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.

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. 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)	5 to 7 pounds
Maternal body fluids and blood	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.

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.

Related Links

What's happening to your baby

Pregnancy Condition Center: First trimester

Pregnancy & Parenting eMagazine: Registration

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

Reviewed by: Allina Patient Education experts