Body mass index (BMI) is a measurement tool that can assist medical professionals in assessing how much weight a woman should gain during her pregnancy. While body mass index (BMI) is a useful tool in calculating pre- and post-natal health, it should not be used during pregnancy to gauge a woman's fitness level.
The Body Mass Index
Body Mass Index is a number that is determined by looking at the relationship between a person's body weight and height. As a mathematical equation, body mass equals 703 times the quotient of a person's body weight divided by the square of his or her height. For women, a normal BMI range is 18.5 to 24.9. Women who are underweight have a BMI of 18.5 or lower, and overweight women have a BMI of 25 to 29.9. Women with a BMI above 30 are considered medically obese.
Appropriate Weight Gain by BMI
The Institute of Medicine, together with the American College of Obstetrics and Gynecologists and the March of Dimes, recommend that underweight women (with BMIs of 18.5 or lower) gain between 28 and 40 lbs. during their pregnancies. Women with healthy weights (BMIs of 18.5 to 24.9) should gain 25 to 35 lbs., and overweight women (with BMIs of 25 to 29.9) should gain 15 to 25 lbs. Medically obese women should only gain 15 lbs. during pregnancy and closely monitor their blood sugar due to an increased risk of diabetes.
Recommended Weight Gain by Trimester
Appropriately monitoring her weight gain during pregnancy will allow a woman to reduce her chance of having health problems, including gestational diabetes, high blood pressure and varicose veins.
On average, all women gain between 1 and 5 lbs. during the first trimester. The March of Dimes recommends that women with normal BMIs (18.5 to 24.9) gain 1 lb. every week in the second and third trimesters. Underweight women should gain just over 1 lb. per week in the second and third trimesters, and overweight women should gain just over 1/2 lb. each week in the second and third trimesters.
The American College of Obstetrics and Gynecologists does not recommend that a pregnant woman begin a weight-loss plan during pregnancy no matter what her weight is.
Healthy Eating During Pregnancy
The U.S. Department of Agriculture recommends that pregnant women consume 300 additional calories per day. This includes fruits and vegetables of all colors, especially green ones; proteins, which are the building blocks for tissue growth; carbohydrates, which will give the mother energy; vitamins and minerals for the baby's body formation; and folic acid to build the baby's blood cells. Each day, pregnant women need three to four servings of calcium per day, 6 to 8 oz. of water and a daily prenatal vitamin.
Postpartum BMI
After pregnancy, a woman should once again monitor her BMI and work toward keeping it within the healthy weight range of 18.5 to 24.9 through proper diet and exercise. No woman should begin a post-partum exercise program without the permission of a medical professional. Women who have just had a baby are expected to wait, on average, six weeks to exercise to ensure that their organs and abdominal muscles are ready for the additional strain. Women who have had Caesarian sections must wait at least eight weeks to begin an exercise program.
References
- "Your Journey Through Pregnancy;" Inverness Medical; 2009.
- "Aerobics and Fitness Association of America Nutrition Guide;" Nancy Clark, M.S., R.D.; 1994
- March of Dimes: Maternal Obesity and Pregnancy: Weight Matters
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