Caffeine During Pregnancy: A Stimulating Summary of the Latest Research

by Michele Brown,

High Test or Decaf?

regular or decaf?There is no question that many of us love our morning cups of coffee, or tea. Caffeine wakes us from our slumber and helps us become alert for the challenging day ahead. The true question, which is very important for a pregnant woman to understand is why, and how, caffeine affects the mother's body -- and the subsequent influence of that cup of coffee, tea or hot chocolate on her unborn child.

Products that contain caffeine, such as coffee, tea, and chocolate are amongst the most popular and widespread products consumed in the world. Its usage may date as far back as 3000 BC, in China. While caffeine is known to be a natural pesticide that paralyzes and kills insects feeding on certain plants, its sustained popularity stems from several unique physiologic and pharmacologic properties.

In other words, caffeine contains chemicals that have a profound stimulating influence on the nervous system, as well as many other human bodily functions.

What Does Caffeine Do?

Caffeine's stimulant properties may:

  • Affect the central nervous system leading to increased alertness and arousal
  • Cause an increased heart rate
  • Have a diuretic effect that may lead to increased urination
  • Affect the muscular system positively through increased coordination and ability to perform physical labor but may also affect the muscular system negatively in higher doses, as it can lead to tremors
  • Have mental effects which can increase short term memory but decrease long term memory
  • Increase the effectiveness of other drugs, such as headache medications, and can help overcome drowsiness from antihistamines.

What happens to the baby when a product containing caffeine is consumed?

Caffeine is absorbed by the stomach and small intestine within 45 minutes of ingestion. It crosses readily to the placenta, accumulating in both the fetus and amniotic fluid. It is metabolized three times more slowly in pregnant women compared to non-pregnant women, allowing for greater, and longer lasting, accumulation in the fetus.

Caffeine also significantly decreases blood flow in the placental villi, (small projections which help increase absorption of nutrients) through constriction of the vessels. Keep in mind that the fetus gets everything it needs from blood flow including nutrition, oxygenation, etc. and, if these vessels become constricted, the fetus gets less of everything needed for growth and development. Consequently, it is thought that maybe this constriction can possibly lead to reduced growth and can be associated with impaired development later on in life—or even stillbirth.

Considering the quantity of caffeine consumed, knowing whether caffeine is harmful in pregnancy is a major public health concern. Many studies have been written about the safety of caffeine in pregnancy most concluding that no malformations have been attributed to caffeine consumption and that most scientists believe that caffeine is not a teratogen (an agent or factor that causes malformations in an embryo) in humans.

However, concerns regarding harmful effects have stemmed from animal and human studies that have shown decreased intrauterine fetal growth, lower birth weights (less than 2500 grams), and skeletal abnormalities. (Vlajinac,1997;Caan, 1989). Other studies have shown no association between caffeine use and adverse outcomes in pregnancy. (Linn, 1982;Bech 2007, Clausson, 2000) Results of these kinds of studies are always questionable because many have been retrospective studies; those being studies that depend upon patient recollection, vary in the amounts of caffeine consumed, have differing sources of caffeine (coffee, tea, chocolate, medication), and have different methods of preparation and serving sizes.

Other studies have correlated specific quantities of caffeine consumed as being the determining factor of risk. (Fenster,1991)

It is known, however, that caffeine is readily transferred into human milk and therefore breast feeding mothers, who consume caffeine, may cause stimulatory effects in younger children.

In 1980, the United States Food and Drug Administration advised pregnant women to avoid caffeine containing foods and drugs, or use them sparingly.

The UK Food Standards Agency has recommended that women limit caffeine intake to under 200 mg of caffeine per day, which is equivalent to 2 cups of instant of coffee.

In Summary:

Most recent studies conclude that caffeine intake during pregnancy does not impose a major public health issue with regard to fetal health. However, because of the controversy that exists with the use of caffeine and impaired fetal growth in pregnancy, it is probably advisable to reduce the intake of caffeine during pregnancy to under 300 mg/day (3 cups of coffee) and encourage drinking decaffeinated coffee as a substitute.

Estimates of caffeine intake that might be helpful for pregnant women: (150 ml portion)

Coffee Tea Soft Drinks Cocoa
Brewed 115 mg Loose 39 mg 15 mg 4 mg
Boiled 90 mg Tea bags 39 mg    
Instant 60 mg Herbal 0 mg    

Dark roast has less caffeine compared to light roast because roasting reduces the caffeine content.

Tea generally contains more caffeine that coffee but is generally brewed much more weakly.

1 g of chocolate bar = 0.3 mg caffeine.

Most drugs contain 50–100 mg of caffeine per tablet.

Dr. Brown, founder of Beauté de Maman, is a board-certified member of the American College of Obstetrics and Gynecology, a member of the American Medical Association, the Fairfield County Medical Association, Yale Obstetrical and Gynecological Society and the Women's Medical Association of Fairfield County. She is a magna cum laude graduate of Tufts University, completed her medical training at George Washington University Medical Center and completed her internship and residency in obstetrics and gynecology at Yale-New Haven Hospital. Dr. Brown has a busy obstetrical practice in Stamford, Connecticut and, as a clinical attending, actively teaches residents from Stamford Hospital and medical students from Columbia Presbyterian Hospital in New York.

Copyright © Michele Brown. Permission to republish granted to Pregnancy.org, LLC.