Drinking caffeine during pregnancy has been linked to a heightened risk of stillbirth in a new study.

Researchers have said that women should be informed of the risk – particularly if they drink above 300 milligrams a day, or the equivalent of three mugs of instant coffee.

Guidance on the NHS website suggests pregnant women should limit the amount of caffeine they consume to 200 milligrams a day.

Researchers said that limits were “not goals” and the more women can “cut down beyond that the better.

Caffeine is found naturally in some foods and drinks, such as tea, coffee and chocolate. It is also added to some energy drinks, cold and flu remedies and some soft drinks.

A new study, which is due to be published in the European Journal of Obstetrics, Gynaecology and Reproductive Biology next month, examined data from 290 women who lost their babies after 28 weeks gestation across 41 maternity units across the UK between 2014 and 2016.

This was compared to 729 women with an ongoing pregnancy.

Overall, more than half of the women surveyed reduced caffeine consumption during pregnancy, researchers from Tommy’s Maternal and Fetal Health Research Centre at the University of Manchester.

Researchers found that 15% of women who had a stillbirth consumed more caffeine than the World Health Organisation’s recommended upper limit of 300mg a day – compared to 8% of women who did not have a stillbirth.

They concluded that each increment of 100mg per day of caffeine was associated with a 27% increase in the risk of stillbirth.

The authors said that women should be advised to reduce caffeine intake in pregnancy.

Intake of energy drinks appeared to carry a higher risk than coffee and cola.

Study author Prof Alexander Heazell, Tommy’s research centre director and professor of obstetrics at the University of Manchester, said: “Caffeine has been in our diets for a long time, and, as with many things we like to eat and drink, large amounts can be harmful – especially during pregnancy.

“It’s a relatively small risk, so people shouldn’t be worried about the occasional cup of coffee, but it’s a risk this research suggests many aren’t aware of.

“Anyone planning to have a baby needs to know that consuming caffeine during pregnancy can raise the risk of stillbirth and other pregnancy complications, so it’s important to cut down as much as you can; the national guidelines should be the limit, not the goal, and the more you can cut down beyond that the better.

“Breaking habits can be hard, but little things like switching to decaf and swapping fizzy drinks for fruit juice or squash can really help reduce the risk.

“If you’re worried or confused, talk to your doctor or midwife, or use tools like Tommy’s caffeine calculator.”

Tommy’s chief executive Jane Brewin added: “Eight babies are stillborn every day in the UK, and the reasons often have nothing to do with diet and lifestyle – but we know there are some things we can do to reduce the risk of this tragedy, so communicating these latest research findings as widely as possible is a vital part of our mission to save babies’ lives.

“This study found that midwives and internet resources had the most impact on pregnant women’s caffeine consumption, so we need to make better use of their influence to support mothers throughout their pregnancy journey.

“Risk is a complex concept to communicate, so healthcare professionals may need training to help them get these messages across.”

In August another research paper concluded that women who are pregnant or trying for a baby should consider avoiding caffeine altogether

The study, published in the journal BMJ Evidence Based Medicine, examined data from 37 observational studies.

The research, by Professor Jack James, of Reykjavik University in Iceland, found that 32 of these studies reported that caffeine significantly increased risk of adverse pregnancy outcomes including stillbirth, miscarriage and low birth weight.

Leading obstetricians said they would support a review of the current guidance on caffeine.

Commenting on the study, Dr Jo Mountfield, a consultant obstetrician and vice president of the Royal College of Obstetricians and Gynaecologists (RCOG), said: “This study adds to the body of evidence that supports limited caffeine intake during pregnancy.

“The study highlights the importance of women being made aware of the risks linked to consuming high levels of caffeine while pregnant, as well as being provided with clear advice about limiting their intake during pregnancy.

“The study also highlights that woman are not always aware of the caffeine content in the food and drink they consume, in particular high energy drinks, and therefore helping woman to access this information more readily is also important.

“The recommended daily caffeine intake of below 200mg for pregnant women – the equivalent to two cups of instant coffee – is based on extensive evidence in this area, however the RCOG would support a review of these limits in light of this new study.

“Any women who have concerns or worries about their or their baby’s health – including the baby’s movements – should seek medical advice from their midwife or hospital immediately.”

Dr Mary Ross Davie, from the Royal College of Midwives, added: “The clarity this Tommy’s study provides on the need for pregnant women to reduce caffeine from all sources, not just from coffee, is exceptionally helpful, for midwives and pregnant women alike.

“A single energy drink contains half of a pregnant woman’s maximum recommended daily allowance of caffeine – 200mg – yet she may not realise it.

“It is so valuable for midwives, maternity care professionals and women to understand more about this crucial issue so that we can continue to reduce the number of stillbirths each year in the UK.”