Living for two

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The child-talent agent admits her safety measures may seem a bit extreme, but she may actually be a model for all pregnant women.

What women eat, touch and breathe during pregnancy now appears to be more important to their babies' health than anyone ever imagined. Mounting scientific evidence suggests that fetuses are surprisingly susceptible to outside influences, such as food, environmental chemicals and pollutants, infections, even stress. Under this theory -- called fetal programming -- babies are born not just with traits dictated by their parents' genes, such as brown eyes and olive skin. They may be born with a tendency to develop asthma, diabetes or other illnesses based on what their mothers ate and were exposed to during pregnancy.

Already known were the obvious, and serious, risks posed by smoking, drinking and drug use. Now researchers are homing in on subtler changes in the fetal environment that can influence a child's health even into adulthood. In one of the most widely relevant examples, given the nation's growing waist size, research has shown that pregnant women with diets high in fat and sugar give birth to children who are more likely to become obese, perhaps because their fat cells are "programmed" in utero for later obesity.

In short, the daily experiences of a pregnant woman may be far from benign.

"Fetal life and early infancy are now recognized as periods of remarkable susceptibility to environmental hazards," says Dr. David Barker, a British researcher who is widely credited with recognizing the link between low birth weight and later cardiovascular disease. "The diets of mothers have massive long-term effects on their babies."

Once confined to experts in fetal health, fetal programming is now attracting scientists who study adult conditions, such as diabetes, heart disease, cancer, asthma, schizophrenia and infertility. By understanding the origins of susceptibility, they hope to understand how such diseases might be prevented, says Jerry Heindel, a biochemist and scientific program administrator at the National Institute of Environmental Health Sciences.

"People are realizing that maybe they've been looking at the wrong time frame for the role of environment and disease," says Heindel, who developed a program at the institute to study the fetal basis for disease.That's not to say that Heindel and other fetal-programming experts are suggesting pregnant women take every possible precaution for fear of dooming their children. Such research is in its infancy, and many questions and controversies remain, Heindel says. And he adds: Diseases are caused by a combination of genes and environment or by many factors that collude.

Still, many fetal-programming experts say reproductive-age men and women need to know that they probably have more control over their children's future health than they realize.

"You can't help but be a little bit scared of everything that could go wrong," says Hartman. "There are a lot of things outside of your control. But I was surprised to learn how much is in my control."

Evidence of susceptibility

History has delivered several sobering reminders that the human fetus is vulnerable to outside influences. Birth defects caused by medications such as thalidomide in the late 1950s and more recently the acne drug Accutane demonstrate that doses that have little effect on an adult can cause devastating changes in a fetus.

"The early teaching was that the placenta offered incredible protection against the fetus," says Dr. Philip Landrigan, chairman of the department of Community and Preventive Medicine at Mount Sinai School of Medicine in New York City. "Thalidomide was the first episode that made the medical profession and public realize that the placenta is not some sort of impervious barrier."

But the most jarring part of the fetal-programming hypothesis -- and the hardest to prove -- is that even seemingly harmless doses of ubiquitous substances at the wrong stage of development can produce deleterious effects.

"More recently we've recognized that you can still have these effects in the absence of disastrous damage," Landrigan says. "We've come to realize that if a pregnant woman eats a half-a-dozen cans of tuna fish at the wrong time of pregnancy, that might be harmful."

Contamination of fish with very high concentrations of methylmercury from industrial sources has caused clusters of severe birth defects in several places around the world. But more recent research, including three large epidemiological studies, suggests that even methylmercury concentrations commonly found in the United States can cause subtle changes in the fetus, such as lower IQ and decreased cognitive performance in childhood, Landrigan says.

Other studies have linked low levels of the vitamin folate and increased levels of the amino acid homocysteine with an increased risk of schizophrenia. In a study published in January in the Archives of General Psychiatry, researchers found that high homocysteine levels in the third trimester doubled schizophrenia risk in the offspring, perhaps by altering brain structure or function or through subtle damage to the placenta to reduce oxygen delivery to the fetus. And increasingly, scientists fear that fetuses and young children may be harmed by pesticides and pollutants that, at the same level, cause no measurable harm in adults. For example, some common pesticides are thought to be so-called endocrine disrupters, chemicals that change hormone function in utero and can affect reproductive organ development and function later in life. A study in the March issue of Human Reproduction found that women who ate more than seven servings a week of beef during pregnancy had sons who were more likely to have poor sperm quality as adults -- possibly due to the hormones fed to cattle.

Likewise, levels of air pollutants commonly found in many urban areas may cross the placenta of a pregnant woman and affect her fetus. More than a dozen studies worldwide have linked air pollution to low birth weight, stillbirth and intrauterine growth retardation. According to the World Health Organization, air pollution can impair lung function in the womb.

The implications of fetal programming are profound, Heindel says. Some preliminary research suggests that an environmental influence in pregnancy may not only affect the fetus but also future generations as well.