Healthy pregnancy weight gain depends mostly on your pre-pregnancy BMI. For one baby, the Institute of Medicine (IOM) guidelines used by ACOG recommend about 25–35 lb (11.5–16 kg) if you started at a normal weight, more if you started underweight, and less if you started with overweight or obesity. Use the charts below to find your range, then talk with your clinician, because your own target can differ. Not sure of your starting category? Check it with the pregnancy BMI calculator.
Pregnancy Weight Gain Chart: Recommended Total Gain by BMI (One Baby)
| Pre-pregnancy BMI | Category | Total gain (lb) | Total gain (kg) |
|---|---|---|---|
| Below 18.5 | Underweight | 28–40 lb | 12.5–18 kg |
| 18.5–24.9 | Normal weight | 25–35 lb | 11.5–16 kg |
| 25.0–29.9 | Overweight | 15–25 lb | 7–11.5 kg |
| 30.0 and above | Obesity | 11–20 lb | 5–9 kg |
These ranges apply to the whole pregnancy, measured from your pre-pregnancy weight to your weight just before delivery. They are guidelines for a single baby, not a pass or fail score.
Twin Pregnancy Weight Gain
For twins, the IOM gives provisional ranges. Women carrying twins are usually advised to gain more in total, and to gain earlier, than with one baby.
| Pre-pregnancy BMI category | Total gain (lb) | Total gain (kg) |
|---|---|---|
| Normal weight (18.5–24.9) | 37–54 lb | 17–25 kg |
| Overweight (25.0–29.9) | 31–50 lb | 14–23 kg |
| Obesity (30.0+) | 25–42 lb | 11–19 kg |
There is not enough data to set a range for underweight women expecting twins, so your care team will individualise your target. Some sources publish higher figures for this group, which is why a personal plan matters.
Pregnancy Weight Gain by Trimester
Gain is not even. Most people gain only about 1–4.5 lb (0.5–2 kg) in the first trimester, and some gain nothing or lose a little because of morning sickness. From about week 14 the gain becomes steady, at a rate that depends on your starting BMI.
| Pre-pregnancy BMI category | First trimester (total) | Weekly gain, 2nd and 3rd trimester |
|---|---|---|
| Underweight | about 1–4.5 lb (0.5–2 kg) | about 1–1.3 lb (0.44–0.58 kg) |
| Normal weight | about 1–4.5 lb (0.5–2 kg) | about 0.8–1 lb (0.35–0.5 kg) |
| Overweight | about 1–4.5 lb (0.5–2 kg) | about 0.5–0.7 lb (0.23–0.33 kg) |
| Obesity | about 1–4.5 lb (0.5–2 kg) | about 0.4–0.6 lb (0.17–0.27 kg) |
Example: What Does a Normal Gain Look Like at 28 Weeks?
Take someone who started at a normal weight. About 1–4.5 lb in the first trimester, plus roughly 0.8–1 lb a week for the 14 weeks between week 14 and week 28, puts a typical total at about 12–18 lb by week 28. Your own curve can be a little ahead or behind and still be healthy, so look at the trend over several visits rather than a single weigh-in. Not sure which trimester you are in? Check with the due date calculator.
Where Does the Weight Go?
Only part of pregnancy weight is fat. In a typical 25–35 lb gain, the baby is roughly 7–8 lb, and the rest is split across the body changes that support the pregnancy.
| Source | Approximate weight |
|---|---|
| Baby | 7–8 lb (3.2–3.6 kg) |
| Placenta | about 1.5 lb (0.7 kg) |
| Amniotic fluid | about 2 lb (0.9 kg) |
| Uterus | about 2 lb (0.9 kg) |
| Breasts | 1–3 lb (0.5–1.4 kg) |
| Extra blood volume | 3–4 lb (1.4–1.8 kg) |
| Extra body fluid | 2–3 lb (0.9–1.4 kg) |
| Maternal fat stores | 6–8 lb (2.7–3.6 kg) |
You can compare your baby’s estimated size with growth charts using the fetal weight percentile calculator.
What If You Are Gaining Too Much or Too Little?
Gaining outside your range is common and not always a problem, but it is worth raising with your clinician early, because diet, activity, medical conditions and how far along you are all matter. Do not diet or restrict food on your own to correct a high number.
Research is also testing whether the current ranges are right for everyone. A 2024 Lancet study of 15,760 women with obesity in Stockholm and Gotland found that gaining less than the guideline range was not linked to higher risks in obesity classes 1 and 2, and that class 3 obesity may even benefit from lower gain. The IOM and ACOG ranges above are still the standard, so any plan to gain less should be made with your care team.
Eating and Moving During Pregnancy
- You do not need to “eat for two.” Extra energy needs are modest, often about 300 calories a day, and they mostly begin in the second trimester. Estimate yours with the pregnancy calorie calculator.
- Choose nutrient-dense foods: vegetables, fruit, whole grains, protein, and dairy or fortified alternatives.
- Stay active with walking, swimming or prenatal exercise unless your clinician advises otherwise.
- If nausea limits eating, try small frequent meals and see our morning sickness relief guide.
When to Call Your Clinician
Contact your care team if you are gaining much faster or slower than your range, or if your weight jumps suddenly over a few days. Rapid gain with swelling of the face or hands, a severe headache or vision changes can be signs of preeclampsia and needs prompt assessment. See also our pregnancy swelling guide.
Frequently Asked Questions
How much weight should I gain in the first trimester?
Typically 1–4.5 lb (0.5–2 kg) in total. Some people gain none, or lose a little, with morning sickness.
When do you start gaining weight in pregnancy?
Most gain is slow until about week 13. From week 14, steady weekly gain begins, and it is usually fastest in the third trimester.
Is it normal to lose weight in early pregnancy?
A small loss can happen with nausea and vomiting and is often regained in the second trimester. Tell your clinician if you cannot keep food or fluids down.
How much weight should I gain with twins?
The IOM provisional ranges are 37–54 lb for normal weight, 31–50 lb for overweight and 25–42 lb for obesity. Your care team will individualise your target.
What if I am gaining too much or too little?
Do not diet or restrict on your own. Your clinician can review your diet, activity and health and set a plan.
Do these ranges apply to everyone?
They are guidelines. Your health, medical conditions and number of babies can change your target.
How is pre-pregnancy BMI calculated?
Weight in kilograms divided by height in metres squared, using your weight before pregnancy. Or use our pregnancy BMI calculator.
Skip the Math
Use the pregnancy BMI calculator to find your category and see your recommended range instantly.
Sources
- ACOG: Weight Gain During Pregnancy (Committee Opinion)
- Mayo Clinic: Pregnancy weight gain: What’s healthy?
- The Lancet (2024): Safety of low weight gain or weight loss in pregnancies with class 1, 2 and 3 obesity
- PregCalc medical review process
This page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your OB-GYN or midwife about your own pregnancy.
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