Caffeine Intake During Pregnancy May Be Associated With Risk of Smaller Babies
Caffeine is a commonly consumed stimulant. It is best associated with coffee but can also be found in soft drinks, teas, chocolates, and some over-the-counter medications. While the mother’s system may have adjusted to the effects, a developing baby’s system may be more vulnerable to caffeine. Previous studies have arrived at inconclusive results, but some have hinted that caffeine intake may be associated with increased risk of miscarriage and low birth weight.

Researchers in the United Kingdom (UK) wanted to review the risk of decreased baby growth from maternal caffeine consumption. They particularly noted when a baby’s growth was below what was expected for each stage of pregnancy. The study, published in the British Medical Journal , found that caffeine consumption may increase the risk of having a small baby.

About the Study
The cohort study recruited 2,635 women with low-risk pregnancy. The women were asked to report their caffeine intake from four weeks before conception through their pregnancy. Saliva samples were also taken to measure levels for caffeine, smoking, and alcohol. Smoking and alcohol are known to cause small babies.

After accounting for other toxins like alcohol and smoking, caffeine consumption throughout pregnancy was associated with higher risk of impaired growth. Compared to babies born to mothers who had less than 100 milligrams (mg) of caffeine daily (about an 8oz cup of coffee), babies born to mothers who consumed more than 100 mg of caffeine daily were:

  • 20g-70g (0.04 lbs-0.15 lbs) smaller in 1st trimester
  • 24g-74g (0.05 lbs-0.16 lbs) smaller in 2nd trimester
  • 66g-89g (0.14 lbs-0.19 lbs) smaller in 3rd trimester
The effects were consistent through all of the pregnancy trimesters. On average the small babies were about 60g-70g (0.13 lbs-0.15 lbs) behind their counterparts. Researchers also believe that the rate at which the mother metabolized the caffeine could play a role in the effect on the baby.

How Does This Affect You?
A cohort study has some limitations. It is an observation study , which means the researchers do not control all elements of the study. However, this study did take steps to account for other known causes of growth restriction like alcohol and smoking. It also took the further step of testing the women’s caffeine levels through saliva instead of relying solely on self-report. Previous studies may have only relied on a report of coffee consumption. In the UK study, 60% of participants received the majority of caffeine from tea.

Although some studies have conflicting results of caffeine’s true effect, all agree caffeine is not a necessary nutrient. It is best to reduce or eliminate caffeine from your diet before conception or during the pregnancy. Read labels and know what items may contain caffeine. Caffeine can now be found in items such as water, ice cream, and juices.

American Congress of Obstetricians and Gynecologists

National Women’s Health Resource Center

CARE study group. Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study. BMJ . 2008;337:a2332.

Last Reviewed December 2008

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