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.