Healthy Pregnancy Weight Gain: How Much Is Normal?
How much weight you should gain in pregnancy isn't one number — it depends on your weight before pregnancy. The widely used guidelines come from the Institute of Medicine (IOM) and are based on your pre-pregnancy body mass index (BMI).
IOM Weight-Gain Ranges (Single Pregnancy)
- Underweight (BMI under 18.5): 28–40 lb (12.5–18 kg)
- Healthy weight (BMI 18.5–24.9): 25–35 lb (11.5–16 kg)
- Overweight (BMI 25–29.9): 15–25 lb (7–11.5 kg)
- Obese (BMI 30+): 11–20 lb (5–9 kg)
These are general guidelines for a single baby; ranges differ for twins, and your provider may recommend something specific to your situation.
Where Does the Weight Go?
Most of the weight isn't fat — it's the baby, placenta, amniotic fluid, extra blood, larger breasts and uterus, and fluid retention. The baby itself is typically 7–8 lb; the rest supports the pregnancy.
Pace Matters More Than the Total
Gain is usually slow in the first trimester (often just 1–5 lb total) and steadier in the second and third. Sudden or very rapid gain can sometimes signal issues like excess fluid retention, so mention it to your provider. The goal is steady, gradual gain — not a strict weekly target.
Find your recommended weight-gain range based on your pre-pregnancy BMI.
Pregnancy Weight Gain Calculator →Frequently Asked Questions
How much weight should I gain in the first trimester?
Often only 1-5 lb total. Most weight gain happens in the second and third trimesters.
Is it safe to not gain much weight?
It depends on your starting weight and your provider's guidance. Those who begin at a higher BMI are generally advised to gain less. Always follow your provider's advice.
Does gaining more mean a bigger, healthier baby?
Not necessarily. Gaining within your recommended range supports a healthy pregnancy; excess gain carries its own risks.