LASTING PRENATAL EFFECTS

The theory: A baby’s risk for future obesity can be affected by his or her mother’s health and habits during pregnancy.

The research: If a woman has diabetes or smokes during her pregnancy, or is poorly nourished during the pregnancy’s early stages, the risk that her baby will be obese or overweight as a child or adolescent is 1.4 to 2 times greater than it would be otherwise, according to a 2007 study that reviewed the scientific literature from 1975 through 2005.

The same researchers are now trying to figure out the physiological mechanisms behind these effects. Dr. Michael Lu of UCLA, a study coauthor, suggests the following pattern for a mother with diabetes: Her blood sugar is high, and that sugar crosses into her baby through the placenta. So the baby produces excess insulin, and in response lays down a lot of fat cells. The extra insulin also programs the baby to always need too much insulin and not “listen” when the hormone leptin sends instructions to hold down insulin production. (Leptin, a “stop eating” hormone, also tells the pancreas to stop producing insulin.) Together, these events predispose the baby to a lifetime of being overweight or obese as well as toward developing Type 2 diabetes.

A study published this year in the journal Diabetes Care found that the number of women who had diabetes (Type 1 or Type 2) when they became pregnant doubled from 1999 to 2005. For teenagers, the number grew to five times higher.

Lu’s study also found that malnourishment in the early stages of a mother’s pregnancy increases the risk that her baby will become an overweight or obese child. And the frequency of low birth weight babies, which correlates with malnourished mothers, has been rising since about 1985.

Our experts weigh in: “Babies’ vital organs and systems are being programmed during pregnancy,” Lu says. “The seeds of their future health are being planted in the womb.” Dr. George Bray of Louisiana State University notes that long-term effects of mothers’ health on their children’s have been seen historically. “Whether they contribute in today’s surfeit of food is unclear to me,” he says.