The Institute of Medicine has just released updated national recommendations for the number of pounds a woman should gain during pregnancy for optimum health to herself and her baby.  This set of revised recommendations is the first the institute has issued since 1990 and the first ever to address healthy weight gain during pregnancy for medically obese women.

The main focus of the recommendations is to highlight the value of achieving a healthy weight even before conception.  Healthy mothers are less likely to develop high blood pressure and gestational diabetes and are less likely to require a C-section delivery.

Babies benefit, too, from healthier mothers.  They are less likely to be born prematurely or gain excess weight themselves when their mothers maintain optimum weight before and during pregnancy.

The Institute of Medicine bases its weight-gain recommendations on body mass index (BMI), a measure of weight versus height.  The medical community uses BMI to assess the health of every individual.  Anyone with a BMI calculated between 18.5 and 24.9 is of medically normal weight.  Anyone below 18.5 is underweight and above 24.9 is overweight.  For pregnancy purposes, the institute lists these recommendations:

• Women of normal weight (BMI between 18.5 and 24.9) should limit weight gain during pregnancy to 25 to 35 pounds
• Overweight women (BMI between 25 and 29.9) should gain between 15 and 25 pounds
• Obese women (BMI 30 or higher) should gain no more than 11 to 20 pounds
• Underweight women (BMI less than 18.5) should gain between 28 and 40 pounds

These guidelines are quite different from what is actually happening in the American population today but do reflect the recommendations of many of the nation’s obstetricians.  About 55% of all American women of childbearing age are medically overweight and today’s woman rarely seeks preconception medical care.  Furthermore, the average woman diagnosed as overweight or obese is more likely to gain five pounds more than the upper limit of the institute’s recommendations.

With these guidelines in mind, Dr. Anna Maria Siega-Riz, a co-author of the revised recommendations, says pregnancy is no time to lose weight; that’s best done before becoming pregnant.  Instead, Siega-Riz, of the University of North Carolina, Chapel Hill, says it’s better to assess a woman’s weight as early in the pregnancy as possible and monitor weight gain accordingly throughout the remainder of the pregnancy.

Siega-Riz says underweight women and those in the normal-weight range should expect to gain one pound each week during the second and third trimesters to allow for fetal growth to progress in healthy fashion.  Women who are overweight and obese should allow a weight gain of just a half a pound each week during these trimesters.

During the institute’s study of pregnancy and weight gain, Siega-Riz says most overweight women say they’d never been told how much weight gain is healthy and to be expected during pregnancy.  She suggests the new guidelines may influence a cultural change regarding pregnancy and dietary habits.