A new study from Wuhan University in China has cautioned pregnant women over the dangers of consuming too much coffee.
Researchers revealed that drinking over two cups of coffee a day during pregnancy can impair the development of the baby's liver.
Pregnant rats in the study were given caffeine, and their offspring had lower birth weights, altered growth and stress hormone levels and impaired liver development.
The findings were published in the Journal of Endocrinology, and indicate that two to three cups of coffee per day can change stress and growth hormone levels
These altercations can impair growth and development as well as increasing the chances of contracting liver diseases in adulthood.
Previous studies suggested prenatal caffeine intakes of 300mg/day or more in women (approximately two to three cups) can result in lower birth rates.
Animal studies have also pointed to the notion that prenatal consumption of caffeine might have long-term effects on liver development, with a higher susceptibility to non-alcoholic fatty liver disease.
Researchers say that there is a lack of understanding behind the underlying link between impaired liver development and prenatal caffeine exposure.
Professor Hui Wang and colleagues at Wuhan University in China investigated the effects of low doses (two to three cups of coffee) and high doses (six to nine cups of coffee) on pregnant women.
They discovered that the offspring exposed to prenatal caffeine had lower levels of liver hormone, insulin like growth factor (IGF-1), and higher levels of the stress hormone corticosteroid when they were born.
Dr Yinxian Wen, study co-author, said: "Our results indicate that prenatal caffeine causes an excess of stress hormone activity in the mother, which inhibits IGF-1 activity for liver development before birth.
"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."
Dr Wen added ;"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."
Dr Michelle Bellingham, member of the Society for Endocrinology, said:
"Their results suggest that the mechanisms underlying intrauterine growth restriction induced by maternal caffeine consumption, may involve altered development of foetal liver signalling pathways and growth factors.
"While this is an interesting and extensive study which attempts to increase our understanding of how caffeine can affect foetal development, and builds on previous knowledge that high maternal caffeine consumption may cause detrimental effects to the foetus."
Dr Bellingham; "We must bear in mind that these results are in rats, in which caffeine may not have exactly the same effects as in humans due to inherent species differences.
"The authors acknowledge that their findings still need to be confirmed in humans," she added.
Dr Sarah Stock from the University of Edinburgh, said:
"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."
