How Obesity Leads to Overweight Babies

Maternal Weight Before and During Pregnancy

Like our own weight is influenced by the calories we consume and the amount of exercise we get (or don't get), an infant's birth weight is determined by a combination of genes and environmental factors. These factors include such things as maternal weight before and during the pregnancy, as well as maternal health and lifestyle choices. How the unborn baby is affected by maternal factors begins even before a woman gets pregnant.

Obese women suffer health concerns that accompany that extra weight, including the following:

  • Insulin sensitivity
  • Type 2 diabetes
  • Inflammation
  • Hypertension
  • Stroke
  • Fatty liver disease
  • Gallbladder disease
  • Some cancers
  • Infertility
  • Birth Defects
  • Premature Birth

Losing weight -- even just 10 percent of what the scale says -- before becoming pregnant can help reduce her baby's risk of developing childhood obesity.

While dieting during pregnancy is a no-no, gaining too much pregnancy weight can be detrimental to both unborn baby and mother. Carrying too much body weight during pregnancy puts women at an increased risk for labor and birth complications, as well as preeclampsia (a form of high blood pressure that occurs during pregnancy) and gestational diabetes (a form of diabetes that occurs only during pregnancy). The Institute of Medicine recommends that obese women gain very little weight during pregnancy -- only about 11 to 20 pounds (5 to 9 kilograms) total. That breaks down to gaining about 1.1 to 4.4 pounds (0.5 to 2 kilograms) during the first trimester, and then just 0.5 pound (227 grams) each week through the remainder of the pregnancy [source: Institute of Medicine].

Additionally, study after study shows that moms who are obese during pregnancy increase the risk of babies growing too large in the womb and being born with a higher-than-average birth weight (above the 90th percentile when compared to other infants of the same gender). One study found women who gain more than 53 pounds (24 kilograms) during pregnancy, compared to those who gain around 20 pounds (9 kilograms), are twice as likely to have babies with birth weights of 8.8 pounds (4 kilograms) or greater [source: Hensley]. Another, conducted by the New York City Department of Health and Mental Hygiene, found that almost 10 percent of obese moms had babies with birth weights of more than 8.8 pounds (4 kilograms) -- that's 1.7 times more than those born to normal-weight moms [source: Sun].

A healthy diet along with pregnancy-safe exercise (which can be developed with the help of a doctor) can help to control weight gain during pregnancy.