With all of the conflicting cultural messages, weight gain can be socially fraught no matter how healthy your body is. But who gets a free pass? You do, pregnant person! Weight gain is a natural and healthy part of pregnancy.
It’s easy enough to gain weight to support this beautiful embryo through all of its developmental stages for months until the baby’s birth, right? Sometimes it’s easier said than done.
So, just how much weight are you actually expected to gain over these 40 weeks?
Average weight gain during pregnancy
Gaining either too much or not enough weight isn’t healthy for you or your baby. According to the U.S. Centers for Disease Control, gaining too much weight is associated with gestational diabetes, a large fetus that could require delivery by C-section and greater risk of childhood obesity.
A too-low pregnancy weight isn’t as much cause for concern in the first trimester, as some women’s nausea and/or food aversions can result in unintended weight loss early on. In later weeks, however, the potential consequences of not gaining a sufficient amount include a preterm delivery and a newborn with a low birth weight. Premature babies and those with low birth weights are at an increased risk for illness, developmental delays and difficulty with starting to breastfeed.
If you wonder where in this range you fall, check the CDC’s guidelines in the table below.
Target weight gain in pregnancy
|BMI before pregnancy||Healthy pregnancy weight gain|
|Underweight (18.5 or less)||28 to 40 pounds|
|Normal weight (18.5 to 24.9)||25 to 35 pounds|
|Overweight (25 to 29.9)||15 to 25 pounds|
|Obese (30 or more)||11 to 20 pounds|
If you don’t already know your body mass index (BMI), a figure based on your height and weight, you can find it by using the calculator provided by the National Heart, Lung and Blood Institute.
Pregnancy weight gain by trimester
If your pre-pregnancy BMI was within the normal range, you should expect to gain about 25 to 35 pounds over 40 weeks. Those pounds obviously won’t come on all at once. So, when will you see the number on the scale start to go up?
First trimester weight gain: During the first trimester, it’s unlikely you’ll see much of a change in your weight. If you’re on track to gain between 1 and 4.5 pounds by the end of week 12 of your pregnancy, you’re within the normal range.
Second trimester weight gain: From week 13 to the end of week 26, you’d be in the minority if you didn’t notice a substantial change in your appearance. Through your second trimester, you’re within the normal range if you gradually gain about 14 pounds — around 1 to 2 pounds or so each week, although your weight might plateau one week and rise the next. Most of this weight is due to your increased fluid and blood volume.
Third trimester weight gain: In the third trimester, you can expect to continue gaining weight — about 1 to 2 pounds a week — though you’ll probably add weight less steadily than you did in the second trimester. A lot of the weight added in the final weeks goes straight onto your baby.
What accounts for this weight gain? Here’s how a 30-pound weight gain breaks down, on average, in pregnancy:
- 7.5 pounds for your full-term newborn
- 7 pounds for maternal stores of protein, fat and other nutrients
- 4 pounds for increased fluid volume
- 4 pounds for increased blood volume
- 2 pounds of additional breast tissue
- 2 pounds of additional uterine weight
- 2 pounds of amniotic fluid
- 1.5 pounds of placenta
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