Weight Gain During Pregnancy: What Is Normal?

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Pregnancy: Healthy weight gain guidelines, recommendations and risks

Some individuals mistakenly believe that the weight gained during pregnancy is basically fat plus the weight of the infant. In reality, that only accounts for about 12 to 15 lbs. The factors that, for the most part, determine how much weight you should gain include your pre-pregnancy weight and whether or not you are having a single birth or multiple births (twins). There are always exceptions to this rule: women that appear to gain little more than the weight of the fetus. Remember, this is the exception and is, for the most part, unusual.

How much weight should I gain during pregnancy? What is the average weight gain during pregnancy?

In general, the weight you gain over the course of your pregnancy is distributed as follows:

Increase in breast size = 2 to 3 lbs.
Increase in mother’s blood volume = 2 to 4 lbs.
Placenta = 1 to 2 lbs.
Increase in blood supply to the placenta = 4 to 4½ lbs.
Amniotic fluid = 2 lbs.
Infant at birth = 7 to 8 lbs.
Increase in size of the uterus = 2 to 2½ lbs.
Mother’s fat stores = 5 to 8 lbs.

Totaling the above adds up to about 25 to 35 lbs. which is considered to be the average/recommended weight gain for most healthy women. This is for a single pregnancy in a woman already within a normal weight range (as determined by Body Mass Index or BMI). A normal BMI is 18.5 to 24.9. Underweight women or those with a BMI of less than 18.5 may need to gain more weight during pregnancy, 28 to 40 lbs. It is recommended that overweight women, on average, with a BMI of 25 to 29.9, gain a total of 15 to 25 lbs. Women that are obese pre-pregnancy, with a BMI greater than 30 should gain approximately 11 to 20 lbs. During the first trimester, total weight gain is only 2 to 4 lbs. After the first trimester, a gain of approximately 1 lb. per week is normal.

What if I am expecting twins?

You will gain more weight for a multiple birth pregnancy. The recommended weight gain range is also determined by pre-pregnancy weight. A woman with a normal BMI pre-pregnancy, expecting twins may gain about 37 to 54 lbs. If you are overweight, total weight gain should be lower overall, 31 to 50 lbs. The recommended total weight gain for obese women, with a BMI of > 30, is about 25 to 42 lbs.

Are there health risks associated with gaining too much weight?

Yes, gaining too much weight during your pregnancy can be harmful to you and your growing infant. Usually, this occurs when a pregnant woman overeats, has poor diet and exercise habits, takes in too many high calorie foods and/or is overweight or obese pre-pregnancy. Gaining a few extra lbs. may not be a concern; however, gaining too much weight (will vary by individual, consult your physician for specific information) may be dangerous. Pregnant women that gain too much weight are more likely to develop diabetes during their pregnancy (known as gestational diabetes) and high blood pressure, especially those with a family history of these conditions.

REFERENCES

Drummond, K.E. & Brefer, L.M.: Nutrition for Foodservice & Culinary Professionals, 7th ed. John Wiley & Sons, Inc., New York, 2010.
Mayo Clinic – Pregnancy Week by Week: Pregnancy Weight Gain: What’s Healthy?
American Pregnancy Association: Eating for two when over/underweight.