Analysis of espresso coffees from 20 shops showed one selling coffee with caffeine content six-times higher than the lowest.
The research team, from the University of Glasgow, said customers were completely unaware of the level of caffeine level they were consuming.
Current advice from the UK Food Standards Agency is for pregnant women to restrict caffeine to below 200mg a day.
The coffee with the most caffeine was a single espresso containing 322mg, and a further three shops sold coffee containing more than 200mg.
Janet Fyle, RCM professional policy advisor, said: ‘It is difficult to tell women what they can and can’t do, but most pregnant women are sensible.
‘Midwives need to be able to provide women with information on caffeine, or let them know where they can get the information.
‘It’s not about telling people what they can do, it’s about providing the information so they can make their own minds up.’
The coffees that researchers analysed were all bought in Glasgow and their findings are published in the latest edition of the
Royal Society of Chemistry journal
Food and Function.
Alan Crozier, from the research team, said: ‘At the low level, a pregnant woman, and others with a need to restrict caffeine consumption, might safely drink four cups per day without significantly exceeding the recommended caffeine intake.
‘In marked contrast, at the higher end of the scale, drinking even one cup of espresso will be well in excess of the advised limit of 200mg a day.
‘Our data represent only a snap-shot of the caffeine contents of espresso coffees, but the range and scale of the results is sufficient to demonstrate that there is a problem, unlikely to be restricted to Glasgow.’
