Most pregnant women should gain between 25 and 35 pounds over the full pregnancy, but your specific target depends on your pre-pregnancy body mass index (BMI). Women who start pregnancy at a higher weight need to gain less, while those who start underweight need to gain more. These ranges come from guidelines developed by the Institute of Medicine and are still the standard used by obstetricians today.
Recommended Weight Gain by BMI
Your pre-pregnancy BMI is the single biggest factor in determining how much weight you should gain. The current guidelines break down like this:
- Underweight (BMI below 18.5): 28 to 40 pounds
- Normal weight (BMI 18.5 to 24.9): 25 to 35 pounds
- Overweight (BMI 25.0 to 29.9): 15 to 25 pounds
- Obese (BMI 30.0 to 39.9): 11 to 20 pounds
These ranges exist because women who start pregnancy with more stored energy simply don’t need as much additional weight to support a healthy baby. If you’re not sure of your BMI, divide your pre-pregnancy weight in pounds by your height in inches squared, then multiply by 703. Or plug the numbers into any online BMI calculator.
Where the Weight Actually Goes
It’s easy to assume pregnancy weight gain is mostly fat, but the majority supports your baby and the physical changes keeping the pregnancy going. Here’s a rough breakdown of where those pounds end up by the end of pregnancy:
- Baby: 6 to 8 pounds
- Placenta: about 1.5 pounds
- Amniotic fluid: about 2 pounds
- Enlarged uterus: about 2 pounds
- Breast tissue: 1 to 3 pounds
- Increased blood volume: 3 to 4 pounds
- Fat stores: 6 to 8 pounds
That fat isn’t wasted. Your body builds those reserves to fuel breastfeeding and recovery after birth. Together, the non-fat components alone account for roughly 15 to 20 pounds, which is why even women with a higher BMI are encouraged to gain at least 11 pounds.
How Weight Gain Should Progress by Trimester
Weight gain isn’t evenly spread across pregnancy. In the first trimester, most women gain only 1 to 4 pounds total. Some women gain nothing or even lose a pound or two due to nausea, and that’s generally fine.
The real gains happen in the second and third trimesters, when you can expect to put on roughly 1 pound per week if you started at a normal weight. Women who were overweight before pregnancy typically aim for closer to half a pound per week during those later months. The pace feels steady rather than dramatic on a week-to-week basis, but it adds up quickly over 25 or so weeks.
Your calorie needs shift along with this pattern. During the first trimester, you don’t need any extra calories beyond your normal intake. In the second trimester, an additional 300 to 400 calories per day supports the faster growth. By the third trimester, the recommendation rises to about 400 to 600 extra daily calories, bringing the total to roughly 2,400 calories per day for most women. That’s the equivalent of an extra sandwich and a piece of fruit, not eating for two in the way most people imagine.
Weight Gain for Twin Pregnancies
Carrying twins changes the picture significantly. The American College of Obstetricians and Gynecologists recommends these ranges for twin pregnancies:
- Normal weight: 37 to 54 pounds
- Overweight: 31 to 50 pounds
- Obese: 25 to 42 pounds
These higher targets reflect the additional demands of growing two babies, two placentas (or a larger shared one), and a greater increase in blood volume. Weight gain also tends to happen faster with twins, particularly in the second trimester, since the growth curve accelerates earlier.
Risks of Gaining Too Much or Too Little
Gaining within your recommended range isn’t just a guideline for its own sake. It directly affects pregnancy outcomes for both you and your baby.
Gaining more than recommended increases the risk of gestational diabetes, high blood pressure, and preeclampsia. It also raises the chances of having a larger-than-average baby, which can complicate delivery and increase the likelihood of a cesarean birth. After delivery, excess weight is harder to lose, and research consistently links excessive gestational gain with long-term weight retention years later.
Gaining too little carries its own risks. Insufficient weight gain is associated with preterm birth and having a baby who is smaller than expected for gestational age. Babies born too small face a higher risk of feeding difficulties, trouble regulating body temperature, and other complications in the newborn period.
How to Track Your Progress
The CDC recommends weighing yourself once a week, at the same time of day, wearing similar clothing, and using the same scale. Write down your pre-pregnancy weight first, then track the difference each week. You can plot this on a weight gain tracker chart (the CDC publishes free printable versions) that shows a shaded “on track” zone based on your BMI category.
If your gain falls within that shaded zone, you’re doing well. If you drift above or below, small adjustments to portion sizes and physical activity can usually bring things back in line. The key word is small. Pregnancy is not the time to diet or restrict calories aggressively. You should not try to lose weight during pregnancy, even if you started above a healthy BMI. The goal is to manage the rate of gain going forward rather than reverse what’s already happened.
Week-to-week fluctuations are normal. Water retention, a large meal, or even the time of day can swing the number by a couple of pounds. What matters is the overall trend across weeks and months, not any single weigh-in. If your pattern consistently falls outside the recommended range for several weeks, that’s worth bringing up with your provider so you can adjust your nutrition or activity plan together.