I started drinking coffee far too early. I blame it for my short stature (nothing to do with my 4’11” grandmother).
And more so than alcohol, the one thing I knew I would miss in these months ahead would be that morning (and sometimes afternoon) cup of coffee.
But do I have to ditch my daily dose of caffeine because I am growing a little human?
The general reviews and advice seem mixed – varying widely from “Oh god no!!!!!” to “hmmm… it’s not so bad”. Yeah, kind of a big range.
The websites attempting to answer this question rationally seem to suggest negative consequences but settle on the jury-is-still-out, limit-your-intake-just-in-case approach.
I decided to look a bit closer at some of the science covering the main concerns on those “Oh, god, no!” sites. Since this post is a bit lengthy, I bolded the categories so that you can fast-forward to the bits you are actually interested in.
A lot of the pregnancy websites offer the strongest evidence for and against caffeine based on two opposing scientific papers that specifically address risk of miscarriage.
First, a 2008 paper by Weng and colleagues published in American Journal of Obstetrics and Gynecology found an association between caffeine consumption and rate of miscarriage. But an article published in Epidemiology by Savitz and colleagues, also in 2008, found that caffeine consumption had no effect on increased risk of miscarriage.
So, what gives? Why such drastically different results. Ah, tis the nature of science, I suppose – so many variables can differ! One potential difference stood out to me – the amount of caffeine that is actually in the “high caffeine intake” group.
How to determine caffeine consumption –
Weng and colleagues (caffeine=BAD) asked the women to recall their overall caffeine consumption since becoming pregnant – essentially “how much caffeine have you had since your last menstrual period?”
Savitz and colleagues (caffeine=OK) asked women to recall how much they consumed before getting pregnant, since becoming pregnant, and at that very moment of the interview.
Can you recall every cup of coffee you have had since getting pregnant?
Pregnant lady population-
Weng et al. included women who came into the hospital to confirm a pregnancy and continue on from there.
Savitz et al. study included women who started visiting a clinic for prenatal care and were planning for pregnancy.
Could the women in Savitz’s study already be limiting their caffeine intake in anticipation of becoming pregnant?
Caffeine consumption classification-
Weng et al. blocked the women into 3 groups: no caffeine, low caffeine (<200 mg/day -pretty much a small cup of coffee a day), and high caffeine (>200 mg/day of caffeine – if you order a tall at Starbucks on a daily basis, this includes you!).
Savitz et al. also classified total caffeine consumption but assigned the “groups” according to the median of overall caffeine consumption for each time point. This actually ended up working out to about <200 mg/day and >200 mg/day for the during-pregancy point.
Hmmm… still pretty similar (although there are a dozen + other small differences between the women included in each study)
One thing that Savitz et al. points out about the limitations of their study is that the women included (remember, these are women that have been actively seeking prenatal care) did not show a high range of caffeine intake (>300-400 mg/day). And this high exposure range is the range that has been suggested to increase risk of miscarriage (discussed in a review by Signorello et al. in Epidemiology in 2004).
So, could the difference simply be that the “high caffeine” group in the Weng et al. study included women who were exposed to higher doses of caffeine than their counterparts in the Savitz et al. study?
(Unfortunately, I couldn’t find this sort of data point in the Weng et al. paper).
Ok, so the advice on this one seems to be – caffeine might be ok… in moderation.
What about other aspects? Growth? Development? Behavioral problems? Cancer?
Growth and development
A 2009 paper by Jahanfar and Jaafar, published in Obstetrics and Gynecology, looked at the outcome of decreasing the amount of caffeine pregnant women drank in the 2nd and 3rd trimester. In this paper, the authors describe a study conducted with a cohort of women who drank A LOT of caffeine (3 cups a day!). Half of these women were tricked into decreasing their intake via decaf coffee while letting the other half continue on feeding their caffeine addiction. Comparing the babies at the end? No effect on birth weight, no effect on length of gestation.
This outcome was also suggested by Jarosz and colleagues in a 2012 paper in the European Journal of Obstetrics & Gynecology and Reproductive Biology who found no association between caffeine and birth weight or risk of premature birth. All women considered in this study consumed less than 300 mg/day.
So contrary to some of the warnings about caffeine – at least from these two studies – it appears that caffeine hooked mama’s don’t birth smaller babies earlier.
Behavior problems later
A 2012 study by Loomans et al. published in Pediatrics found absolutely no evidence for increased risk of behavioral problems in children (5-6 years old) born to mothers who hit the coffee pot.
A 2013 in Cancer Causes Control paper by Bonaventure et al. found increasing risk of childhood acute leukemia with the mother’s caffeine consumption. This risk increase was most evident when comparing mother’s who drank two cups of coffee versus none. Uh oh.
But something to consider – there is a 0.04% chance your child will be diagnosed with acute leukemia and two cups of coffee raises this risk to 0.06%.
Ok, ok, my PhD still doesn’t give me any authority to dispense medical advice to myself or to any of you pregnant readers out there.
But, personally, I’m standing by my morning cup of coffee….
but I’ll keep it small… and stick to single shot lattes.
