It may be advisable to avoid caffeine all together when you’re expecting, according to a new study - meaning that even a decaf coffee or bar of chocolate may be off the menu for mums-to-be.

Although resources such as the World Health Organisation, American Pregnancy Association and the UK’s National Health Service (NHS) advise limiting caffeine intake to under 200mg daily during pregnancy (around one to two cups of coffee a day), increasing numbers of scientists believe that there is actually no safe limit of caffeine consumption for pregnant women.

The Norwegian study of more than 50,000 women, published this year in the British Medical Journal,  found that any caffeine consumption during pregnancy – even that within the current recommended guidelines - is associated with a higher risk of childhood obesity.

Caffeine – a central nervous system stimulant - passes rapidly through the body, including the placenta, and takes longer to process during pregnancy. 

The researchers on the Norwegian study believe that caffeine in utero may change ‘fetal programming’ and modify the overall weight growth trajectory of the child.

This study is the latest in a series of papers over the years that have highlighted the negative impact caffeine can have on pregnancy, which at high levels has been linked with an increased risk of miscarriage and restricted fetal growth

However, this is the first study to have also looked at the impact of low, rather than only high, maternal caffeine intake on children, and is significant because of the implications for the current official guidelines. 

 “I would agree with the statement that there is no safe level of caffeine consumption during pregnancy,” says Alexandra Chaston, head nutritionist at UAE-based hotel The Retreat, The Palm Dubai.

“As caffeine is a stimulant it may increase your blood pressure and heart rate, both of which are not ideal whilst pregnant. Caffeine is also a diuretic, which means it can cause a loss in body fluids in frequent urination and result in dehydration.

“I would advise to err on the side of caution and avoid drinking caffeinated drinks all together if struggling to get pregnant and when pregnant.”

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Should you cut out chocolate while pregnant?

Since decaf coffee – often thought of as the safe option for expectant women - still retains some caffeine after the decaffeination process, its safety for pregnant women is now in question, as well as other caffeine-containing food and drinks such as chocolate, black tea, green tea, some soft drinks and some over-the-counter medications.

“Although studies have remained generally inconclusive on decaffeinated coffee and its link to miscarriages, I would still advise avoiding it during pregnancy,” says Chaston. “Partly because some caffeine still remains in the coffee after the decaffeination process, but also because decaffeinated coffee contains two other stimulants; theobromine and theophylline, which are not removed when the coffee is decaffeinated.”

The amount of caffeine left in decaffeinated coffee can also vary drastically depending on the brand, the process used and the type of bean, so it’s not always possible to be sure of exactly how much you’re consuming.

It’s not just women who are affected by caffeine, adds Chaston. Research has also shown caffeine can affect sperm health such as count, motility and abnormalities, meaning it may be advisable for both partners to cut out caffeine when trying to conceive.

But, with so many of us relying on our morning cup of tea or coffee to get going in the morning, Chaston has some advice:

“For those who are heavy coffee drinkers, I wouldn’t recommend stopping it cold turkey as you are likely to get unpleasant withdrawal symptoms. I would recommend weaning yourself off the caffeine slowly, reducing a cup per day, and substitute your coffee with a decaf or herbal tea – to gradually coming off caffeine altogether within approximately weeks.

“Herbal teas such as ginger, dandelion tea, peppermint tea, nettle tea and Rooibos tea are good substitutes to coffee and black tea as they are nourishing and satisfying without the depleting effects of caffeine. I advise you speak to your nutritionist, naturopath or herbalist if you have any concerns on which teas are safe to drink whilst pregnant.”

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In the study, all levels of caffeine intake were associated with an increased risk of obesity in the child, although the risk was greatly increased for pregnant women with a high caffeine intake compared to a low caffeine intake.

Very high caffeine intake was defined as 300mg or more per day

High caffeine intake was defined as 200–299mg per day

Average caffeine intake was defined as 50-199mg per day

Low caffeine intake was defined as less than 50mg per day

Guide to the caffeine content of food and drink

Brewed coffee (235ml): 95-165mg

Instant coffee (235ml): 63mg

Decaf brewed coffee (235ml): 2-5mg

Decaf instant coffee (235ml): 2mg

Latte or mocha (235ml): 63-126mg

Black tea (235ml): 25-48mg

Decaf black tea (235ml): 2-5mg

Green tea (235ml): 25-29mg

Cola (235ml): 24-46mg

Dark chocolate (100g): 43mg

Milk chocolate (100g): 20mg

White chocolate (100g): 0mg

Source:  Mayo Clinic and USDA

Read more:

 ‘What to eat (and NOT eat) when you’re expecting’

‘Can you justify eating for two when you’re pregnant?’

‘Do pregnancy cravings carry a secret meaning?’