Pregnant woman drinking – Justin Paget/Digital Vision
Pregnant women are often told to avoid coffee, but now evidence suggests they may also need to ditch their daily cup of tea.
An unborn baby’s exposure to caffeine has been linked to shorter childhood height by a new analysis from scientists at the US National Institutes of Health.
Data show that just 50mg a day, the same as half a cup of coffee or one cup of tea, can lead to a child being almost an inch shorter than their peers by age eight.
NHS guidance states a woman should not have more than 200mg of caffeine a day when pregnant, equivalent to two cups of instant coffee. High intake of more than 300 or 350mg a day has been linked to lower birthweight, preterm birth and, in some cases, miscarriage.
The US team looked at two cohorts of children totalling almost 2,500, and assessed how maternal caffeine intake in pregnancy affected their height.
Shorter than their peers
They found that a child whose mother was in the top 25 per cent of caffeine intake, around the same as a cup of coffee, was an average of 2.2cm (0.8in) shorter than their peers.
“Compared to the lowest quartile, children in the highest quartile were approximately 1.5cm to 2.2cm shorter at ages seven to eight,” study author Dr Jessica Gleason told The Telegraph.
“The first quartile is equivalent to almost no caffeine consumption, while the top quartile is estimated to be equivalent to about one cup of coffee per day.”
Melanie McGrice, an advanced accredited practising dietitian and a founding member of the Early Life Nutrition Coalition, said mothers are often confused by recommended caffeine intake guidance.
“This study found that even 50mg a day of caffeine may have a significant impact on children’s height,” she said. “50mg/ a day is equivalent to approximately one cup of tea or half a cup of instant coffee or a family-sized block of chocolate.
“This study adds to the growing body of evidence that caffeine intake during pregnancy has a more significant impact than was once thought, and given there are no advantages for caffeine intake during pregnancy, it seems prudent to advise pregnant women to avoid caffeine if possible.”
Study called ‘questionable’
But some scientists have criticised the study, with Dr Alex Polyakov, of the University of Melbourne, calling the study “controversial” and “questionable” as it cannot prove causation.
“It is possible, perhaps even likely, that those who drink more coffee may have other significant differences in their diet, lifestyle or some other unknown factor that would explain the findings and coffee consumption is not causally linked to the outcomes under study,” he said.
Co-author Dr Katherine Grantz added: “Our findings suggest that even low caffeine intake during pregnancy can have long-term effects on child growth
“Importantly, the height differences we observed are small – less than an inch – and further research is needed to determine if these differences have any effects on child health.”
She advised anyone with concerns to discuss them with their care team.
The findings are published in JAMA Network Open.