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Caffeine Consumption in Pregnant Women and Its Effects on Infant Health


Sarah Russell

September 24, 2007



What does caffeine do to our bodies?


Caffeine stimulates the central nervous system by binding to receptors specific to adenosine, a neurotransmitter in the brain that causes drowsiness.  As a result, the receptors cannot detect the actual levels of adenosine, the inhibitory response of adenosine levels is no longer functional and the receptor speeds up significantly (except it is binding to caffeine).


This substitution sends messages to adrenal gland (via the pituitary gland), where it produces the “fight or flight” hormone epinephrine.  This causes:


-          Dilated pupils

-          Opening of bronchial tubes

-          Increase in heart rate

-          Higher blood pressure

-          Release of insulin into the blood stream from the liver

-          Tightened muscles

-          Higher metabolism





What does caffeine intake do during pregnancy?


Recent studies have shown that consuming more than 300 milligrams of caffeine a day will increase one’s chances of a miscarriage, and based on studies on animals, high levels of caffeine may also cause birth defects, preterm delivery, reduced fertility and low birth weight.


There is also a link between consuming even more caffeine (more than 500 mg a day) and faster heart and breathing rates in babies in the first few days after birth.


Caffeine passes through the placenta and is absorbed by the baby.  In pregnant women, caffeine is active in the body for up to 11 hours, but up to 100 hours in the fetus because the developing babies still lack the necessary enzymes to detoxify and break it down.

Is it safe to consume caffeine during pregnancy?

Although the affects of caffeine continue to be revaluated, physicians are now saying that it is safe to consume up to 300 mg a day.  However, the chemical processes of caffeine in the body do not change simply because of a moderate dosage.  Caffeine still has strong effects that can indirectly affect and complicate pregnancy.  The stimulant still causes high metabolism, headaches, insomnia, heartburn and dehydration, which can all affect the development of the baby.  Also, as the pregnancy process progresses, the slower women’s bodies break down caffeine, causing a higher and longer exposure of caffeine to the baby.

The presence of caffeine also tends to be overlooked in several foods, which inhibits people to be fully aware of their actual daily caffeine intake.  Although caffeine must be included in ingredient lists for soft drinks, they do not have to disclose how much caffeine they contain. In addition, Neither the presence nor amount of caffeine is indicated on most labels of tea, coffee, and foods made with those beverages, such as ice cream and yogurt. Here are some examples of how widely caffeine levels vary in certain foods:


One can never know exactly how much caffeine he or she is actually consuming, and therefore pregnant women should be extremely careful when determining how much caffeine they want to drink.



Coffee, 8oz drip

104-192 mg

Tea, 8oz brewed  


Iced Tea, 8 oz


Soft Drinks, 8 oz


Cocoa Beverage, 8oz 


Milk Chocolate, 1 oz


Dark Chocolate, 1 oz 


http://www.ameribev. org/index.aspx      

Intervention: How to reduce caffeine intake

Although a single caffeinated drink or serving of food will not make much of a difference to a baby’s health, there is always potential risk, especially in large amounts.  Cutting back on caffeine can be difficult because it is an addictive drug.  A few suggestions on reducing caffeine intake are:


What are the effects of caffeine consumption on birth weight?  Preterm birth?  Likelihood of a miscarriage?

What are the effects on fetal growth?

What are the confounding factors when testing effects of caffeine intake during pregnancy?

Are certain types of people (of a certain race, sex, lineage) who are more or less likely to be affected by maternal caffeine intake during pregnancy?

Does maternal caffeine intake have any long term effects on the child?

Research Studies:

Study 1:

The first study was called “High caffeine consumption in the third trimester of pregnancy: gender-specific effects on fetal growth.” Caffeine intake among mothers of small for gestational age (SGA) and of non SGA mothers was recorded over the course of three days in each trimester, with a sample size of approximately 1000 women.  The results of the experiment showed that an increased rate of SGA birth for boy infants when caffeine levels were high, but no change for girls.  These results “suggest that a high caffeine intake in the third trimester may be a risk factor for fetal growth retardation, in particular if the fetus is a boy.”


