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Is Caffeine Harmful During Pregnancy?

written by: Terrie Schultz • edited by: Rhonda Callow • updated: 6/23/2010

Consuming high amounts of caffeine during pregnancy may increase the risks of low birth weight babies, premature labor, and miscarriage. Experts recommend keeping caffeine consumption to a minimum during pregnancy.

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    Effects of Caffeine

    Caffeine affects the body in a number of different ways. It acts as a stimulant as well as a diuretic. Some of the effects of caffeine include feeling edgy or nervous, insomnia, an increased heart rate, higher blood pressure, and more frequent urination, which can cause loss of body fluids and lead to dehydration. By stimulating the secretion of stomach acid, caffeine can cause indigestion and heartburn.

    Caffeine also constricts blood vessels, which can affect the flow of blood to the placenta. The caffeine consumed by the mother passes through the placenta and directly affects the baby, causing changes in sleep and movement patterns. The effect on the baby can persist even after the baby is born. Women who consumed an excess of 500 mg of caffeine daily while pregnant had babies with increased breathing and heart rates and who slept less during the first days after birth.

    Some studies suggest that consumption of more than 300 mg of caffeine a day can lead to an increased rate of miscarriage, premature labor, and babies with low birth weight. Consuming just 200 mg of caffeine a day (about one cup of coffee) can double the miscarriage rate. In one study, very large amounts of caffeine, the equivalent of eight cups of coffee per day, caused the risk of stillbirths to double. Other effects of caffeine in pregnancy include an increased risk of undescended testes in male babies.

    Women who are trying to conceive should also consider cutting back on their caffeine consumption, as some studies link caffeine to decreased fertility.

    In addition to caffeine, coffee and tea contain phenols, which are compounds that decrease the body's ability to absorb iron. This is another reason to cut down on these beverages during pregnancy.

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    How Much Caffeine is Safe?

    While it may not be necessary to completely eliminate all caffeine from the diet while pregnant, the March of Dimes Foundation recommends that expectant mothers and women trying to conceive limit the amount of caffeine they consume to less than 200 mg per day. Below is a list of how much caffeine is contained in common foods and beverages.

    Brewed coffee 8 oz. 102-200 mg

    Instant coffee 8 oz. 27-173 mg

    Black tea 8 oz. 40-120 mg

    Green tea 8 oz. 30-50 mg

    Cola 12 oz. 35-38 mg

    Hot cocoa 8 oz. 3-13 mg

    Mountain Dew 12 oz. 54 mg

    Dark chocolate 1.45 oz. bar 31 mg

    Milk chocolate 1.45 oz bar 11 mg

    Coffee ice cream 50-60 mg

    Caffeine is also found in some over-the-counter products such as pain relievers and allergy and cold remedies. Before you use these products, check the label to find out how much caffeine is contained per dose.