If you enjoy your morning cup of coffee, you’re probably wondering if you can continue with your daily caffeine jolt when trying to get pregnant.  It’s a good question — and one that deserves a scientific answer.

What is caffeine and what does it do in the body?

Caffeine is a chemical found in plants such as Coffea sp. (coffee), Camellia sinensis (tea), and Theobroma cacao (chocolate). Plants produce caffeine as a natural pesticide; it is toxic to many insects and pathogens. (study)

When you drink a cup of coffee or tea, your body absorbs the caffeine in 15 – 45 minutes. It then gets broken down over the next 2.5 – 5 hours by an enzyme known as CYP1A2.  The different genetic variants of CYP1A2 determine how quickly your body breaks down and clears out caffeine. More to come on this in the genetics section! (study)

While in the body, the caffeine molecule binds to the adenosine receptor, blocking the receptor. Adenosine is a molecule that builds up in your body over the course of a day as a normal byproduct of brain activity.

Adenosine is part of the ATP (adenosine triphosphate) molecule, which is what your cells use for energy.

By the end of the day, your body has used a lot of energy, leaving more free adenosine in the brain to bind to adenosine receptors. This binding makes you feel sleepy.  This is a big part of what drives people to need to sleep! While you sleep, ATP levels are restored and the free adenosine levels are reset. (study)

When caffeine binds to the adenosine receptor, it blocks the receptor from getting the signal from adenosine. This causes you to feel more alert and refreshed.  It is also why you may get a rebound effect when the caffeine wears off. Adenosine still builds up in the body while the caffeine molecule is blocking the receptors. Once the caffeine molecules have been broken down and eliminated, the adenosine can once again bind to the receptors and make you feel tired.

How does caffeine impact fertility?

Let’s take a look at what some recent research studies have shown on the topic of caffeine and fertility.

Many studies have looked at caffeine intake before getting pregnant naturally or through fertility treatments.

A meta-analysis that combined research from 28 studies found that caffeine intake doesn’t affect the odds of getting pregnant. The results also showed that caffeine intake doesn’t increase the amount of time that it takes to get pregnant. (study)

Not all the studies agree though. There are a couple of studies, one from the 1990s and one from 2001, that showed caffeine consumption of more than 500 mg/day or more than 6 cups of coffee per day increased the time to conception. (study)(study)

While the majority of studies show little impact from caffeine consumption on fertility, being conservative in your caffeine consumption is a good idea.

For women who are undergoing IVF, optimizing nutrition and lifestyle several months before the eggs are harvested is important. But what about cutting out caffeine? Three good studies recently investigated how caffeine affects assisted reproduction. The researchers found no impact from caffeine intake and IVF outcomes. (study)(study)(study)

Studies on caffeine during pregnancy

Numerous studies done on caffeine consumption during pregnancy have been done. These epidemiological studies usually ask a large number of participants to recall how much caffeine they drank at different points during their pregnancy.

Some of the studies show that the women who drank more caffeine were at a higher risk of miscarriage. (study)(study)

Other studies show that the children of women who drank more caffeine while pregnant were more likely to have a higher BMI at age 2 and age 8. (study)(study)

Something to keep in mind with these studies is that while they show a link between miscarriage risk and caffeine consumption, they don’t tell you if caffeine consumption is the cause. It could be something that goes along with the caffeine that is the problem and not specifically the caffeine. For example, people may have high caffeine consumption due to washing down their fast food dinner with an extra large soda. One study showed that 66% of caffeine consumers were drinking soda and 45% were drinking coffee. (study)

Practitioners recommend limiting caffeine intake during pregnancy. Some recommendations put the limit at 300 mg/day of caffeine, while others caution to reduce caffeine to less than 200mg/day. (study)

My personal recommendation is to eliminate the daily caffeine i.e. coffee completely once you know you’re pregnant.  Caffeine is a stimulant and vasocontrictor (narrows the blood vessels so less blood flows through) – neither of which are helpful to a developing baby.  If you get some caffeine from chocolate, that’s not a problem.  However, you really should avoid soda since that’s all forms of toxic.

Caffeine affects some people differently

Have you noticed how some people can drink caffeine all day and still fall asleep quickly? For others, caffeine in the afternoon still affects them at bedtime!

Your genetic variants affect:

• how quickly you metabolize caffeine
• whether it is likely to make you more anxious

If you have your genetic data from 23andMe, AncestryDNA, or another genetics company, you can check your raw data file to see how your genes are impacting your caffeine metabolism.

The CYP1A2 gene codes for the enzyme that breaks down (metabolizes) caffeine in the body.  If you carry a genetic variant that decreases the function of this enzyme, you are likely to feel the effects of caffeine longer.

Check your genetic data for rs762551:

• C/C: Slow break down of caffeine; you may feel the effects of caffeine longer
• A/C: Intermediate break down of caffeine
• A/A: Faster break down of caffeine (study)

There are also genetic variants for the adenosine receptor (ADORA2A gene) that caffeine binds to.  This can affect whether you feel jittery and anxious after drinking something with caffeine in it.

Check your genetic data for rs5751876:

• C/C: no increase in anxiety for caffeine
• C/T: no increase in anxiety for caffeine
• T/T: high caffeine more likely to make you anxious (study) (study)

Practical recommendations

While there isn’t a lot of evidence to show that caffeine is harmful when trying to conceive, an overall healthy diet is important.

If you choose to consume caffeine, choose higher quality beverages, such as organic green tea or organic coffee, rather than a high fructose corn syrup laden soda. This is not only common sense, but also backed by studies showing that pesticide residue can hurt fertility.

Do not drink more than 1 cup of coffee a day.  Stop coffee when pregnant.

Sleep is important to your overall health, especially when trying to conceive. Read more about that here. Make sure your caffeine intake is early enough in the day to have no effect on your sleep.