Obesity considered in new gestational weight gain guidelines

June 9, 2009

New guidelines for gestational weight gain lower the amount of weight obese women should gain during pregnancy and use lower cutoff body mass indices (BMI) to define prepregnancy weight as underweight, normal, overweight, and obese.

Newguidelines for gestational weight gain lower the amount of weight obese womenshould gain during pregnancy and use lower cutoff body mass indices (BMI) to defineprepregnancy weight as underweight, normal, overweight, and obese. Otherwise, theguidelines do not significantly differ from when they were last revised in 1990,says Michael C. Lu, MD, associate professor, UCLA Department of Obstetrics andGynecology, Los Angeles, CA (pictured left).

"In 1990, our primary concern was preventing low birth weight. In 2009, we havean obesity epidemic," Dr. Lu says. "Half of women are overweight and a third areobese prepregnancy. The more weight gain during pregnancy, the more weight retainedafter pregnancy. Pregnancy weight gain, therefore, is a driver of the obesityepidemic."

The Institute of Medicine and the National Research Council issued the newguidelines at the end of May 2009 after experts extensively reviewed the literaturefor evidence that excess gestational weight gain was associated with adverse effectsin either the mother or child, according to Dr. Lu.

"We found that there was insufficient evidence to link increased gestationalweight gain to long-term health effects of the mother," he says. The guidelinecommittee members also found that results of studies aiming to determine whethergestational weight gain is associated with gestational diabetes wereinconsistent.

"We were also unable to identify published studies indicating that gestationalweight gain is linked to later development of metabolic disorders in the child butclearly there is some association," Dr. Lu says.

Literature reports of increased gestational weight gain and the development ofhypertension during pregnancy were also inconsistent. "Preeclampsia causes edema,which causes weight gain, so we don’t know if the gestational weight gain was therefirst," says Dr. Lu.

There is a strong association between amount of gestational weight gain and birthweight but a weaker association between gestational weight gain and preterm birth,he adds. As for prenatal programming of childhood obesity, literature reports areagain inconsistent, with some studies showing an association between increasedgestational weight gain and others not.

However, there was a 2007 report that found higher systolic blood pressure inthe 3-year-old children of women who had higher gestational weight gain, Dr. Liusays.

The new guidelines recommend that women enter pregnancy with a normal weight andgain an amount during pregnancy within the recommended range for their prepregnancycategory. The guidelines do not recommend that obese pregnant women lose weightduring pregnancy because of the risk of ketonemia. "Ketonemia is associated withneurologic effects in both mother and child, and there is no evidence that ketonemiawould be well managed in many populations," Dr. Lu says. Furthermore, caloricrestriction by the mother during pregnancy may be related to the development ofmetabolic syndrome in the child, he says.

According to the guidelines, healthy American women at a normal BMI of 18.5 to24.9 kg/m² should gain 25 to 35 pounds during pregnancy. Underweight women (BMI<18.5 kg/m²) should gain 28 to 40 pounds, and overweight women (BMI of 25 to29.9 kg/m²) should gain 15 to 25 pounds. These ranges match the 1990guidelines, but a new range is given for obese women (BMI >30) that limits weightgain to 11 to 20 pounds.