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Weight gain in pregnancy

Weight gain in pregnancy varies greatly. Most pregnant women gain between 10kg and 12.5kg (22lb to 28lb), putting on most of the weight after week 20.

Much of the extra weight is due to your baby growing, but your body will also be storing fat, ready to make breast milk after your baby is born.

Putting on too much or too little weight can lead to health problems for you or your unborn baby.

Gaining too much weight

Putting on too much weight can affect your health and increase your blood pressure.

But pregnancy isn't the time to go on a diet, as it may harm the health of the unborn child.

It's important that you eat healthily.

Gaining too much weight can increase your risk of complications.

These include:

  • gestational diabetes: too much glucose (sugar) in your blood during pregnancy can cause gestational diabetes, which increases your risk of having a large baby
  • pre-eclampsia: a rise in blood pressure can be the first sign of pre-eclampsia; although most cases are mild and cause no trouble, it can be serious

Gaining too little weight

Gaining too little weight can cause problems such as premature birth and a baby with a low birth weight (less than 2.5kg or 5.5lb at birth).

It can also mean your body isn't storing enough fat.

Lack of weight gain can be related to your diet and weight before you become pregnant.

But some naturally slim women stay slim while they're pregnant and have healthy babies.

Staying active

Staying active is important while you're pregnant, as it'll prepare your body for labour and birth.

Keep up your normal daily activity or exercise, unless you have been advised by your midwife or GP not to exercise.

Advice about your weight

Your midwife or GP may have special advice for you if you have a body mass index (BMI) of over 30 or below 18.5

If you're concerned about your weight or any other aspect of your health while pregnant, ask your midwife or GP for advice.

Video: Where does my pregnancy weight come from?

In this video, a midwife discusses where the extra weight in pregnancy comes from.

Media last reviewed: 14 March 2023
Media review due: 14 March 2026

Further information

Read the answers to more questions about pregnancy.

Page last reviewed: 6 July 2022
Next review due: 6 July 2025