Questions about weight in pregnancy

Here we’ll answer some of the common questions about your weight in pregnancy, including how much you should be eating and why this is important.

This information is for pregnant people. If you’re not pregnant yet, you can read our information about being overweight or underweight and planning a pregnancy.

Most people will put on some weight during pregnancy. This is because they are carrying the extra weight of the baby, the placenta and the amniotic fluid. Managing your weight in pregnancy will help you and your baby's health, both now and in the future. 

What is healthy for you depends on lots of factors, including your weight before pregnancy. The most important thing you can do is focus on eating healthy food and staying active

How is my weight in pregnancy measured?

At your first antenatal visit (the booking appointment) your midwife will measure your body mass index (BMI). This is a measure that uses your height and weight to work out if your weight is healthy and will be based on your weight before pregnancy.

If you have a high or low BMI you will get extra advice and care during your pregnancy.

BMI is not a perfect way to measure your weight because it cannot tell the difference between excess fat, muscle or bone. But it is still the best way of assessing your weight medically.

BMI weight ranges

The BMI weight healthy range is different for different ethnicities.  

People with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background have a higher risk of developing some long-term conditions, such as type 2 diabetes, with a lower BMI.  

If you are in these groups a BMI:

  • below 18.5 is underweight
  • between 18.5 and 23 is healthy  
  • over 23  means increased risk (overweight)
  • over 27.5 means high risk (obese).

For people of White heritage, a BMI:

  • below 18.5 is underweight
  • between 18.5 and 24.9 is healthy
  • between 25 and 29.9 is overweight
  • of 30 or over is obese.

Why does the BMI calculation change for different ethnic groups?

The BMI definition of obesity (a BMI of 30+) was originally developed using data mostly from White populations. Since then, research has found that people from a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, have a higher risk of developing some long-term conditions, such as type 2 diabetes, when they have a lower BMI.

As a result, the NHS has developed guidelines to make sure that people from these ethnic backgrounds get help to prevent developing type 2 diabetes earlier than people from White backgrounds.

There is not enough evidence yet to say whether people from different ethnic backgrounds should have different pregnancy care based on their weight.

This means that the advice and care you will have about your weight in pregnancy is the same for all women and birthing people, whatever your ethnic background.

Find out your BMI.

Why is my weight important to my pregnancy?

Being either overweight or underweight may increase your risk of pregnancy complications. But there are things you can do to reduce the risks and you will get extra support from your healthcare team.

Managing your weight by eating well and staying active can help you have a healthier pregnancy and a safer birth.

If you are underweight making sure you gain weight healthily can also help you reduce the risks of some health problems for you and your baby.  

Read more about how to have a healthier pregnancy if you are overweight and pregnant, and if you are underweight and pregnant.

How much weight should I put on in pregnancy?

There are no official guidelines for how much weight you should gain in pregnancy in the UK. That’s because everyone is different, and the weight you gain is made up of lots of different things, not just your baby or your body fat. 

The key thing is to keep your weight gain at a safe and healthy level for you and your baby. Your midwife will be able to advise and support you with this. Find out more about healthy weight gain in pregnancy.

What is the average weight gain in pregnancy?

Most people put on between 22lb (10kg) and 28lb (12.5kg). That’s mostly in the second half of their pregnancy.

Your healthy weight gain during pregnancy may depend on your BMI before you got pregnant. 

Should I be eating for 2?

You do not need to eat any extra food during the first 6 months of pregnancy. After that, you only need an extra 200 calories a day. This is roughly half a sandwich. Find out more about healthy and satisfying 200-calorie snacks.

Just make sure you eat a healthy, balanced diet, which will help you and your baby to get all the nutrients you need.  

There’s no need to ‘eat for 2’ or drink full-fat milk. Try not to let well-meaning family and friends persuade you to have any extra helpings. And only eat foods that are high in sugar or fat, such as sweets, crisps and biscuits, as rare treats.

Find out more about how much you should be eating in pregnancy.

Can I try to lose weight while I’m pregnant?

Do not diet or try to lose weight while you're pregnant as this is not healthy for you or your baby. You may both miss out on nutrients that you need to stay healthy and strong.

If you have a high BMI, the health professionals looking after you will help you take steps to eat well and reduce the risks to you and your baby. Your doctor or midwife should also refer you to a dietitian. You can also ask what weight-management programmes there are for pregnant women in your area.

If you are pregnant and have an eating disorder, or have had one in the past, it’s important to speak to your healthcare team about it. They can offer you extra support during pregnancy and may refer you to a nutritionist, dietitian or a specialist in eating disorders.

Read more about eating disorders in pregnancy.

Why am I losing weight during pregnancy without pregnancy-related (morning) sickness?

Some people may lose some weight if they have morning sickness. Even if you are feel or are being sick, try to eat small, frequent meals of plain foods that are high in carbohydrate and low in fat (such as bread, rice, crackers and pasta). Find out more about pregnancy sickness and how to manage it.

Talk to your midwife if you are losing weight during pregnancy, with or without morning sickness.

So, what can I do if I’m underweight or overweight when I’m pregnant?

Lots of people worry about their weight during pregnancy, but there are practical things you can do to stay well.

Focus on being as healthy as you can and aim to have a balance of different foods. This will be good for you and your baby and it will prevent too much weight gain. It may also make it easier to lose weight after you have the baby.

Staying active during your pregnancy will boost yours and your baby’s health, as well as help with managing your weight.

Find out more about being underweight or overweight in pregnancy.

How do I lose weight after pregnancy?

Your body has just been through a challenging experience, and you’ll probably feel sore and bruised. It may take a while to recover, so make sure you take things slowly and talk to your midwife or health visitor if anything worries you. Find out more about your body after the birth.

NHS. Weight gain in pregnancy. (Page last reviewed: 06 July 2022. Next review due: 06 July 2025)

NICE (2010). Weight management before, during and after pregnancy: Public health guideline 27. National Institute for Health and Care Excellence

NHS. BMI healthy calculator. (Page last reviewed: 29 March 2023 Next review due: 29 March 2026)

Rishi Caleyachetty, PHD et al (2021) Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in Engand: a population-based cohort study. The Lancet Diabetes & Endocrinology

NICE (2022). Obesity: identification, assessment and management. National Institute for Health and Care Excellence

Royal College of Obstetricians and Gynaecologists. (2022) Being overweight in pregnancy and after birth: patient information leaflet. 

Burnie R, Golob E, et al (2022) Pregnancy in underweight women: implications, management and outcomes. TOG 2022;24:50-7. doi: 10.1111/tog.12792

Review dates
Reviewed: 05 July 2023
Next review: 05 July 2026