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First trimester: What's happening to you

Your body

During the first 13 weeks of pregnancy, you barely look pregnant on the outside.

On the inside, things are profoundly different. Your body is...

  • growing a placenta

  • adding breast tissue

  • building up stores of energy

  • adding blood and other body fluids

  • making amniotic fluid

  • creating a healthy baby

Your blood volume nearly doubles during your pregnancy to accommodate your growing uterus, placenta and baby.

 

During the first 13 weeks of pregnancy, you barely look pregnant on the outside.  On the inside, things are profoundly different.

Weight gain during pregnancy

It's natural and important to gain weight during pregnancy.

  • On average, a gain of 21 to 35 pounds during pregnancy is recommended.

  • If you are underweight when you get pregnant, or if you're carrying twins, you'll need to gain more.

  • If you are overweight and in good health, you may be able to gain 5 to 10 pounds less. But don't diet or skip meals, especially during late pregnancy. Your baby has a continuous need for calories.

To see how much weight you should gain during pregnancy, take these steps:

  1. Calculator Calculate your pre-pregnant body mass index (BMI).
  2. Find your number on the left column of the chart below.
  3. Look at the pound range to the right of your pre-pregnancy BMI.
Pre-pregnancy BMI Recommended weight gain during pregnancy

less than 19.8

28 to 40 pounds

19.8 to 26

25 to 35 pounds

26 to 29

15 to 25 pounds

29 and more

at least 15 pounds

if carrying twins or more

35 to 45 pounds

 

Where does the weight go?

Baby

7 to 8 pounds

Amniotic fluid

2 to 3 pounds

Placenta

2 to 3 pounds

Uterine muscle

2 to 5 pounds

Breasts

1 to 2 pounds

Maternal energy stores (fat)

2 to 7 pounds

Total 21 to 35 pounds

 

Ask your health care provider what kind of weight gain is best for you. Your weight will be checked each time you visit your health care provider.

  • You may gain about 3 to 4 pounds during your first trimester and about 1 pound a week for the rest of your pregnancy. However, remember this is only an average.

  • Sometimes, you may even lose weight. This can be from the nausea that is common early in pregnancy.

  • Some women do not gain much weight at all. If your diet is good, if your baby is growing, and if your health care provider says things are fine, try not to worry.

Helpful tip: Ask your health care provider for help in monitoring your weight gain if watching the numbers go up on the scale bothers you, or if you have had any type of eating disorder.

If you think you're gaining too much weight, substitute quality for quantity.

  • Choose nutritious foods. (See Your nutrition needs.)

  • Try to avoid foods that are high in sugar and fat, but low in nutrition.

  • Ask your health care provider for specific recommendations.

Birth Story: "I worried about too much weight gain, especially when I had gained 10 pounds in one month! But then, when I looked at my total weight gain, I found I was right on target." - Barbara, mother of Hannah

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Source: Allina Patient Education, Beginnings: Pregnancy, Birth and Beyond, fourth edition, preg-ahc-90026, ISBN 1-931876-14-2

First published: 10/04/2002
Last updated: 06/01/2003

Reviewed by: Allina Patient Education experts

 


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