David Brill
Consuming caffeine during pregnancy can significantly increase the risk of fetal growth restriction, according to one of the largest and most comprehensive studies to weigh in on a notoriously inconclusive debate.
Pregnant women are typically advised to reduce their caffeine intake as a sensible precaution, but research findings have been inconsistent and a definitive link to birth defects has remained elusive.
The new study, which claims to be the first to give a “true picture” of caffeine intake in pregnancy, found that the association was significant at all levels of consumption and continued throughout pregnancy.
The size of the effect is similar to that seen for alcohol consumption, the UK researchers reported in the British Medical Journal. [2008 337:a2332] They recruited 2,635 low-risk women at 8 to 12 weeks of pregnancy and followed them up until birth.
An intake of more than 200 mg/day of caffeine was linked to an average birth weight reduction of up to 70g (P = 0.004) and increased the odds ratio for having a growth restricted baby to 1.5, as compared to an intake of below 100 mg/day (P = 0.02).
Dr. Shephali Tagore, an associate consultant in the department of maternal fetal medicine at KK Women’s and Children’s Hospital, Singapore, said the study confirms that the advice to reduce caffeine intake before and during pregnancy is appropriate.
“While previous studies have suggested a risk, this study group has objectively quantified caffeine from all known sources. This is a major strength of the study. They have found a dose-response relationship, showing that increasing caffeine intake was associated with increasing risk of fetal growth restriction,” she said.
Tagore added, however, that it is difficult to draw firm conclusions from the paper since there was no control group of women who did not consume any caffeine during pregnancy,
Previous studies have overestimated the impact of tea and coffee and relied too heavily on retrospective recall of caffeine consumption, according to the authors, who took a more thorough approach by using a comprehensive questionnaire which was validated against food diaries and saliva samples.
They found that only 14 percent of the women’s caffeine intake came from coffee. Tea was the major source, comprising 62 percent of intake, with cola drinks and chocolate contributing 12 and 8 percent respectively.
“We believe that, for the first time, this reflects a true picture of total caffeine intake by women during pregnancy,” they wrote. “Our findings emphasize the weakness of studies where caffeine intake was equated to that of coffee alone.”
Caffeine is absorbed rapidly and can cross the placenta freely. The main enzyme for breaking down the compound, however, is not found in the placenta or fetus so exposure depends largely on maternal metabolism.
To investigate whether individual metabolic differences affected fetal growth the researchers also measured the half-life of caffeine in the women’s saliva. The association with fetal growth restriction was strongest in women who had the fastest caffeine clearance but this result did not reach significance (P=0.06).
Caffeine consumption has also been linked to miscarriage. A study published last year found that an intake above 200mg/day more than doubled the risk. [Am J Obstet Gynecol 2008 Mar;198(3):279.e1-8]
Another recent study found that injecting the caffeine equivalent of two cups of coffee into pregnant mice decreased cardiac function and stunted development of the cardiac ventricles in their offspring. [FASEB J 2008 Dec 16 Epub ahead of print]
The new study, which claims to be the first to give a “true picture” of caffeine intake in pregnancy, found that the association was significant at all levels of consumption and continued throughout pregnancy.
The size of the effect is similar to that seen for alcohol consumption, the UK researchers reported in the British Medical Journal. [2008 337:a2332] They recruited 2,635 low-risk women at 8 to 12 weeks of pregnancy and followed them up until birth.
An intake of more than 200 mg/day of caffeine was linked to an average birth weight reduction of up to 70g (P = 0.004) and increased the odds ratio for having a growth restricted baby to 1.5, as compared to an intake of below 100 mg/day (P = 0.02).
Dr. Shephali Tagore, an associate consultant in the department of maternal fetal medicine at KK Women’s and Children’s Hospital, Singapore, said the study confirms that the advice to reduce caffeine intake before and during pregnancy is appropriate.
“While previous studies have suggested a risk, this study group has objectively quantified caffeine from all known sources. This is a major strength of the study. They have found a dose-response relationship, showing that increasing caffeine intake was associated with increasing risk of fetal growth restriction,” she said.
Tagore added, however, that it is difficult to draw firm conclusions from the paper since there was no control group of women who did not consume any caffeine during pregnancy,
Previous studies have overestimated the impact of tea and coffee and relied too heavily on retrospective recall of caffeine consumption, according to the authors, who took a more thorough approach by using a comprehensive questionnaire which was validated against food diaries and saliva samples.
They found that only 14 percent of the women’s caffeine intake came from coffee. Tea was the major source, comprising 62 percent of intake, with cola drinks and chocolate contributing 12 and 8 percent respectively.
“We believe that, for the first time, this reflects a true picture of total caffeine intake by women during pregnancy,” they wrote. “Our findings emphasize the weakness of studies where caffeine intake was equated to that of coffee alone.”
Caffeine is absorbed rapidly and can cross the placenta freely. The main enzyme for breaking down the compound, however, is not found in the placenta or fetus so exposure depends largely on maternal metabolism.
To investigate whether individual metabolic differences affected fetal growth the researchers also measured the half-life of caffeine in the women’s saliva. The association with fetal growth restriction was strongest in women who had the fastest caffeine clearance but this result did not reach significance (P=0.06).
Caffeine consumption has also been linked to miscarriage. A study published last year found that an intake above 200mg/day more than doubled the risk. [Am J Obstet Gynecol 2008 Mar;198(3):279.e1-8]
Another recent study found that injecting the caffeine equivalent of two cups of coffee into pregnant mice decreased cardiac function and stunted development of the cardiac ventricles in their offspring. [FASEB J 2008 Dec 16 Epub ahead of print]
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