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The Womb. Your Mother. and Yourself
Cancer. Heart disease. Obesity. Depression. Scientists can now trace adult health to the nine months before birth.
What makes us the way we are? Why are some people predisposed to be anxious, overweight or asthmatic? How is it that some of us are prone to heart attacks, diabetes or high blood pressure?
There's a list of conventional answers to these questions. We are the way we are because it's in our genes: the DNA we inherited at conception. We turn out the way we do because of our childhood experiences: how we were treated and what we took in, especially during those crucial first three years. Or our health and well-being stem from the lifestyle choices we make as adults: what kind of diet we consume, how much exercise we get.
But there's another powerful source of influence you may not have considered: your life as a fetus. The kind and quantity of nutrition you received in the womb; the pollutants, drugs and infections you were exposed to during gestation; your mother's health, stress level and state of mind while she was pregnant with you — all these factors shaped you as a baby and a child and continue to affect you to this day.
This is the provocative contention of a field known as fetal origins, whose pioneers assert that the nine months of gestation constitute the most consequential period of our lives, permanently influencing the wiring of the brain and the functioning of organs such as the heart, liver and pancreas. The conditions we encounter in utero, they claim, shape our susceptibility to disease, our appetite and metabolism, our intelligence and temperament. In the literature on the subject, which has exploded over the past 10 years, you can find references to the fetal origins of cancer, cardiovascular disease, allergies, asthma, hypertension, diabetes, obesity, mental illness — even of conditions associated with old age like arthritis, osteoporosis and cognitive decline.
The notion of prenatal influence may conjure up frivolous attempts to enrich the fetus: playing Mozart to a pregnant belly and the like. In reality, the shaping and molding that goes on in utero is far more visceral and consequential than that. Much of what a pregnant woman encounters in her daily life — the air she breathes, the food and drink she consumes, the chemicals she's exposed to, even the emotions she feels — is shared in some fashion with her fetus. The fetus incorporates these offerings into its own body, makes them part of its flesh and blood.
Often it does something more: it treats these maternal contributions as information, biological postcards from the world outside. What a fetus is absorbing in utero is not Mozart's Magic Flute but the answers to questions much more critical to its survival: Will it be born into a world of abundance or scarcity? Will it be safe and protected, or will it face constant dangers and threats? Will it live a long, fruitful life or a short, harried one?
Research on fetal origins — also called the developmental origins of health and disease — is prompting a revolutionary shift in thinking about where human qualities come from and when they begin to develop. It's turning pregnancy into a scientific frontier: the National Institutes of Health embarked last year on a multidecade study that will examine its subjects before they're born. It's also altering the perspective of thinkers outside of biology. The Nobel Prize — winning economist Amartya Sen, for example, co-authored a paper about the importance of fetal origins to a population's health and productivity: poor prenatal experience, he writes, "sows the seeds of ailments that afflict adults." And it makes the womb a promising target for prevention, raising hopes of conquering public-health scourges like obesity and heart disease through interventions before birth.
The Origins of Fetal Origins
Two decades ago, a British physician named David Barker noticed an odd correlation on a map: the poorest regions of England and Wales were the ones with the highest rates of heart disease. Why would this be, he wondered, when heart disease was supposed to be a condition of affluence — of sedentary lifestyles and rich food? He decided to investigate, and after comparing the adult health of some 15,000 individuals with their birth weight, he discovered an unexpected link between small birth size — often an indication of poor prenatal nutrition — and heart disease in middle age. Faced with an inadequate food supply, Barker conjectured, the fetus diverts nutrients to its most important organ, the brain, while skimping on other parts of its body — a debt that comes due decades later in the form of a weakened heart.
When he presented his findings to colleagues, he was greeted with hoots and jeers. "Heart disease was supposed to be all about genetics or adult lifestyle factors," says Barker, now 72 and a professor at the University of Southampton in England and at Oregon Health and Science University. "People scoffed at the idea that it could have anything to do with intrauterine experience." Barker persisted, however, amassing evidence of the connection between birth weight and heart disease in many thousands of individuals. For years the idea was known as the Barker hypothesis.
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In time his idea began to win converts. Janet Rich-Edwards, an epidemiologist at Brigham and Women's Hospital in Boston, deliberately set out to disprove the Barker hypothesis. "I was convinced that your current risk factors determine your odds of developing disease," says Rich-Edwards, "not something that happened when you were a fetus." But, she adds, "there's nothing like your own data to change your mind." Rich-Edwards analyzed findings from the Nurses' Health Study, a long-running investigation of more than 120,000 RNs. Even when she took account of the nurses' adult lifestyles and socioeconomic status, the relationship between low birth weight and cardiovascular-disease risk remained robust. "Similar studies have been conducted at least two dozen times since then," she notes. "It's one of the most solidly replicated findings in the field of public health."
As a journalist who covers science, I was intrigued when I first heard about fetal origins. But two years ago, when I began to delve more deeply into the field, I had a more personal motivation: I was newly pregnant. If it was true that my actions over the next nine months would affect my offspring for the rest of his life, I needed to know more.
Of course, no woman who is pregnant today can escape hearing the message that what she does affects her fetus. She hears it at doctor's appointments, sees it in the morning newspaper and in the pregnancy guidebooks: Do eat this, don't drink that, always be vigilant — but never stressed. Expectant mothers could be forgiven for feeling that pregnancy is nothing but a nine-month slog, full of guilt and devoid of pleasure, and this research threatened to add to the burden.
But as I began applying what I learned to my own pregnancy, I developed a very different perspective on fetal origins. The scientists I met weren't full of dire warnings but of the excitement of discovery — and the hope that their discoveries would make a positive difference. We're used to hearing about all the things that can go wrong during pregnancy, but as these researchers are finding out, it's frequently the intrauterine environment that makes things go right in later life.
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