Nurture Before Birth
ORIGINS: How the Nine Months Before Birth Shape the Rest of Our Lives. Annie Murphy Paul. xii + 306 pp. Free Press, $26.
When science writer Annie Murphy Paul was pregnant with her second child, she decided to find out what scientists have been able to learn about how the prenatal environment influences later health and development. She found an expanding field that is full of both promise and uncertainty—not unlike the experience of pregnancy itself. Her labors paid off, for she delivered both a healthy baby boy and an entertaining popular science book.
In the book, Origins: How the Nine Months Before Birth Shape the Rest of Our Lives, Paul provides an accessible review of the research on prenatal influences, combining it with the story of her own pregnancy. The reader follows along as Paul tries to make sense of sometimes conflicting findings and to apply their lessons to her own behavior. Trying to provide the best possible environment for one’s child without becoming overprotective or neurotic is a balancing act that many parents will find familiar, and Paul does a good job of describing its tensions.
Paul traces modern scientific interest in this subject back to the 1980s, when British researcher David Barker found a correlation between birth weight (an index, albeit not a great one, of prenatal nutrition) and heart disease later in life: People who weighed less at birth were more likely to develop heart disease in middle age. This and other findings of relationships between environmental conditions during pregnancy and later health outcomes became known as research on “fetal origins of adult disease” and then later as “developmental origins of health and disease” to reflect recognition that conditions both before and shortly after birth are related to both positive and negative outcomes. Paul uses the term “fetal origins” to indicate her focus on the prenatal period.
Although not a scientist herself, Paul is a sophisticated reviewer of research. She understands and explains the limitations of correlational evidence, incorporates other sorts of evidence such as animal studies and natural experiments where available and appropriate, and provides references in endnotes. She also offers an interesting historical perspective, describing how ideas about the effects of a pregnant woman’s behavior, experiences and emotions on her child’s development have evolved over the ages.
Origins is not a how-to guide to pregnancy, but expectant parents will find plenty of food for thought. Paul tries to emphasize that the prenatal period can be the source of positive as well as negative influences on later development; she clearly does not want to add to the pressure and paranoia that many pregnant women feel when well-meaning experts publicize potential dangers to unborn children. Nevertheless, more research exists on prenatal risk factors than on protective factors, so the list of “don’ts” for pregnant women ends up longer than the list of “dos.” In fact, Paul is really able to come up with only two ways of promoting positive outcomes: Pregnant women should eat healthy food (here she recommends following the advice of Michael Pollan) and engage in moderate-intensity exercise (which is associated with better health for both the mother and the fetus, and with higher IQ scores later on).
Paul describes how some myths about pregnancy have misled the public. For example, in the first half of the 20th century many American obstetricians believed that the fetus was a “perfect parasite,” extracting whatever nutrients it needed regardless of maternal diet, and that pregnant women therefore didn’t need to worry about what they ate. More recent research indicates that prenatal nutrition is related to health later on, although recommendations about what pregnant women should eat are often confusing or contradictory. Paul also argues that the modern belief in what she calls the “Pregnant Superwoman,” who needs no special accommodations or support, can exacerbate maternal stress, which is associated with negative outcomes such as premature birth and schizophrenia later in life.
Paul avoids overly simple prescriptions. When she warns of the risks of stress, she also cites Janet DiPietro’s findings that a moderate level of maternal stress may actually be optimal for child development. And with regard to prenatal diet, she argues that eating fish is not simply good or bad—rather, it depends on the particular type of fish. The benefits of omega-3 fatty acids for fetal brain development must be weighed against the risk of mercury contamination, which will be less for fish low on the food chain. Another of the book’s virtues is that Paul does not shy away from the implications of fetal-origins research for controversial topics, such as sexual orientation, abortion, autism and exposure to chemicals such as bisphenol A.
One of the fascinating ideas coming out of the fetal-origins field is that the fetus receives cues about the external environment from the mother and adjusts its development accordingly. In other words, the fetus is already adapting to an environment it hasn’t yet experienced directly. Problems can arise, however, when these cues turn out to have been misleading, as will be the case when the environmental conditions change after birth. For example, David Barker and others have found that famine conditions during gestation predict later obesity, diabetes and heart disease, presumably because children’s metabolisms are prepared for food scarcity that they do not actually encounter. Paul describes epigenetic research that is illuminating the mechanisms that underlie such effects. Prenatal environmental cues can affect gene expression, turning genes “on” and “off” in ways that can even be passed on to subsequent generations.
The book is interesting and well-written. Unfortunately, however, it is not well organized. The nine chapters are labeled with the months of pregnancy (“One Month,” “Two Months” and so on), which leads the reader to believe that each chapter will discuss environmental influences on development during that month. But that’s not the case. Although Paul does recount her own pregnancy chronologically throughout the book, culminating in the birth of her son in the final chapter, the chapter titles are otherwise uninformative as to the content of each chapter. The first chapter is an introduction. The second through sixth chapters focus on different topics (diet, stress, toxins, gender and maternal mood), although you only find out what the topics are as you read each chapter. But then, just as you have come to expect that all of the chapters will be organized topically, the last three chapters have no discernible central topic; rather, each is a grab bag of topics, including some that have already been covered in the previous chapters. Perhaps that’s because each of these later chapters seems to have been written to be a standalone article. So the organization is confusing and a little frustrating. Fortunately, the book does have an index that can help the reader find information on particular topics.
Paul argues that developmental researchers have often emphasized either genetic or postnatal environmental influences and have neglected the importance of the prenatal period. The fetal-origins research summarized in her book clearly demonstrates that the concept of nurture needs to include the prenatal period. Readers will come away convinced that environment—and parenting—begin at conception rather than birth.
Origins is the second popular science book on prenatal environmental influences to be published recently. Researcher and science writer Dan Agin’s More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children was published by Oxford University Press in October of 2009 and covers much of the same ground as Origins. Like Paul, Agin reviews research in an accessible way. However, his book does not include a personal story like hers and is more alarmist in tone, emphasizing prenatal environmental risk factors, especially for disadvantaged populations. I would recommend Origins for readers more interested in the research from a personal and parenting perspective, and More Than Genes for those more interested in policy and public-health implications.
Ethan Remmel is a cognitive developmental psychologist at Western Washington University in Bellingham. His research focus is the relationship between language experience and children’s understanding of the mind.