All You Need to Know About Pregnancy Weight Gain

Pregnancy Weight Gain

How much weight should you gain during pregnancy? That depends on how much you already weigh and how many babies you are carrying. Gaining weight during pregnancy is good for your baby’s development, but a recent study shows that about half of all pregnant women in the U.S. gain more weight than they should and a quarter gain less. Too much weight gain or too little can result in labor complications and affect your baby’s health later on.

What’s the recommended range?

While the ideal weight gain during pregnancy has fluctuated over time, the currently  recommended weight gain is based on a scale known as the Body Mass Index or BMI.

Here’s how it breaks down:

  • Underweight = BMI less than 18.5
  • Healthy weight = BMI 18.5 to 24.9
  • Overweight = BMI 25 to 29.9
  • Obese = BMI more than 30

For example, a woman who is at a healthy weight before getting pregnant will be advised to gain between 25 and 35 pounds. Underweight women can gain more, anywhere from 28 to 40 pounds, while overweight women may only need to gain 15 to 25 pounds. For women who are obese, the recommended weight gain may only be 11 to 20 pounds.

If you’re carrying twins, the recommended weight gain will be higher. A woman who is  a healthy weight before pregnancy may need to gain between 37 to 54 pounds, while an overweight woman carrying twins may want to gain 31 to 50 pounds. An obese woman may be told to gain about 25 to 42 pounds during a multiple pregnancy.

The rate at which you should gain pregnancy weight is less than four pounds during the entire first trimester and averages out to one pound per week during the second and third trimesters.

How does the baby weight break down?

Babies don’t usually weigh 30 pounds, so what does that recommended 25 to 35 pound weight gain consist of? A third of the weight you gain during pregnancy is accounted for by the baby, the placenta and amniotic fluid. The other two thirds are attributed to changes in your body, such as your uterus and breasts growing, extra blood volume, extra fluid and stored fat.

You’ll lose some of that weight when you give birth and the rest usually comes off slowly in the next month to six weeks. Gaining only  the recommended amount of weight will make it easier to revert to your pre-pregnancy weight.

Weight-related complications

Women who start pregnancy at a weight above or below normal are not only more likely to experience pregnancy complications  but also to have infants with health problems. Being underweight can lead to premature birth and low birth weight. Being overweight or obese not only places women at a higher risk for gestational diabetes and preeclampsia, a high blood pressure disorder, but can lead to preterm birth.  Having a large baby increases the likelihood of delivery by a C-section, which takes longer to heal from than a vaginal birth. Overweight babies may also be prone to a higher risk of diabetes, and hypertension later on.

Gaining weight in a healthy way

Being pregnant does mean you’re eating for two but it doesn’t mean you can eat twice as much. Although you should eat well during the first trimester, you don’t really need many extra calories. To gain a healthy amount of weight most pregnant women only need an extra 350 calories a day during the second trimester and 450 extra calories a day during the last trimester.

An extra three hundred calories a day is not a lot of food. It’s one muffin or a baked potato or a cup of soup. So, it’s more like adding a light mid-afternoon snack to an already healthy meal plan than it is letting yourself eat whatever and whenever you want.

If you are already overweight or obese, pregnancy is not a good time to diet as restricting food intake can deprive your baby of important nutrients. However, there are steps you can take to keep weight gain within a healthy range.

  • Eat plenty of whole grains, vegetables, fruits, low fat dairy, and lean protein.
  • Limit foods with added sugars and solid fats.
  • Try for at least 150 minutes of moderate intensity aerobic activity per week. That can be accomplished by walking for about 20 minutes a day.
  • Get a good night’s sleep.

Discuss any concerns you have about weight with your doctor.

The CDC recommends that all women of reproductive age have a BMI screening during regular visits so that weight issues can be addressed before they become pregnant.

Joan MacDonald
Joan Vos MacDonald has written about health and fitness for newspapers, magazines and websites. She is a member of the National Association of Science Writers and the author of two books on health-related topics, "Tobacco and Nicotine Dangers," for young adults, and "High Fit Home," a design book about fitness and architecture. She lives in upstate New York near her children and grandchildren.

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