Lessons From the Womb
Ah, yes, the water-filled condoms. Astonishing that just a few decades ago, our only images of the fetus were black-and-white blots, impressionistic as clouds—
and today we have three-dimensional movies so vivid they caused my husband and me to rear back in our seats at the ultrasound clinic, like the audience at a 3-D showing of Jaws.
The recent explosion of research on fetal origins has been almost as dramatic, especially because it arrives after a long period of inactivity on the part of the mainstream medical establishment. Before its current boom, the field was led for years by a few lonely pioneers like the British doctor David Barker, who kept amassing evidence for a fetal origin of heart disease while everyone else obsessed about genes or adult health behaviors. By now we all know that a fatty diet, a sedentary lifestyle, and a family history of cardiovascular disease can increase our odds of a heart attack—but the notion that long-ago prenatal influences can affect our risk of adult disease still startles.
You ask, Amanda, why so much of this research focuses on what can go wrong during pregnancy. It's true that the earliest evidence for fetal origins, and still its best-supported findings, concern the effects of a pregnant woman's diet on the later development of conditions like cardiovascular disease, high blood pressure, diabetes, and obesity in her child. Pathology was the starting point for the science of fetal origins, probably because investigating a disease feels more urgent than accounting for perfect health, and discovering why some babies are malformed or sickly seems more imperative than explaining why most babies are born normal.
The fact is that it's enormously difficult to study the fetal origins of either health or disease: difficult to access the study subject, sealed away as it is in a womb; difficult to separate prenatal from postnatal factors, and genetic influences from environmental ones; and difficult to assign groups of fetuses to different conditions for the purposes of comparison. The massive National Children's Study, just getting under way in 30 locations around the country, will follow its 100,000 subjects from before birth to age 21. But many of its results won't be known for decades. So fetal origins researchers have frequently relied on "experiments of nature": real-world events that create fortuitous circumstances for investigation.
The events that provide the basis for these natural experiments are often awful in the extreme: earthquakes, floods, wars, terrorist attacks. One such catastrophe was the freezing rain that fell on eastern Canada in 1998, spurring a scientific inquiry called Project Ice Storm. As you note, the children of women who experienced the greatest adversity during the storm had lower scores on developmental and cognitive tests than the children of women who encountered fewer hardships, though their scores were still above the average for children in the age group. You ask how meaningful these disparities in ability will be for them. It's hard to know, of course, though the differences were not trivial: 2-year-olds in the moderate/high stress group scored an average of almost 20 points lower than their counterparts in the low stress group. This was the case even though the mothers who participated in the study were generally better educated and more affluent than others living in the area. It's not hard to imagine that prenatal stress would have an even greater negative impact on women and children with fewer material resources on which to rely.
You ask, too, why it was objective stress (number of days without electricity, residency at a shelter) rather than subjective stress (feelings of distress reported by the mothers) that was associated with cognitive and language delays in babies and children. Researchers are still figuring out the mechanisms by which stress and other prenatal influences exert their effects on the fetus, but the authors of the ice storm study suggest that reports of subjective stress may capture information about women's personality styles—how likely they were to describe their experience in vivid or dramatic terms. The measures of objective stress, by contrast, tapped something more concrete about how many threatening experiences the women actually underwent while pregnant, and so provided a better gauge of the stress to which their fetuses were exposed.
Research on the aftermath of the ice storm, as well as disasters like Hurricane Katrina and the World Trade Center attack, have led some experts to call for better planning and provisioning for pregnant women in emergencies—such as evacuating pregnant women early when a hurricane or other natural disaster looms, providing information specifically for pregnant women in emergency briefings and public service announcements, and training emergency professionals to be aware of pregnant women's particular needs. These steps seem wise if, as fetal origins research indicates, the fetus is vulnerable to traumatic stress experienced by the pregnant woman.
But it would also be smart to invest resources in addressing more common health issues among pregnant women, since research demonstrates that prenatal conditions matter in everyday circumstances as well as extreme ones. A 2002 study of about 10,000 mother-child pairs, for example, reported that the children of women who while pregnant have elevated blood sugar—but not full-blown diabetes—are more likely to become obese. A 2009 study, the largest of its kind in the United States, found that women who are overweight during pregnancy, even if they're not obese, have a 15 percent increased risk of delivering a baby with certain heart defects. During pregnancy, we're learning, ordinary health problems can cast a long shadow.
I know that such assertions are themselves enough to raise the blood pressure of some pregnant women. I was pregnant while researching and reporting my book, and I was actively looking for an alternative to the stream of ominous messages issuing from newspapers, magazines, and guidebooks. Confronted with this barrage, many pregnant women become guilt-ridden and anxious, doubting their every decision; others dismiss it all as bunk, as cynical scare tactics or paranoid hysteria that should be tuned out. But fetal origins research is for real, and it's not going away. We need to find a way to live with it without making ourselves crazy.
One approach is to search the literature for evidence of positive, proactive steps pregnant women can take—evidence that is at last beginning to become available. You mention fish and folic acid; there are also data to support physical exercise, psychotherapy, weight maintenance, depression screening, and—my favorite—chocolate consumption during pregnancy. (Several studies have now reported that eating chocolate reduces a pregnant woman's risk of preeclampsia, a dangerous high blood pressure condition.)
But more important is reconsidering our attitudes toward the very idea that we shape our children before they're born. We have placed a set of frames on the findings of fetal origins research that are not useful or productive, or even especially accurate or realistic. For example: We see the pregnant woman largely as a source of potential danger to her fetus—ignoring the nourishment and protection her body provides every day and night for nine months. We view pregnancy as a perfectible ideal, a generic goal to be achieved—instead of an early introduction to the world the fetus will soon enter, one as idiosyncratic and particular as the environment we offer our children after birth. And we regard fetal well-being as the concern and responsibility of the pregnant woman alone—neglecting that she can hardly make the air cleaner or the food chain safer all by herself. Ultimately, society as a whole pays the bill.
Perhaps an analogy to (postnatal) parenting would be useful here. We know there are many, many ways to screw up our kids (see Larkin, Philip). We could spend all our time worrying about what we're doing wrong (and some of us do). Or we could learn what research has to say, accept that our influence as parents is crucial but not total, and do what we can to make things go well, knowing that the full results won't be in for another half-century or so.
I practiced, and sometimes succeeded, at taking this perspective during my pregnancy. By and large I came to see the notion of fetal origins not as scary or guilt-inducing, but as beautiful, even wondrous. The idea that we are shaped before birth is an ancient one, found in many cultures, and it's now been given new life by modern science.
But what about you? Like me, you're a science writer who recently had a baby. How did you handle the onslaught of messages that what you do during pregnancy can affect your fetus?
Annie Murphy Paul is the author of Origins: How the Nine Months Before Birth Shape the Rest of Our Lives and the forthcoming Brilliant: The Science of How We Get Smarter.