How much weight should you gain in pregnancy?
The right amount depends on your body mass index (BMI) before pregnancy. These ranges come from the US Institute of Medicine (IOM, now the National Academy of Medicine) 2009 guidelines, used by ACOG and doctors worldwide. Most women gain only 0.5–2 kg in the first trimester, then gain steadily at the weekly rate below.
| BMI before pregnancy |
Total gain (one baby) |
Per week, 2nd & 3rd trimester |
Total gain (twins) |
| Underweight (below 18.5) |
12.5–18 kg (28–40 lb) |
0.44–0.58 kg (1–1.3 lb) |
No guideline — ask your doctor |
| Healthy (18.5–24.9) |
11.5–16 kg (25–35 lb) |
0.35–0.50 kg (0.8–1 lb) |
17–25 kg (37–54 lb) |
| Overweight (25–29.9) |
7–11.5 kg (15–25 lb) |
0.23–0.33 kg (0.5–0.7 lb) |
14–23 kg (31–50 lb) |
| Obese (30 or more) |
5–9 kg (11–20 lb) |
0.17–0.27 kg (0.4–0.6 lb) |
11–19 kg (25–42 lb) |
The calculator draws your healthy range for each week — starting with 0.5–2 kg by week 13 and rising steadily to the total range at 40 weeks — and shows where you are today.
Where does the weight go?
At full term, roughly: baby 3–3.5 kg, placenta 0.7 kg, amniotic fluid 0.8 kg, bigger womb 1 kg, breasts 0.5 kg, extra blood 1.5 kg, extra fluid 1.5 kg and stored fat 2.5–3.5 kg.
Gaining too much or too little?
- Too little can raise the risk of a small baby and early birth.
- Too much can raise the risk of gestational diabetes, high blood pressure, a C-section and weight that stays after birth.
- Do not diet to lose weight during pregnancy — talk to your doctor instead, and follow a balanced pregnancy diet plan.
Note for South Asian women: the IOM ranges use the standard BMI cut-offs. Some doctors in India use lower BMI cut-offs for Asian women (overweight from 23), so ask your doctor which range applies to you.
Frequently asked questions
How much weight should I gain in the first trimester?
Usually only 0.5–2 kg (1–4.5 lb) in total. Many women gain less, or even lose a little because of nausea — that is usually fine.
How much weight should I gain per week?
In the second and third trimesters, about 0.35–0.5 kg (0.8–1 lb) a week if your BMI was healthy before pregnancy — less if it was higher, more if it was lower.
What if I am gaining too fast?
Do not try to lose weight. Look at portion sizes, sugary drinks and snacks, stay active with walking, and discuss it at your next check-up.
Sources: IOM 2009: Weight gain during pregnancy · ACOG: Weight gain during pregnancy
Reviewed for accuracy against the sources above. This page is general information, not medical advice — talk to your doctor or a registered dietitian about your own needs.
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