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Monday 24th October 2016

Caffeine linked to miscarriage

21st January 2008

Researchers in the United States have warned that even moderate amounts of coffee in early pregnancy are linked to a greater risk of miscarriage.

The authors of a study in the American Journal of Obstetrics and Gynaecology warned that more than 200mg of caffeine a day; just under three cups of coffee, raised the risk of miscarriage.

Pregnant women should consider avoiding caffeine altogether, they say, although current advice suggests limiting caffeine intake to 300mg a day - or four cups of coffee.

De-Kun Li and colleagues at the Kaiser Permanente Division of Research studied 1,063 women who had become pregnant in the last month or two.

The women kept detailed diaries of their caffeine intake up to the 20th week of their pregnancies.

By 20 weeks' gestation, 172 women had miscarried. Their diaries showed a link between the miscarriages and caffeine consumption.

Compared with non-users, women who consumed up to 200mg of caffeine a day had an increased risk of miscarriage - 15% versus 12%. This increased to 25% among women who drank more than 200mg.

Top obstetricians say they will now be advising women to avoid caffeine entirely during the first trimester of pregnancy.

Pat O'Brien, spokesman for the Royal College of Obstetricians and Gynaecologists, said the first 12 weeks is a very vulnerable time for the baby, when most miscarriages occur.

Many women in early pregnancy dislike the taste of caffeinated drinks, and O'Brien said they should not find total abstention from caffeine too difficult.

But he said more research was needed to clarify whether there was a continued risk from caffeine in later pregnancy.

Other risk factors for miscarriage - which affects one in five pregnancies in the UK - include increased maternal age, a previous history of miscarriage, and infertility.

But previous studies have shown conflicting results regarding the effects of caffeine.

300 mg of caffeine is roughly equivalent to four average cups or three average mugs of instant coffee, three average cups of brewed coffee, or six average cups of tea. Soft drinks are also a risk factor, researchers warn, with 300mg of caffeine contained in eight cans of cola, and just four cans of 'energy' drinks.

Chocolate bars also contain moderate amounts of caffeine, about 300mg in eight 50g bars.

The increased risk appears to be related to the caffeine itself, rather than other coffee ingredients.


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