To Drink or Not To Drink: Caffeine and Pregnancy by Claudia Copeland, Ph.D.

When I first laid eyes on my positive pregnancy test, I was (and am still, in spirit) a reprobate caffeine addict. Coffee had played a major role in my life, and I can honestly say that I would be a very different person without it. In spite of a naturally sleepy disposition, my several coffees a day have fueled the accomplishment of a molecular biology Ph.D., a rich side life as a semi-professional musician, and a lively avocation in amateur bellydance.
Long nights of study or dance at late-night events were always possible- just consume more coffee, or yerba mate when that stopped working, or KMX when that stopped working...
Though caffeine is my only addiction, I must also admit to a more general penchant towards chemical pleasures. In my old life, balmy New Orleans weekend nights would often stretch into the daylight of morning with the help of whiskey sours and other less-than-healthy concoctions. On weekday evenings, I would savor the events of the day over a glass of red wine before getting back on the computer, sitting with my cat watching the stars and the St. Charles streetcars as they trundled by, or over gin and tonics in conversation with my Beloved on his Marigny balcony.
That was my old life. Then came pregnancy.
Suddenly, my body was no longer my own to use and abuse as I pleased. Though fully aware of America's puritanical bent on inhibiting all less-than-angelic pleasures through shrill and ridiculous exaggeration, I also knew that the warnings were backed by enough truth that they could not be ignored completely. I could no longer safely enjoy the same lifestyle as during my pre-conception days. With half my family in Europe, I know that complete abstinence is not necessary for having healthy babies; drinking wine and coffee during pregnancy is commonplace and, especially in our predominantly Catholic area, healthy babies abound. Nevertheless, I wanted to provide as healthy an environment as possible for my developing Little One.
In spite of my skepticism of the abstinence-only folks, alcohol is not a necessity, and so I easily gave it up, just to "stay on the safe side". The same could be said for other recreational substances and medicinal herbs and pharmaceuticals, which can generally be eliminated or substituted with safer alternatives. But caffeine? In my fatigue filled first trimester, I found myself having extreme difficulty concentrating (or even staying awake) enough to read the research papers necessary for my work as a biologist, making record numbers of "stupid" mistakes at the lab bench, and even falling asleep while driving. My work, and even my life (in the case of nodding off at the wheel), were in danger, and this went well beyond the "withdrawal" period. I had to find some middle ground to stay afloat and still have a healthy baby. Popular websites ranged from unsupported assurances that moderate caffeine use wasn't harmful, to alarmist warnings of dire harm to coffee drinking moms-to-be. As a scientist, my first instinct was to go to the original research. Here is what I found:
Searching through the biomedical literature, I looked at four major categories of caffeine effects on the developing fetus. The first category, major birth defects, was easy to evaluate. Very high levels of caffeine have been shown to cause birth defects in animals (Nehlig & Debry 1994), but the levels at which these effects are seen are so high that they would not practically apply to even staunchly caffeine-addicted humans. To assess whether caffeine has these kinds of effects in humans, epidemiological studies (studies of populations of humans) must be used. In a systematic review of the epidemiological literature on cardiovascular malformations and oral clefts (Browne 2006), no evidence was found that caffeine alone was teratogenic for humans. [Caffeine has, however, been found to increase the risk of birth defects by other substances, such as tobacco and alcohol (Nehlig & Debry 1994)]. In a review of several animal studies and epidemiological studies exploring birth defects in general, Christian & Brent (2001) concluded that moderate caffeine use alone should not put fetuses at risk for birth defects. The outcome of epidemiological studies and the extremely high levels of caffeine needed to cause birth defects in animals is reassuring- moderate caffeine use should not lead to birth defects in humans.
The second category, risk of fetal death, is more tricky. Several studies indicate that high levels of caffeine intake could increase the chances for fetal death. Though studies on this subject tend to have methodological flaws (Matijasevich et al., 2005), and could also suffer from "publication bias" (the fact that studies warning of chemicals that cause harm tend to get published, whereas studies that show that everything is fine and there's no cause for alarm tend not to get published), there is nevertheless enough evidence for a fetal death connection to cause concern. To try to resolve this, a very large epidemiological study was conducted in Denmark. The study (Bech et al., 2005) looked at 88,482 pregnant women and examined both their caffeine intake (measured by the amount of coffee they consumed, since this is the main source of caffeine among Danish women), and confounding factors such as smoking and prepregnancy weight. (Confounding factors can have a large effect; women who are heavy coffee drinkers, for example, also tend to be smokers.) After adjustment for confounding factors, it was found that drinking 8 or more cups of coffee per day had 1.59 times (between1.19 and 2.13) the risk of fetal death as women who did not drink coffee, an increased risk that was statistically significant. Women who drank 4-7 cups of coffee also had an elevated (between 1.19 and 1.63) risk of fetal death, but the difference was small enough that it was not statistically significant. These effects applied especially to coffee drinking later in pregnancy (after 20 weeks). Women who drank between ½ and 3 cups of coffee had either slightly fewer fetal deaths or slightly more fetal deaths than women who did not drink coffee, with no statistical difference. Considering the power of this study (the large number of women), it can be considered legitimately dangerous to drink eight or more cups of coffee per day while pregnant, and even 4 to 7 cups of coffee every day may be cause for concern. It must be kept in mind, also, that the amount of caffeine in different cups of coffee varies greatly, depending on factors such as brewing strength and roasting level. (Dark roasted coffee contains less caffeine than light roasted coffee.) The size of "a cup of coffee" is also not uniform, though this study tried to control somewhat for size, counting a large cup of coffee (a "mug") as two cups.
