EVEN small amounts of caffeine should be avoided during pregnancy, experts in the US have warned today.

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."