Pregnancy advice, on the whole, tends to be a list of what not to do: don’t drink booze, quit smoking, avoid raw meat, ditch hot baths. While most advice is common sense (smoking’s bad for adults, let alone developing foetuses and some soft cheese contains listeria, a bacterium that can cause illnesses), not all are immediately obvious. Take the relatively new advice on caffeine, for example.

Before 2008, expectant mums were left to sup up to three cups of coffee in peace. In fact, you’ll probably find that developing a new aversion to coffee was one of the first signs that your own mum, aunt or grandma had that indicated change was afoot. Today, however, many healthcare professionals advise caution around caffeine consumption and highlight the need to cut down on caffeinated drinks during pregnancy.

So, is it dangerous to carry on drinking coffee when you’re pregnant, how much is safe and what’s the science behind the current NHS guidelines?  

The NHS advises that pregnant women consume no more than 200mg of caffeine a day.

For context:

• A mug of filter coffee contains 140mg caffeine
• A cup of tea has 75mg
• One can of Cola has around 40mg caffeine
• A bar of plain chocolate has 25mg
• Two cups of instant coffee come to 200mg caffeine – bringing you to the daily limit 

“Consuming too much caffeine can increase the risk of complications during pregnancy,” says Rhiannon Lambert, registered nutritionist and founder of Rhitrition. “This includes low birth weight, restricted growth and stillbirth. According to research, caffeine may increase the risk of constricting blood vessels in the uterus and placenta, which can result in reduced blood flow to the foetus and therefore, reduce growth.”

Dr Vikram Myrthy, GP and co-founder of Murthy Health tells Strong Women: “Studies have linked caffeine consumption to an increased likelihood of miscarriage, which is particularly concerning in the early stages of pregnancy.”

A 2020 review analysed 48 observational studies and meta analyses of maternal caffeine consumption published over the past 20 years. Thirty-two indicated “significantly increased caffeine-related risk” while 10 either suggested no or inconclusive associations. Nevertheless, the review concluded that a substantial majority of the evidence “reliably associated [caffeine consumption] with major negative pregnancy outcomes”. It also flagged that current evidence doesn’t support the idea that “moderate” caffeine consumption during pregnancy is safe and evidence increasingly suggests that pregnant women and those who are trying to conceive might be better off avoiding caffeine altogether. 

While we tend to think of the first trimester as being the most dangerous, the risk from higher caffeine consumption increases during pregnancy. “During the first trimester, the half-life (or time in which it takes for the substance to reduce to half) [of caffeine] is similar to that of a non-pregnant woman (roughly five hours),” Lambert explains. “However, this time increases throughout the pregnancy and reaches roughly 18 hours by week 38 of pregnancy. Ultimately, caffeine remains in the body for much longer during pregnancy, increasing the risk of complications.”

And interestingly, the effects might be felt way beyond birth. A 2022 study looking into the impact of maternal caffeine consumption looked at kids aged between four and eight, and found that those whose mums had consumed caffeine during pregnancy tended to be shorter than those who abstained. Those findings followed a piece of research published in JAMA Network Open, which found that pregnant women who consumed as little as half a cup of coffee a day on average had slightly smaller babies than women who didn’t.

Now, all of this might sound quite worrying – especially if you’re newly pregnant and have been drinking tea and coffee at your usual rate. But Lambert is quick to try to soothe any first-trimester worries: “The risk of any complications for the foetus is low. It’s beyond the first trimester that pregnant women really need to be aware of reducing their caffeine consumption to under 200mg a day.”

But if you’re looking for an uncomplicated rule, Dr Murthy has a simple recommendation: “When it comes to caffeine consumption, it’s best to avoid it throughout the entire pregnancy. I’d recommend switching to decaf options as soon as you know you’re pregnant.”

It’s worth noting that most NHS GPs and midwives tell women that it’s fine to have a cup of caffeinated coffee every day, so perhaps the key here is moderation. If you’re feeling knackered (as is often the case in pregnancy), think about taking a nap rather than reaching for the kettle. 

Images: Getty