tract infections, diabetes, high blood pressure, preeclampsia, and clotting disorders.

  • Birth defects in the baby

  • Pregnant due to in vitro fertilization

  • Underweight before pregnancy

  • Obesity

The study, which was led by researchers in Denmark at the Statens Serum Institut, looked at the soft drink (both sugar-sweetened and artificially-sweetened) consumption of 59,334 Danish pregnant women and the instances of preterm labor and delivery.

The researchers found that pregnant women who drink diet drinks (both carbonated and non-carbonated) are at an increased risk of preterm delivery. In fact, the risk increases with the number of artificially sweetened soft drinks that you consume. When you consume at least one serving of an artificially sweetened (diet) soda every day, you are 38 percent more likely to deliver early (before 37 weeks pregnant). Once you increase your soda intake to four sodas a day, your risk of preterm delivery increases to around 80 percent!

The risk of preterm delivery is the same for both normal weight and overweight women. Interestingly, the researchers noticed that daily diet soda intake led to more early to moderate preterm delivery (before 34 weeks) than late preterm (34 to 36 weeks pregnant). A term pregnancy is between 37 weeks and 42 weeks pregnant.

There was no association between drinking sugar-sweetened soda and the risk of preterm delivery, leading the Danish researchers in this study to theorize that it may be the artificial sweetener itself that leads to preterm delivery. It's not the act of drinking soda.

The research study did not analyze any specific artificial sweeteners, noting that diet soft drinks combine many different sweeteners. Because most international brands use the artificial sweeteners aspartame (NutraSweet) and acesulfame potassium (Sunnet), it is assumed that one of these sweeteners may have affected pre-term delivery in this study.

This Danish study is one of the first to link preterm delivery with artificially sweeteners. Past studies that focused on artificial sweeteners and their effects on pregnancy have focused on its neurological and behavioral impact on your baby. According to the researchers, few studies in humans have examined the potential toxicity (or poisonous nature) of artificial sweeteners.

For example, aspartame breaks down into aspartic acid, phenylalanine, and methanol after it is digested. Methanol is considered toxic to humans, because it is oxidized into formaldehyde (which is considered a carcinogen, or cancer-causing substance) and then formic acid.

The researchers point out that previous studies on primates (apes, monkeys, etc.) showed that monkeys that were exposed low doses of methanol had shorter lengths of pregnancy, compared to the animals that were not exposed to methanol.

As a result, the researchers of this Danish note that further studies are needed to confirm their findings and the theories presented in this recent study.

If you are concerned about your risk of premature delivery, you may want to cut back on your diet soda intake, or eliminate this from your diet completely. Many sodas also contain caffeine, a substance that has been linked to miscarriage in the past. Although moderate caffeine consumption (under 200 mg a day, or equal to a 12-ounce cup of coffee every day) is generally considered safe, consuming over 200 mg every day can double your miscarriage rate.

Although giving up caffeine and soda during pregnancy may seem unbearable, especially if you love your diet soda or morning coffee, it may be the best for you and your baby. Plus, keeping caffeine out of your diet may help with your insomnia (a very common pregnancy symptom).

However, don't be scared about this new research. Keep in mind that this study is new and future studies may either refute (dispute) its findings or support it.

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