Pregnancy Weight Gain Week by Week: What's Typical

Medically reviewed by: Safi Allah Khan · Written by the Momi team · Last updated 20 October 2026

This guide shows the ranges ACOG and the CDC use, a week-by-week chart for a healthy BMI, where the weight goes, and when to talk to your midwife or doctor. Weight gain is personal: use these numbers as a guide, not a goal to hit exactly.

Recommended weight gain by BMI (one baby)

ACOG and the CDC use the Institute of Medicine (IOM) 2009 guidelines, based on your body mass index (BMI) before pregnancy.

Pre-pregnancy BMI	Total gain (lb)	Total gain (kg)	Per week, 2nd and 3rd trimesters
Underweight (under 18.5)	28–40 lb	12.5–18 kg	About 1 lb (0.45 kg); range 1–1.3 lb
Healthy weight (18.5–24.9)	25–35 lb	11.5–16 kg	About 1 lb (0.45 kg); range 0.8–1 lb
Overweight (25–29.9)	15–25 lb	7–11.5 kg	About 0.6 lb (0.28 kg); range 0.5–0.7 lb
Obese (30 or more)	11–20 lb	5–9 kg	About 0.5 lb (0.22 kg); range 0.4–0.6 lb

Kilogram figures are rounded conversions. In the UK, the NHS doesn't set targets by BMI in the same way. It says most people gain 10 to 12.5 kg (22 to 28 lb), putting on most of it after week 20.

Twins

The IOM's provisional ranges for twins are higher: 37 to 54 lb (17 to 25 kg) for a healthy BMI, 31 to 50 lb (14 to 23 kg) if overweight, and 25 to 42 lb (11 to 19 kg) if obese. There isn't enough evidence to set a range for underweight twin pregnancies, so ask your provider.

Pregnancy weight gain week by week chart (healthy BMI)

This chart shows a typical cumulative range for someone with a pre-pregnancy BMI of 18.5 to 24.9, worked out from the IOM rates: 0.5 to 2 kg by the end of the first trimester, then 0.8 to 1 lb a week. It's an illustration, not a target.

By week	Typical total gain (kg)	Typical total gain (lb)
13	0.5–2 kg	1–4 lb
16	1.5–3.5 kg	3.5–7.5 lb
20	3–5 kg	7–11 lb
24	4.5–7 kg	10–15 lb
28	6–9 kg	13–19 lb
32	7.5–10.5 kg	16–23 lb
36	9–12.5 kg	19–27 lb
40	10.5–14 kg	23–31 lb

Gain isn't perfectly steady. It's normal to gain more one week and less the next, and fluid can move the scale by a kilo or more day to day. Look at the trend over several weeks.

Gain by trimester

• First trimester (weeks 1–13): often 0.5 to 2 kg in total. Some people lose a little because of nausea; Mayo Clinic notes this is common.
• Second trimester (weeks 14–27): gain picks up as your appetite returns and your baby, placenta and blood volume grow.
• Third trimester (weeks 28–40): your baby gains weight fastest now. Gain may slow slightly in the last couple of weeks.

Where the weight goes

It's not just the baby. Mayo Clinic gives this rough breakdown for a full-term pregnancy:

Part	Approximate weight
Baby	7–8 lb (3–3.6 kg)
Larger breasts	1–3 lb (0.5–1.4 kg)
Larger uterus	2 lb (0.9 kg)
Placenta	1.5 lb (0.7 kg)
Amniotic fluid	2 lb (0.9 kg)
Increased blood volume	3–4 lb (1.4–1.8 kg)
Increased fluid volume	2–3 lb (0.9–1.4 kg)
Fat stores	6–8 lb (2.7–3.6 kg)

The NHS notes that the body stores fat ready to make breast milk after birth.

Why it matters

ACOG asks providers to check your BMI at your first visit and talk to you about appropriate weight gain, nutrition and exercise, with particular attention to limiting excessive gain. The NHS explains that gaining too much weight can raise your blood pressure and increase the risk of complications such as gestational diabetes, which can lead to a larger baby, and pre-eclampsia. Gaining too little can also be a concern, which is why your provider looks at your trend and your baby's growth together rather than one number.

Healthy habits that help

• You don't need to "eat for two." For a healthy pre-pregnancy weight, ACOG says you usually need no extra calories in the first trimester, about 340 extra a day in the second and about 450 in the third.
• Choose filling, nutritious food: vegetables, fruit, whole grains, lean protein, dairy or fortified alternatives.
• Stay active if your provider says it's safe. ACOG says pregnant women should ideally get at least 150 minutes of moderate-intensity aerobic activity a week.
• Don't diet without advice. The NHS advises against dieting in pregnancy.

When to talk to your provider

Call your midwife or doctor if you:

• lose weight because you can't keep food or fluids down
• gain weight very suddenly, especially with swelling of your face, hands or feet, a severe headache or vision changes, which can be signs of pre-eclampsia
• are worried you're gaining too much or too little
• have a history of eating disorders and are finding weight changes hard

Your weight and blood pressure are usually checked at routine visits; see the pregnancy appointment schedule.

Track your weight in Momi

Momi includes a weight and health tracker, so you can log your weight through pregnancy alongside your pregnancy week by week updates. Bring your log to appointments if your provider wants to review your trend. Momi also keeps your diary, appointments and medicine reminders in one place.

Download Momi free on the App Store or Google Play. Free with ads; optional Premium.

Related: pregnancy week by week chart · baby size by week · morning sickness · How Many Weeks Pregnant Am I? · 28 weeks pregnant

Sources

• CDC, Weight Gain During Pregnancy
• ACOG, Committee Opinion 548: Weight Gain During Pregnancy
• ACOG, How much weight should I gain during pregnancy?
• ACOG, Exercise During Pregnancy
• NHS, Weight gain in pregnancy
• Mayo Clinic, Pregnancy weight gain: What's healthy?

Medical disclaimer: Momi and this website provide general information, not medical advice. Always talk to your doctor or midwife; in an emergency call your local emergency number.