A new study, published in the British Medical Journal, suggests that pregnant women who fail to reduce their caffeine intake are at increased risk of having a baby with a lower birth weight.
UK scientists recruited 2635 low risk women who were 8-12 weeks pregnant. Total daily caffeine intake was estimated from four weeks before conception until the end of the pregnancy using a detailed questionnaire (including all potential dietary sources, over the counter drugs and details of potential confounders such as smoking, alcohol intake and nausea). Saliva tests established how fast the women could break down caffeine after consumption (i.e. caffeine clearance rate) as well as nicotine exposure.
Average daily caffeine intake in the overall group was 159 mg, lower than the 300mg limit recommended by the Food Standards Agency in 2001. The caffeine ingested by the pregnant women in this study came mainly from tea (62%), coffee (14%), cola drinks (12%), and chocolate (8%).
The results showed an association between foetal growth retardation and higher maternal caffeine intake even after adjustment for smoking and alcohol intake. Caffeine consumption of >200 mg/day during pregnancy was associated with a reduction in birth weight of about 60-70 g, with a significant trend for greater reduction in birth weight with higher caffeine intake. The relation was observed throughout pregnancy, with no plateau effect (no point where the estimated risk cease to increase with increasing caffeine intake).
The authors recommended that women wanting to conceive and pregnant women limit their caffeine intake. These findings and the results of other studies were considered by independent experts of the FSA's Committee on Toxicity, who advised a change in the FSA's advice on daily caffeine intake for pregnant women to help reduce this low risk even further. The new daily figure is 200mg, which equates to two mugs of instant coffee or 2.5 mugs of tea.
Pregnant women who have been following the previous advice, and limiting consumption to below 300mg a day, should not be concerned. Not only is the risk likely to be very low, but the research also showed that the average daily caffeine intake during pregnancy was already below 200mg, so many pregnant women will not be affected by this change in advice. Those currently consuming more than 200mg a day are advised to simply reduce their caffeine consumption to less than 200mg a day for the remainder of their pregnancy.
For more information, seeCARE Study Group (2008). Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study. British Medical Journal 337:a2332.
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