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Raising public awareness of the risks of caffeine intake during pregnancy

Studies carried out by Professor Janet Cade and colleagues from the Faculty of Medicine and Health showing the effect of caffeine on the developing foetus have resulted in clearer national guidance, helping women make informed decisions to benefit the long-term health and survival of their child.

Most pregnant women consume caffeine from one or more sources. Previously, animal studies had suggested that caffeine could harm the developing foetus but research in humans had been inconclusive and a level at which harm may occur was unclear. This was largely due to difficulties in accurately assessing caffeine intake and the effect of variation in caffeine metabolism.

A Leeds team designed and conducted the robust Caffeine and Reproductive Health (CARE) study of 2,635 pregnant women to determine the safe level of caffeine consumption in pregnancy. Leeds developed a tool to accurately calculate caffeine intake from all potential dietary sources and over-the-counter drugs. The team also looked at the effects of caffeine consumption across all trimesters as well as prior to conception and developed a novel saliva test to take into account individual variations in metabolism.

"Two thirds of infants who die have a low birth weight. Foetal growth restriction is also linked with adverse effects in later life, including increased incidence of obesity and type 2 diabetes."

The study showed that caffeine consumption at levels of 200mg/day (and maybe even lower) is associated with a significantly increased risk of foetal growth restriction, similar to the size of effect seen for alcohol intake in pregnancy. The findings showed that the association continues throughout the whole of pregnancy. Further analysis found a strong link between caffeine intake in the first trimester and subsequent late miscarriage and stillbirth.

Helping health professionals deliver appropriate care

Previous advice had set a maximum daily intake of 300mg. The Food Standards Agency responded to the findings by publishing new guidelines in 2008, advising women to limit their daily caffeine intake to below 200mg/day (around two mugs of instant coffee a day). This advice has featured extensively in national news reports and been adopted by the NHS, featuring on the NHS Choices website and in the Pregnancy Book, a highly trusted source of advice handed out to all pregnant women in England. The Royal College of Obstetricians and Gynaecologists also highlighted the new advice.

Read the NHS advice ›