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Pregnancy Weight Gain Guidelines Explained

WebMD Expert Column

Every woman who is expecting a child ponders pregnancy weight gain. Some take pregnancy as license to eat as much as they want. Others regard pregnancy pounds with disdain and worry that putting on weight during those nine months will forever ruin their figure.

Whatever your opinion about pregnancy weight gain, it pays to know how much is right for you.  Recently released recommendations by an expert panel of the Institute of Medicine (IOM) and the National Research Council -- the first guidelines of their kind in nearly 20 years -- explain how many pounds to put on and how pregnancy weight gain affects your health and your child's health.

But numbers are one thing; putting it into practice is another thing altogether. Here are some common questions women have about their pregnancy weight gain.

How Much Weight Should I Gain During Pregnancy?

The amount of weight you should gain during pregnancy is based on your prepregnancy body mass index (BMI) and how many children you're carrying. BMI estimates body fat based on height and weight. You can calculate your BMI on the WebMD BMI Plus Calculator.

Once you know your BMI, you've got a starting point for pregnancy weight gain. Women with higher BMIs are advised to gain less; those with lower BMIs should put on more pounds with pregnancy.

Here is a summary of weight gain guidelines for a single baby based on your BMI:

  • If your BMI is less than 18.5: Gain 28 to 40 pounds
  • If your BMI is 18.5 to 24.9: Gain 25 to 35 pounds
  • If your BMI is 25 to 29.9: Gain 15 to 25 pounds
  • If your BMI is 30 or greater: Gain 11-20 pounds

Here is a summary of weight gain guidelines for twins:

  • If your BMI is less than 18.5: Ask your doctor
  • If your BMI is 18.5 to 24.9: Gain 37 to 54 pounds
  • If your BMI is 25 to 29.9: Gain 31 to 50 pounds
  • If your BMI is 30 or greater: Gain 25 to 42 pounds

When Should I Start Gaining Weight During Pregnancy?

When it comes to pregnancy pounds, timing matters.

Chances are, weight gain during the first three months will be minimal -- and should be, according to the IOM guidelines. 

You don't need any extra calories during the first trimester; although the baby's growth is rapid, he is so small that his development doesn't warrant additional energy. However, you may add some pounds to your frame during the first three months because you're hungrier or because of fluid retention. Some women even lose weight because they don't feel well enough to eat their usual diet.

Once the second trimester starts, and the baby's growth begins in earnest, gaining weight on a steady basis is a must. Plan on putting on about a pound each week with a prepregnancy BMI of 24.9 and below, and about a half pound a week if you had a prepregnancy BMI of 24.9 and above. 

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