A recent study of a different type of caffeinated drink was a study in Uruguay looking at pregnant women's consumption of Yerba Mate (Matijasevich et al., 2006). Yerba Mate, or simply "mate" as it is commonly known, is a traditional and commonly consumed beverage in Uruguay. The study found an elevated risk related to 300mg or more of caffeine- about 3 cups of mate per day. This study was not as powerful as the Danish study, with only 1,146 women studied, vs. over 88,000 in the Danish study, but the results are nevertheless cause for concern. Yerba Mate could very well contain other substances besides caffeine, and indeed I have found that (in prepregnancy days) it is a drink that "works" for me when no amount of coffee can keep me awake anymore. This highlights the fact that caffeine-containing drinks other than coffee may give rise to different levels of risk than coffee.
In the third category, low birth weight, studies with contradictory results make it more difficult to assess the affects of caffeine. In one study of Italian mothers (Chiaffarino, et al, 2006), low birth weight was actually inversely associated with caffeine- that is, mothers who drank coffee had a lower risk of low birth weight than those who did not. Other studies, however (i.e. Vic et al., 2003), found an increased risk of low birth weight among caffeine consumers. One large epidemiological study of 2,291 mothers not only recorded the coffee, tea, and soda the women reported drinking, but also measured caffeine metabolites in urine samples from these women. The researchers found that, though low birth weight and preterm birth did not increase with caffeine intake, the amount of caffeine consumption was correlated with lower (albeit normal) birth weight. This effect was small enough, however, that it would only be expected to be of concern with consumption of about six cups of coffee or more per day (Bracken et al., 2003). Interestingly, as with the Italian study, the risk of clinically low birth weight was actually reduced with high levels of urinary caffeine metabolites. It should be noted that caffeine consumption was associated with high levels of cigarette smoking and alcohol drinking, and if these factors weren't taken into account, it would look as if caffeine was associated with low birth weight. In fact, it was high levels of tobacco and alcohol use that were associated with low birth weight. Another large study (Klebanoff, et al., 2002) looked at caffeine metabolites in serum, and found an association between caffeine and low birth weight, but only in women who smoked. Among nonsmokers, there was no increased risk associated with caffeine metabolites, arguably the most reliable method of measuring caffeine exposure to the fetus. Overall, these varied and sometimes contradictory results give some cause for caution towards high caffeine consumption, but do not indicate that moderate caffeine consumption (in the absence of smoking) can be expected to cause low birth weight. A number of other studies looking at low birth weight, preterm birth, and intrauterine growth retardation support these findings; high caffeine use combined with smoking and alcohol drinking is risky for low birth weight, but moderate caffeine use by itself is not.
The fourth category I looked at was that of subtle neurological effects, such as lowered IQ or increases in learning disabilities. One study of head circumference, IQ, and attention at 7 years of age found no effects due to prenatal caffeine exposure (Barr and Streissguth 1991). Though studies of extremely high caffeine exposure to pregnant rats resulted in learning disabilities, these levels are far higher than those that humans would be exposed to. I could find no studies indicating neurological/psychological effects associated with caffeine use in humans. Nehlig and Debry (1994), in a review of the literature up until that year, also found no measurable effects of moderate caffeine consumption by pregnant mothers.
So, with this pile of data in mind, what can women conclude about drinking coffee while pregnant? At one end of the spectrum, drinking a cup of coffee a day can be fairly confidently considered safe. At the other end, there's good reason to believe that drinking more than 8 cups of coffee a day may harm your baby. And in between those extremes? Moms will have to make a decision based on a number of factors. If your lifestyle or constitution doesn't dictate a great need for caffeine, you might decide to cut it out entirely. On the other hand, if you require 4 cups of coffee to function, you may choose to drink the coffee you feel you need. What has my decision been? I take a flexible approach to healthy consumption. I know that falling asleep at the wheel poses a much bigger risk than a small cup of coffee or tea in the morning if I can't shake my sleepiness through exercise or willpower. I also know the reality of needing to be productive at my work, and that sometimes requires caffeine as well. In general, I try to stick to one large cup of coffee a day, with an absolute cap at 1 ½ large cups (3 cups of tea or small cups of coffee). My midwife still admonishes me for my "one cup of coffee a day", but I know that my fetus will be better off with a well-functioning mom. (Not to mention that if I lose my job, I'll lose the health insurance that pays for her exceptional care at our health-conscious natural birth center!)
Above all, we pregnant women need to remember that we are the best judges of what choices will be best for ourselves and our babies. Staying informed is crucial to making good judgments, but equally important is listening to our bodies and our own personal knowledge of what is best for us considering all of the factors in our lives. The chorus of negative voices telling us that we need to live in complete deprivation do not possess a fraction of the knowledge, intuition, or "big picture" consciousness that we do about our own bodies and our own lives. Ultimately, with caffeine consumption as with all of the other decisions we face as pregnant women, a combination of knowledge and listening to our own intuition and personal judgment will empower us to make the best decisions for our babies and ourselves.
Claudia Copeland is a biologist (as well as a musician, dancer, and Mama!).