Cup of coffee
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Coffee shop caffeine levels warning

1 December 2011 Last updated at 07:00 GMT

High Street coffee shops could pose a risk to pregnant women because of big variations in the amount of caffeine in each cup, according to researchers.

Analysis of espresso coffee from 20 shops found that one was six times stronger than others.

The Food Standards Agency says too much caffeine can result in miscarriage or a low birth weight.

Eleanor Bradford reports.