I can’t remember the last time I wasn’t tired but should I drink that coffee? How bad is caffeine for my baby after all?
I remember when I told my parents I was pregnant, my husband and I were over at their house for lunch. After the initial congratulations my dad got up to make everyone coffee; he pointed around the table “Do you want coffee? How about you?” he asked each of us. When he got to me, of course, I answered yes, but then he replied “Oh wait- you can’t have coffee because you’re pregnant! How about chamomile tea?” It was the first of many times when I would be surprised by what I could and couldn’t consume while pregnant.
Over the following weeks, as the fog of the first trimester set in, I couldn’t tell how much of my grogginess was caused by a sudden absence of caffeine, and how much was surging levels of progesterone and estrogen. In any case, I wondered how safe caffeine really was for my developing baby. At an early prenatal appointment, my doctor assured me that a single cup of coffee a day would be fine, but I was so nauseated by the smell at that point that I continued to avoid coffee for most of the first trimester. Nonetheless, once the morning sickness subsided in the second trimester and I began to enjoy a morning coffee again, something I continued to do throughout the pregnancy.
Little did I realize, I was in for a whole new surprise when my daughter was born and the question of caffeine in breast milk came up. Exhausted by the huge life change and the lack of continuous sleep, in the first few weeks of her life, I started to notice my newborn daughter was particularly impossible to put to sleep after I had treated myself to a cup of coffee or chocolate. There were so many factors at play, so it’s hard to isolate single variables contributing to her wakefulness, but I began to wonder whether the caffeine was passing to her in significant enough doses to interfere with her sleep.
While I can consume pretty much any dose of caffeine and sleep unaffected shortly after, my husband is far more sensitive. Sometimes he even has trouble getting to sleep at night if he has an afternoon decaffeinated coffee. I wondered whether my daughter had gotten some of his caffeine sensitivity. Without a certain answer, I decided to just cut out coffee, caffeinated tea, and chocolate to see if I noticed a difference. Sure enough, no caffeine resulted in far fewer sleepless nights with my baby. It’s not science but it was the best I could do.
So here I am, speculating: Is it possible that a baby can be that sensitive to even a small dose of caffeine through breast milk from some morning coffee or a chocolate snack? I also wonder, in the case that she is this sensitive, whether my daily coffee while pregnant could have caused any issues for her when she was still inside me.
The short answer is: yes, caffeine does have an effect on a developing baby in utero and after-birth through breast milk.
But first things first: my doctor’s recommendation wasn’t wrong – consumption of 200-300 mg of caffeine per day is broadly considered safe in many countries, including by the well-respected American College of Obstetrics and Gynecology. So in that regard, the advice I got about caffeine for my baby wasn’t out of the norm. The complicating factor arises when one considers the genetic variability among people and how that impacts the way their bodies interact with this chemical. Let’s start with a little background on how caffeine acts in the human body:
Caffeine consumed in food and beverages is absorbed through the gastrointestinal tract; usually taking about 45 minutes to absorb most caffeine present. The way caffeine works in the brain is by attaching to and blocking adenosine receptors (specifically adenosine A1 and A2A receptors), leading to a cascade of effects that we experience as wakefulness and alertness. Just like any chemical entity in our bodies, eventually, it is broken down (metabolized) and the effect wears off. Caffeine metabolism takes place in the liver, largely by the action of the cytochrome-450 oxidase (CYP1A2) enzyme system. In a typical adult, half of a given dose of caffeine is metabolized in 2.5-4.5 hours; this is called the caffeine half-life and is a way to measure how quickly the molecule is broken down in the body. During pregnancy this metabolic ability is decreased, leading to a caffeine half-life of around 15 hours. Due to its chemical structure, caffeine is readily able to cross from a mother to her baby through the placenta, meaning caffeine is consumed by the mother, the fetus also is getting the same or similar dose. And for breastfeeding: studies show that caffeine can absorb into breast milk within an hour of consumption by the mother.
But the mother’s ability to breakdown the caffeine isn’t the only factor to consider: the baby’s metabolic capacity should be considered too. Studies have shown that newborn babies have far less cytochrome-450 oxidase activity therefore, the half-life of caffeine in a newborn infant can be as high as 100 hours. All this to say: caffeine sticks around much longer in the fetal and newborn body than in adults and therefore it has a more potent effect. Yikes!
So if caffeine is so hard to get rid of for fetuses and newborn babies, why is it considered safe to be consumed during breastfeeding and pregnancy? The answer to this question is not completely clear, but it’s likely due to genetic variation among groups of people. There are plenty of studies of pregnant women that indicate no adverse effects on newborn babies when the mother consumed caffeine in moderation. Studies in animal models confirm this finding, however, since animal model studies allow for a more controlled investigation, they also reveal greater nuance to this paradigm.
In a paper published in 2020, researchers found that while certain groups of mice had no negative impacts from caffeine, others had significant and lasting effects on the health and wellbeing of newborn mice. The proposed variation among individuals about their cytochrome-450 oxidase activity were likely reasons for this variation. The diagram below offers some visualization of reasons for these variations, including differences among individuals in the caffeine target receptors, as well as the cytochrome-450 oxidase activity. In other words, the efficiency by which caffeine acts in the pregnant mother, developing fetus, or newborn is significantly variable in mice – which also means this could be the case in humans.
The effects of caffeine on a developing fetus are vast and range in seriousness but the one that stuck out to me is that prenatal caffeine exposure can lead to intrauterine restricted growth (IURG). This basically means the environment in the uterus interferes with the normal development of the fetus, resulting in a smaller fetus than under normal conditions. The mechanism for why caffeine consumption is associated with IURG is not clear and it may have more to do with the cytochrome-450 oxidase activity more than the caffeine itself. Nonetheless, there seems to be some important linking factors between gestational growth and exposure to caffeine.
Now, I don’t want to jump to any huge conclusions but doing this research has given me pause. My husband has a really hard time with coffee, but as I mentioned before, I am largely unaffected by it, so when I asked my doctor about whether caffeine was safe for my unborn baby, it crossed my mind that she would take after her father but I didn’t dwell on the thought. And sure, my daughter was born healthy and none of the doctors suggested any adverse outcomes but I remember being stunned at how tiny she was when I first saw her. Born at 6 lbs 13 oz, she was about one pound smaller than either I or my sister were when we were born. Is it possible that my daughter got an uncomfortably high dose of caffeine while she was developing inside me? A doctor would probably tell me not to worry about it, but I certainly think it is possible. Is there anything I can do about it at this point? No- but going forward, I can make some changes. For starters, I will continue to avoid all caffeine for as long as I’m breastfeeding, to prevent additional exposure. As for her own caffeine consumption: I’ll have to play that by ear as she grows up because I know I love(d) chocolate and I wouldn’t want to deprive her of the delicious treat. But If I am blessed with any future children, I will make sure to avoid caffeine for the entirety of my pregnancy.
All in all, this investigation gave me more questions than answers but I’m glad to know more and be able to make more informed decisions about the future. I hope you learned something new and useful too!
Works cited:
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