There is probably no more important time to watch what you eat than during pregnancy. When a pregnant woman eats, she is feeding the developing fetus. It needs the right amount of fuel, or calories and the proper nutrients to make the miraculous 36-week journey from a few cells to a fully formed infant. Scientists have long known what can happen if an expectant mother doesn't eat enough calories. She risks giving birth to a baby that is physically stunted, has poor cognitive development and is vulnerable to disease. But recently, a new problem has come to light: the risks of consuming too many calories during pregnancy.
Risks of Excess Pregnancy Weight
Recent research shows that women who gain too much weight during pregnancy -- especially early in the pregnancy -- may expose their infants to a whole different set of health risks, including obesity, diabetes and future cardiovascular disease. The findings apply not only to women who gain weight during pregnancy, but also to women who are overweight or obese before they become pregnant.
Babies born to mothers with excessive pregnancy weight gain are heavier at birth, have a higher proportion of total body fat and are more likely to be overweight or obese as children, adolescents and adults. They are more likely to develop type 2 diabetes, asthma and high blood pressure in childhood. And they may have an increased risk for cardiovascular disease later in life.
Research shows that the number of fat cells a person has seems to be set by late childhood and adolescence. Once the cells are there, you can't get rid of them, which is one reason why obesity is so hard to reverse. A recent study found that preschool children who were obese had double the risk of remaining obese as adults. For teenagers, the rate is 85 percent. Babies who begin life overweight have greater odds of becoming overweight adults -- and overweight adults have greater odds of developing cardiovascular disease. In addition, some research shows that children born to overweight mothers have lower levels of "good" cholesterol -- and that may also put them at risk for heart disease.
Too Much of a Good Thing
Scientists are not sure exactly how a mother's extra calorie intake increases the body fat and weight of the fetus. One possibility is that obese women behave like diabetic women in the way they process glucose (sugar) and insulin. That may cause their infants to have extra body fat at birth, just as babies of diabetic mothers do. Another possibility is that excessive nourishment in the womb may affect the hormonal and metabolic environment of the fetus and change parts of the brain that regulate appetite and metabolism. That could have a long-term impact on a person's body weight or insulin metabolism.
More research is needed to understand these mechanisms and what role genetics may play as well. But one thing is clear: Excessive weight gain during pregnancy -- or being overweight before becoming pregnant -- increases the baby's chances of being overweight or obese as a child. And that can have lifelong health impacts.
How Much to Gain -- And What to Eat
While gaining too much weight during pregnancy is a bad idea, so is gaining too little. The goal should be the "Goldilocks" option -- gaining "just the right amount" of weight. How much is that? In 2009, the Institute of Medicine revised its guidelines on pregnancy weight gain to address the issue of women putting on too much weight. The current guidelines call for total weight gains of 25-35 pounds for normal weight women, 15-25 pounds for overweight women and 11-20 pounds for obese women. All of this weight gain should come during the second and third trimesters.
If you are pregnant, discuss with your doctor how much weight you should gain. Also ask about diet and physical activity before, during and after pregnancy -- especially if you are already overweight. In general, you should follow a healthy diet with plenty of fruits and vegetables, whole grains and lean protein. Cut out junk food and other empty calories and don't overdo the sodium. Make sure you get enough of some key nutrients that are essential to the developing fetus. These include protein which is critical for growth (aim for 71 g/day); folate or folic acid to prevent birth defects (800 micrograms/day); calcium, for strong bones and teeth (1,000 mg/day); Vitamin D, also for bones and teeth (600 IU/day); and iron, to prevent anemia (27 mg/day).
Finally, if you are overweight and planning to become pregnant, try to lose the extra pounds before you conceive. It will get you -- and your baby -- off to a good start.
Learn more about pregnancy and the development of mother-baby bond:
TheVisualMD.com: Mother-Baby Bond -- The Biology of Love