Study 2:

In this study, healthy who delivered after 37 weeks of gestation were randomly selected from a pool of 1966 and compared with 502 women who gave birth in under 37 weeks.  The results of this study showed an inverse correlation between coffee consumption and duration of pregnancy.  Still, with this association, low levels of coffee consumption has negligible effects. 


Study 3:

Infant pre-maturity and low birth weight are effects intrauterine growth retardation.  Two control groups of about 350 infants were set up, and caffeine consumption within the two groups was analyzed, with confounding factors, such as mother’s age, marital status, income, schooling and smoking, taken into account.  Caffeine consumption fell under two groups: greater and less than 300 mg per day.  The comparative results of the two groups showed no correlation to the level of maternal caffeine intake and rates of pre-maturity, low birth rate or intrauterine growth retardation.


Study 4:

Another study, performed at the Department of Epidemiology and Public Health at Yale University, also found insignificant evidence of links between maternal caffeine intake and intrauterine growth retardation.  In a study of 2714 women who delivered liveborn children, they consumed more than 300 mg per day for the first and seventh months of pregnancy.  There was minimal change, and therefore “provides evidence that antenatal caffeine consumption has no adverse effect on fetal growth.”


Study 5:

In a group of 1529 women, “linear and threshold effects of prenatal caffeine on pregnancy outcome and offspring development were examined in a cohort of approximately 500 offspring.”  After statistical adjustment of confounding factors, caffeine consumption levels were compared to height, weight, and circumference of the newborn’s head and an IQ test at age seven.  None of the comparisons validly correlated to prenatal caffeine exposure.  Thus, the long-term effects of caffeine consumption during pregnancy and practically nonexistent.




There were several other studies on the withdrawal, neurological, cardiovascular and developmental effects of caffeine consumption during pregnancy.  However, many of these studies did not have reliable evidence- the sample size was either too small, there were too many confounding factors, and the samples were not randomized.  This made research on these other potential effects more difficult, and lacking in conclusive evidence.


Based on the studies of effects of caffeine on preterm birth, low birth weight and intrauterine growth retardation, there is little to no causation.  This contradicts the popular and commonly published statement that consuming caffeine more than 300 mg a day is unsafe.


These studies, which are reliable and were well-performed,  may conclude that it is alright for pregnant women to drink higher levels of caffeine, there are still a myriad of cases that show that there are negative effects on infant health, even if these studies are not as scientifically sound.  Although it is important to find scientific truth on the matter, when it comes to the safety of something so vulnerable, it cannot hurt to be too cautious about the health of one’s baby.



Barr, H.M., Streissguth, A.P.  (1991). Caffeine use during pregnancy and child outcome:

a 7-year prospective study.  Neurotoxicology and teratology, 441-448.



Bicalho, G.G., Barros Filho Ade, A.  (2002).  Birthweight and caffeine consumption. 

Revista de saúde pública.  180-187.

Chiaffarino, F., Parazzini, F., Chatenoud, L., Ricci, E., Tozzi, L., Chiantera, V.,Maffioletti,           C., Fedele, L. (2006).  Coffee drinking and risk of preterm birth.  European Journal of Clinical Nutrition, 610-613.

Grosso, L.M., Rosenberg, K.D., Belanger, K., Saftlas, A.F., Leaderer, B., Bracken, M.B.  (

(2001).  Maternal caffeine intake and intrauterine growth retardation.  Epidemiology, 447-455.


Vik, T., Bakketeig, L.S., Trygg, K.U., Lund-Larsen, K., Jacobsen, G. (2003).  High

caffeine consumption in the third trimester of pregnancy: gender-specific effects on fetal growth.  Pediatric Perinat Epidemiology, 324-331.



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