Most pregnant women know better than to smoke, drink or take illegal drugs. But many mothers-to-be and their doctors may be unaware that a pregnant woman’s diet may have long-term consequences for her child’s health, possibly playing a role in diseases long after the child has grown up.

Karin Michels, an assistant professor in the Department of Epidemiology, explores the prenatal origins of adult-onset chronic diseases in her book The Gift of Health: The Complete Pregnancy Diet for Your Baby’s Wellness–from Birth through Adulthood, published by Simon and Schuster. Kristine Napier, nutrition and culinary consultant, co-authored the book.

Written for a lay audience, The Gift of Health describes the thinking behind the fetal origins of chronic diseases and the latest research, while offering practical information about nutrients and specific meal plans to follow during each trimester. More than 100 recipes are included.

"There is preliminary evidence that a pregnant woman's diet may have far-reaching effects on a child's health. That's very new," said Michels.

Researchers like Michels who study the fetal origins of chronic disease investigate whether events in utero can help trigger the development of chronic diseases such as heart disease, cancer, diabetes, asthma and schizophrenia in adulthood. The field emerged from two World War II tragedies: the dropping of the atomic bomb and the starvation of thousands of people in the Netherlands. The offspring of the atomic bomb survivors had higher-than-normal cancer rates, offering early evidence that molecular changes could take place even before children were born.

The Dutch famine resulted from a Nazi blockade of supplies and a particularly harsh winter in the Netherlands in 1944. An estimated 20,000 people starved to death. Decades later, researchers studied the survivors and their children, correlating several health effects to the gestation of children in their starving mother’s wombs. These children had twice the risk of developing schizophrenia than the average population and were also more likely to be overweight as adults.

British epidemiologist David Barker furthered the field in the 1980s when he discovered that babies born below normal birth weights in England had almost double the risk of developing coronary heart disease when they became adults.

Michels was a pioneer in linking high birth weight to increased risk of breast cancer later in life. The research was the foundation of her doctoral thesis at HSPH and garnered her a paper in The Lancet in 1996. She is part of a small Harvard community that includes HSPH’s Walter Willett, Dimitrios Trichopoulos, Stephen Buka, and Anders Ekbom who are investigating the prenatal origins of adult-onset chronic diseases. Michels refers to her colleagues’ studies in her book.

Michels described a working hypothesis of why a pregnant woman’s diet may have such long-lasting effects on her children’s health. Researchers have identified birth weight as a potential predictor of later health. Michels breast-cancer work is an example of that idea.

"Birth weight is only a marker, though. What does it mean?" said Michels. "One factor that influences birth weight is maternal diet, but that may mean more than just caloric intake. We have indications from animal studies and some evidence from studies in humans that both the total caloric intake and the composition of the maternal diet during pregnancy may be important for the child’s long-term health."

Michels explained that the kind of food a woman eats affects both the hormone levels and the nutrients available to her baby. These elements shape the environment at each stage of a baby’s growth in the womb and is why she has included specific meal plans that give appropriate micronutrients and macronutrients in her book.

Beyond that, as a baby’s body forms in the womb, it may be "programmed" for later life, an idea called the "Barker hypothesis" named after the British epidemiologist. This "programming" may be specific to each trimester. For example, studies have indicated that a baby who is underfed during the first trimester is more likely to become obese as an adult, as if the body from its earliest formation had been programmed to seek the food that had been denied. Yet a baby who is overfed in the third trimester is also more likely to become obese as an adult. By that time in a child’s gestation, it is theorized, the fat cells have become "programmed" to expect certain levels of energy derived from food.

"One of the implications of the research on the fetal origins of chronic disease is that focusing on late-life factors that may affect health is insufficient," said Michels. "We need to look at the whole lifespan, which includes the time spent in utero."

The Gift of Health is available in bookstores and online.

The Gift of Health: The Complete Pregnancy Diet for Your Baby’s Wellness–from Birth through Adulthood features daily meal plans grouped according to trimesters to help pregnant women receive the correct amounts and kinds of nutrients. The meal plan below is for early in the first trimester. A lighter, drier breakfast helps to quiet nauseous stomachs while a substantial snack at night will keep the stomach full into the morning.