Caffeine intake of 6 or more units per day during pregnancy is associated with impaired fetal length growth, according to the results of a cohort study reported online April 28 in the American Journal of Clinical Nutrition.
"Caffeine is a widely used and accepted pharmacologically active substance," write Rachel Bakker, from Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues from the Generation R Study. "The effect of caffeine intake during pregnancy on fetal growth and development is still unclear."
The goal of the study was to evaluate the associations of maternal caffeine intake from coffee and tea with fetal growth measured during each trimester of pregnancy and with the risks for adverse birth outcomes. From 2001 to 2005, a total of 7346 pregnant women in the Netherlands participated in a population-based prospective cohort study from early pregnancy onward.
Questionnaires were used to determine coffee and tea consumption in the first, second, and third trimesters. Serial ultrasound studies allowed determination of fetal growth characteristics, and hospital record review allowed determination of birth outcomes.
A regular serving of 125 mL of coffee in the Netherlands contains approximately 90 mg of caffeine (caffeinated), decaffeinated coffee contains 3 mg, and tea contains 45 mg per 125-mL serving. This was used as the standard for calculation of daily caffeine consumption. Each unit of caffeine exposure was based on 1 cup of coffee (90 mg of caffeine), and total caffeine intake was categorized as less than 2 units, 2 to 3.9 units, 4 to 5.9 units, and 6 or more units per day.
Caffeine consumption was not consistently associated with fetal head circumference or with estimated fetal weight in any trimester. In contrast, higher caffeine consumption was associated with smaller first-trimester crown-rump length, second- and third-trimester femur length, and birth length (P for trend < .05). The risk of having a small-for-gestational-age infant at birth was increased in mothers who consumed at least 6 caffeine units per day.
"Our results suggest that caffeine intake of ≥6 units/d during pregnancy is associated with impaired fetal length growth," the study authors write. "Caffeine exposure might preferentially adversely affect fetal skeletal growth. Further studies are needed to assess these associations in non-European populations and to assess the postnatal consequences."
Limitations of this study include observational design with possible residual confounding; and missing data on coffee and tea consumption, which may have led to loss of power.
"Length- or skeletal-related fetal growth characteristics seemed to be most consistently affected from the first trimester onward," the study authors conclude. "Further structural and functional studies are needed to assess organ-specific effects. Our results suggest that pregnant women should be advised to not consume ≥6 caffeine units (.540 mg) per day during pregnancy."
The Erasmus Medical Center Rotterdam, the Erasmus University Rotterdam, and the Netherlands Organization for Health Research and Development (ZonMw) financially supported the first phase of the Generation R Study. One of the study authors was supported by the Netherlands Organization for Health Research. Am J Clin Nutr. Published online April 28, 2010.