Drinking two or more cups of coffee per day while pregnant may damage the baby’s liver, research suggests.
Too much caffeine may slow down the development of the organ and boost a child’s risk of developing fatty liver disease or diabetes in adulthood.
A study on rats found 120mg of caffeine per day was enough to reduce levels of a hormone vital to the liver’s growth.
And the same effect may apply to humans, the scientists suggest, when women have drinks with caffeine in them while they’re pregnant.
This is a ‘common’ habit, the researchers said, with coffee, tea and soft drinks popular among expecting mothers.
One expert, however, said the research was too weak to put women off drinking tea and coffee while pregnant, and there was no guarantee of an effect on humans.
Researchers said drinking caffeine reduced the levels of a vital growth hormone which could cause development delay to the liver, for which the body later overcompensated (stock image)
Researchers from Wuhan University in China tested their theory by feeding caffeine to pregnant rats and testing their babies.
They found the ones they fed caffeine – starting with a dose of 120mg per day (an average cup of coffee contains about 95mg) – had less healthy offspring.
In the study the scientists gave the rats amounts of caffeine up to the equivalent of nine cups of coffee.
The caffeine caused a drop in a hormone called insulin-like growth factor (IGF-1), which promotes growth in the body and can reduce blood sugar levels.
As a result, the babies were found to have a ‘compensatory’ growth spurt in their livers after birth, which could lead to abnormal development, the team said.
NHS guidelines recommend pregnant women don’t drink more than 200mg of caffeine per day – about two cups of instant coffee.
It says too much caffeine can cause a low birth weight for a baby and may also increase the risk of the mother having a miscarriage.
‘Our results indicate that prenatal caffeine causes an excess of stress hormone activity in the mother,’ said Dr Yinxian Wen, an author of the study.
‘[This could] inhibit IGF-1 activity for liver development before birth.
WHAT IS FATTY LIVER DISEASE?
Non-alcoholic fatty liver disease is caused by too much fat being stored in the organ’s cells.
The disease can cause scarring and irreversible damage to the liver, and can progress to cirrhosis (scarring) and organ failure.
Fatty liver disease usually causes no signs and symptoms, but they can include an enlarged liver, fatigue and abdomen pain.
The illness is caused by obesity, insulin resistance, high blood sugar and high levels of fat in the blood.
Risk of contracting the disease is increased in people with high cholesterol, fat concentrated in the abdomen, sleep apnoea and Type 2 diabetes.
The disease develops in stages, the most mild of which is likely to be undiagnosed unless it’s picked up by chance in other tests.
This makes it difficult to estimate how many people have the disease but as many as one in five people in the UK are thought to have it to some degree, alongside up to 100million people.
A nutritious diet, maintaining a healthy weight and exercising regularly can reduce the risk of fatty liver disease.
Source: Mayo Clinic
‘However, compensatory mechanisms do occur after birth to accelerate growth and restore normal liver function, as IGF-1 activity increases and stress hormone signalling decreases.
‘The increased risk of fatty liver disease caused by prenatal caffeine exposure is most likely a consequence of this enhanced, compensatory postnatal IGF-1 activity.’
Non-alcoholic fatty liver disease is a condition caused by a build-up of fat in the liver – a healthy liver should contain next to no fat or none at all.
The condition is most common among people who are overweight.
It may reduce liver function and increase the risk of type 2 diabetes, high blood pressure and kidney disease in adulthood.
Dr Wen said: ‘Our work suggests that prenatal caffeine is not good for babies and although these findings still need to be confirmed in people, I would recommend that women avoid caffeine during pregnancy.’
However, one expert not involved with the research said Dr Wen’s conclusion was a step too far.
Dr Michelle Bellingham, a science lecturer at the University of Glasgow said: ‘While this is an interesting and extensive study… and builds on previous knowledge that high maternal caffeine consumption may cause detrimental effects to the fetus, we must bear in mind that these results are in rats.
‘Caffeine may not have exactly the same effects as in humans due to inherent species differences (e.g. differences in metabolism, genetic and environmental influences).
‘We need more research done in humans before we know whether these findings translate to people – some pregnant women may choose to avoid caffeine, which would do no harm, but that would be precautionary and isn’t warranted by this study alone.’
Another researcher, Dr Sarah Stock of the University of Edinburgh, said she couldn’t see the relevance.
Dr Stock added: ‘This study shows that rats given large amounts of caffeine in pregnancy have pups that are smaller, and have some changes in liver development.
‘Although this is an interesting study in an animal model, the relevance to human pregnancy is not very clear. The doses of caffeine used in the study were much higher than current pregnancy recommendations.
‘UK guidance is that pregnant women limit caffeine to less than 200mg a day, and most pregnant women in the UK actually consume less than this.’