Even small amounts of caffeine should be avoided during pregnancy, experts in the US have warned.
A study published in the American Journal of Obstetrics and Gynaecology found 200mg of caffeine a day doubled the risk of miscarriage.
Current Food Standards Agency guidelines recommend no more than four cups of coffee a day during pregnancy.
The study – conducted by Dr De-Kun Li – involved 1,063 women who had become pregnant in the last month or two.
The women were asked to provide a diary about their caffeine intake up to their 20th week of pregnancy.
These details were then compared finding 172 women had miscarried by 20 weeks.
Compared with those who did not drink caffeine, women who consumed up to 200mg a day had an increased risk of miscarriage.
For women who drank more than 200mg the risk increased from 15% to 25%.
Dr Li said: ‘This strengthens the association between caffeine and miscarriage risk because it removes speculation that the association was due to reduced caffeine intake by healthy pregnant women.
‘The main message for pregnant women from these findings is that they probably should consider stopping caffeine consumption during pregnancy.’
Pat O’Brien, a consultant obstetrician at University College Hospital, London, and spokesman for the Royal College of Obstetricians and Gynaecologists, told the Times: ‘This is the best evidence we now have on the subject and I will advise patients to avoid caffeine completely, at least for the first 12 weeks of pregnancy.
‘Good studies have shown it may be safer to drink caffeine after that, but no more than 200mg a day is still to be recommended.’
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