Pregnant women are advised to drink no more than two cups of coffee a day to cut the risk of giving birth to underweight babies.

The new guidance from the Food Standards Agency comes after research that links caffeine consumption to small babies. Underweight babies are also more at risk of premature death or suffer other developmental problems later in life.

Caffeine is also found in tea, cola, chocolate, cocoa, energy drinks and some medicines as well as coffee.

Scientific research has already linked caffeine consumption to a higher risk of miscarriage during pregnancy. Lower birth weight can also result in spontaneous miscarriage.

The new advice from the watchdog is for pregnant women — and those wishing to become pregnant — to limit caffeine intake to 200mg a day, the equivalent of two average-sized cups of instant coffee.

The previous recommended caffeine intake was a maximum 300mg a day or three cups of instant coffee.

Freshly brewed coffee, which is commonly served at coffee chain outlets, contains an average 140g of caffeine in an average-sized mug.

A cup of tea contains 70mg of caffeine, a 330ml can of cola 40mg, and a 50g bar of plain chocolate 50mg, according to the agency.

The revised limits of caffeine for pregnant women are being introduced after advice from the FSA’s independent Committee on Toxicity, which has decided that low levels of caffeine can harm the unborn child.

Andrew Wadge, chief scientist at the FSA, said: “This new advice doesn’t mean that pregnant women have to cut out caffeine completely, simply that they should be careful and make sure they don’t have too much. We would emphasise that the risks are likely to be very small and believe our new advice, which is based on new research and has been considered by leading independent scientists, is sensible and proportionate.”

Researchers at Leeds and Leicester universities studied the caffeine consumption patterns of 2,645 low-risk pregnant women with an average age of 30. Women whose intake of caffeine was over 200mg a day were more likely to give birth to smaller babies. The study took place between September 2003 and June 2006.

Most women in pregnancy however already drink less than 200mg a day and most in the study drank tea so the revised advice is unlikely to affect many women.

The British Coffee Association in a statement said that in light of the new research it will be immediately revising its own guidance to healthcare professionals and consumers on coffee consumption.

Dr Euan Paul, spokesman for the association, described the new study as a robust review and analysis of all the current evidence pertaining to the consumption of caffeine during pregnancy.

He reminded pregnant women that they can still enjoy decaffeinated coffee throughout their pregnancy.

Health chiefs are anxious that women do not replace caffeine drinks with alcoholic drinks or very sweet soft drinks.

Last week scientists also found that a weekly glass of wine or two during pregnancy did no harm to infants and could benefit their performance on some tests linked to behaviour and vocabulary.

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