I was a vegetarian for about 12 years. I didn’t expect to keep up that self-imposed dietary constraint when I went off to college. But, alas, I found myself in vegetarian heaven – Ithaca, NY. Lets just say, ever since then, I love my tofu.
So after a healthy dose of soy last night, it occurred to me –
“Oh, crap, soy = phytoestrogens.”
Quick definition: phytoestrogens are plant-based compounds that have a similar structure to the estrogens that our own endocrine system produces. This similarity allows such compounds to go galavanting around, hitting up the estrogen receptors strategically placed throughout our bodies, mimicking estrogen or blocking our own estrogen. This is not actually entirely a bad thing in adults – there is quite of bit of research coming out showing the beneficial properties of phytoestrogens on aging and cancer and alleviating other health problems.
Back to my pregnancy question.
What is the protocol for eating (or not eating) soy during pregnancy? Am I dosing the seahorse (our affectionate nickname for the growing fetal form) with estrogenic compounds and screwing with the development of this little thing’s reproductive system? Its reproductive behavior? All the other developing systems that are primed and ready to respond to an estrogenic signal?
First, to Google where this gem rose to the top:
Ugh, really? If you didn’t click on the link, don’t bother. The post is USELESS. The papers they cite are OLD and have NOTHING to do with eating soy during pregnancy. Just scary points from studies dosing up babies with soy formula. And, no, I didn’t even bother clicking through the “For a thorough discussion of the dangers of soy products…” link.
Ok, onto the scientific literature.
I searched quite a bit and wasn’t completely satisfied with what I found.
In one paper by Yu et al. published in Behavioural Pharmocology in 2010, the researchers found a masculinizing effect on female behavior for those females exposed to phytoestrogens in utero.
Another paper from 2002 by Klein et al. in Molecular Medicine showed increased spleen and thymus weight for male rat pups born from mothers fed super high concentrations of phytoestrogens. They also found lower testosterone in the male pups even if their mother rats were fed low doses.
But, wait, these are rats. Rats fed chow laced with the compounds being studied. They have no other choice than to eat this every day. What about humans? On a normal human diet? Even I don’t eat tofu every day!
I found the most promising data set in a 2012 paper by Jarrell and colleagues published in Obstetrics and Gynecology International. The researchers were mainly interested in the overall presence of phytoestrogenic compounds that could reach baby from mama. They measured phytoestrogen content in the amniotic fluid during pregnancy and in umbilical cord blood and mother’s plasma at birth.
Phytoestrogens were detectable in the cord blood but at concentrations 3x lower than levels in the mom’s plasma.
But this measurement includes all women measured, whether or not they were active soy-eaters.
For those mamas who disclosed their soy intake, only those eating soy on a daily basis showed any difference in the amniotic fluid as compared to the pregnant ladies who claimed to never eat soy (no comparison shown for cord blood). Even those mamas who ate soy on a weekly basis showed absolutely no difference from the I-never-eat-soy group. A 24 hour clearance? A limited ability of the phytoestrogens to build up in the amniotic fluid with reduced intake? For future research to determine….
Also important to note, ALL the pregnant women, even those in the I-never-eat-soy group, had measurable amounts of phytoestrogens in the amniotic fluid. The cord blood data suggests the same since it is impossible to tease out who is who from the data provided.
So, even if you don’t enjoy a good tofu pup every now and again, you are probably still getting some soy sneaking into your diet.
Interestingly, those mamas carrying female nuggets had higher phytoestrogen content in the amniotic fluid than those carrying male nuggets. How that one works out physiologically is still a mystery.
My take home from this – Unless you manage to eat that tofu just at the precise moment when an estrogenic spike would screw up a key estrogen dependent fetal programming step, you are probably in the clear.
On the positive side of soy consumption – A 1998 paper from Fritz et al. in Carcinogenesis found that rat mothers chowing on a “physiological dose” of a phytoestrogenic compound actually conferred benefits to their daughters. Female rat pups dosed in the womb had reduced susceptibility to developing cancer in their mammary tissue. In humans this could translate to decreased risk of breast cancer!
Advice to myself – I will keep eating tofu… in moderation.
Fast approaching the second trimester which means, I am in “the clear”. At least that is the marker by which we decide when to spread the news far and wide.
So, here we are, internet, I am pregnant.
I am a pregnant scientist.
Field of research, generally? – Physiology.
Specifically? Stress and reproduction.
How appropriate, right? The stress of doing research, looking for a new job, moving, buying a house, LIFE, nearly got in the way of my own reproduction (more on this later?). And, unfortunately, I know all too well why. Ok, so I know, potentially why. If I knew why, I wouldn’t have funding to ask the questions I am asking.
As a physiologist, my first instinct whenever I have all those nagging pregnancy questions is to ignore those pregnancy sites that treat you like a human who has no idea how the human body works and dive right into the scientific literature.
Really? I would ask. But what does the actual research show!?
Hopefully I’ll find some answers, clues, interesting factoids. And I plan to share them here. In no way do I intend this site to be a place to look for advice, so take my “findings” with a grain of salt. I am not a medical doctor, just a curious PhD.
And in the end, I will probably realize that there might be a reason we don’t go off exploring on our own.