Studies On Caffeine & Pregnancy

You need to start making health decisions for two once you become pregnant. You may already know that drinking alcohol and smoking can harm your growing baby, but seemingly innocent habits may also be dangerous. For instance, if you typically enjoy a daily pick-me-up from coffee or soda, you may need to cut back on caffeine to reduce potential risks to your baby.

The Physiology

Caffeine's stimulant effect causes your heart rate and blood pressure to go up. Both of these conditions can increase your risk of pregnancy complications, according to the American Pregnancy Association. Caffeine is also a diuretic, meaning it causes you to urinate more frequently, which can reduce the amount of nutrition your baby receives from your body. Additionally, caffeine can prevent your absorbing enough iron and calcium from foods, which may impede your baby's development. Caffeine can directly affect your developing baby because it crosses through the placenta to the fetus. While your body may be able to tolerate your typical daily caffeine consumption, your fetus's still-developing metabolism can't completely metabolize the caffeine. Therefore, the fetus is susceptible to disrupted sleep patterns and greater health risks such as malnutrition.

Smaller Baby

According to a 2010 study of more than 7,000 pregnant women in the Netherlands, published in the "American Journal of Clinical Nutrition," women who drank at least 6 daily cups of caffeinated coffee -- at least 540 mg of caffeine -- were likely to have fetuses that didn't grow as long during each trimester and babies that were born at a smaller length compared with babies born to women who didn't drink any caffeine during their pregnancies. The same women who drank at least 6 cups of coffee were more likely to give birth to babies considered small for their gestational age.

Miscarriage Risks

In a 2008 study in the "American Journal of Obstetrics & Gynecology," researchers found that women who consumed under 200 mg of caffeine each day in early pregnancy were at a 40 percent higher risk of miscarrying than women who reported drinking no caffeine. Women who drank over 200 mg of caffeine each day were about twice as likely to miscarry as women who didn't consume any caffeine. Conversely, a 2008 study in "Epidemiology" found no connection between drinking 2 or fewer cups of coffee per day and increased risk of miscarriage.

Potential for Stillbirth

According to a 2003 Danish study published in the "British Medical Journal," women who drank 4 to 7 cups of coffee each day were slightly more likely to have a stillborn baby than women who didn't consume coffee. Women who drank at least 8 cups of coffee each day were more than twice as likely to have a stillbirth as women who didn't drink any coffee. The authors of the study concluded that drinking coffee during pregnancy was "associated" with -- not a cause of -- an increased risk of stillbirth but not with infant death during the first year of life.

Making a Decision

If you want to continue consuming some caffeine during your pregnancy, the March of Dimes recommends limiting your intake to no more than about 200 mg per day. The potential health risks of drinking caffeine aren't limited to coffee consumption, so be aware of how much caffeine is in other drinks and foods you consume. One 8 oz. cup of brewed coffee contains about 137 mg of caffeine, one 8 oz. cup of brewed tea contains about 48 mg, a 12 oz. can of cola contains about 37 mg and 1 packet of hot cocoa mix contains about 8 to 12 mg.