Tommy's PregnancyHub

Overweight and pregnant

If you are classed as overweight or obese in pregnancy based on your BMI, it’s important to manage your weight as best you can.

What exactly is ‘overweight’/'obesity' during pregnancy?

Your BMI is a measure that uses your height and weight to work out if your weight is in a healthy range. For pregnant women your BMI calculation will be based on your weight before pregnancy.

Find out your BMI

Once you work out your BMI, this is the scale:

  • Less than 18.5 = underweight
  • 18.5 to 24.9 = healthy weight
  • 25 to 29.9 = overweight
  • 30 to 39.9 = obese
  • 40 = severely obese

At your first antenatal visit, called the booking appointment, your midwife may measure your height and weigh you to work out your BMI.

Try not to be offended if anyone involved with your health care uses the words 'overweight' or 'obese' to describe your weight. A lot of women don't like these terms, but nobody is judging you. The medical experts looking after you during pregnancy may need to use them so they can make sure you have the best advice and support to help you have a healthy pregnancy. Someone who is categorised as obese, for example, will get extra advice and care.

Read about making a weight management plan here

What are the risks of being overweight and pregnant or obese and pregnant?

If you have a high BMI (over 25) before pregnancy or in early pregnancy, this can affect your health and how your baby develops. The higher your BMI the higher the risk.

These risks include:

High BMI and risks to your baby

Risks for your baby that are linked with a high BMI include:

This can be difficult to read but try not to worry. You will have extra care throughout your pregnancy and there are lots of things you can do to minimise the risks and have a healthier pregnancy.

“You can sometimes be made to feel like the worst mum in the world because you are overweight. But all that any woman wants is a healthy pregnancy and baby. So try not take it to heart or feel targeted when healthcare professionals talk about obesity, because they are just following what the guidelines say. Remember that managing your weight and making healthier food choices is useful advice for everyone in pregnancy, regardless of their size. You are making informed choices that are the best for you and your baby, just like everyone else.”

Tammy, mother of six

If I'm obese and pregnant is it too late to reduce these risks?

It’s unlikely that you can reduce all risks. But there are plenty of things you can do to make sure you have a healthier pregnancy, such as:

  • go to all your antenatal appointments, scans and make sure you have any recommended blood pressure or gestational diabetes tests
  • eat well and stay active
  • take all the recommended supplements
  • follow any specialist advice from a dietitian or anyone else involved in your care.

Should I try and lose weight while I’m pregnant?

No. Even if you are classed as obese, dieting while you’re pregnant may harm the baby. Just try and concentrate on eating well. If you do, you may not gain any weight while you’re pregnant and you may even lose a little bit. This won’t harm your baby.

What extra care will I get during my pregnancy?

If you have a BMI over 30 you should be referred to a dietitian for an assessment and advice about healthy eating and exercise.

You will also have:

  • extra ultrasound scans to check the baby’s development
  • blood pressure tests at every antenatal appointment
  • a gestational diabetes  test between 24-28 weeks (if your BMI is over 40 you may have this test earlier)
  • a risk assessment for thrombosis (blood clots in your legs or lungs) at your first antenatal appointment, which will then be monitored throughout your pregnancy.

You may also need to have injections of low molecular weight heparin to reduce your risk of blood clots.

If you have a BMI over 40 there is a higher risk of complications during labour or birth. These include:

  • a longer labour
  • premature birth (born before 37 weeks)
  • an emergency caesarean section
  • a more difficult operation if you need a caesarean section and a higher risk of complications afterward, for example a wood infection or blood clots
  • anaesthetic complications, especially with general anaesthesia
  • heavy bleeding after birth (postpartum haemorrhage) or at the time of caesarean section.

Because of these risks your obstetrician and/or midwife will talk to you about the safest way and place for you to give birth and your options may be limited. You should also be referred to an anaesthetist (a doctor who specialises in pain relief) to talk about pain relief during labour.

Being classed as obese does not always mean you will need a caesarean section but you may be more likely to have one. Find out more about c-section advice for overweight women.

Taking pregnancy supplements

Folic acid

Folic acid  helps to reduce the risks of your baby having a neural tube defect. If your BMI is 30 or above you should take a daily dose of 5 mg of folic acid. This is a higher dose than the usual pregnancy dose, so you’ll need a prescription from your doctor. Ideally, this should be taken a month before you get pregnant and until you reach your 13th week of pregnancy. If you didn’t take it before you got pregnant don’t worry, just start taking it now until you are 13 weeks.

Vitamin D supplements

All pregnant women are advised to take a daily dose of 10 micrograms of vitamin D supplement. If your BMI is over 30 it’s more likely that you are lacking vitamin D. So, it’s very important to take vitamin D supplements. 

Healthy start

Healthy Start is a UK-wide scheme that provides free vitamins and weekly vouchers for milk, plain fresh and frozen fruit and vegetables and infant formula milk.

You qualify if you are on benefits and:

  • you are at least 10 weeks pregnant
  • have children under the age of four.

All pregnant women under the age of 18 qualify – whether they are on benefits or not. To find out more and apply visit Healthy Start or call 0345 607 6823.

Eating well

Try to:

  • avoid ‘eating for two’.
  • base your meals on starchy foods such as potatoes, brown bread, brown pasta or rice that contain wholegrains.
  • eat fibre-rich foods such as oats, beans, lentils, grains, seeds, fruit and vegetables as well as wholegrain bread, brown rice and pasta
  • eat at least five portions of a variety of fruit and vegetables each day, instead of foods higher in fat and calories
  • eat a low-fat diet
  • eat as little as possible of the following: fried food, drinks and sweets/biscuits high in added sugars, and other foods high in fat and sugar
  • always have breakfast
  • watch the portion size of your meals and snacks and how often you eat.

Read more about healthy eating when you're overweight and pregnant


If you weren’t active before you got pregnant don’t suddenly start doing vigorous exercise. Start by doing no more than 15 minutes of continuous exercise 3 times a week. Increase this gradually to at least 4 30-minute sessions a week.

You can also try:

  • making activities such as walking, cycling, swimming, low impact aerobics and gardening part of your daily life
  • taking the stairs instead of the lift or go for a walk at lunchtime
  • avoiding sitting for long periods, watching television or at a computer, for example.

Read more about exercising in pregnancy if you are overweight

NHS Choices (accessed 01/02/2018) Obesity, Page last reviewed: 15/06/2016 Next review due: 15/06/2019

Royal College of Obstetricians and Gynaecologists Why your weight matters during pregnancy and after birth (Page last reviewed: Nov 2011)

NICE Guidelines (2010) Weight management before, during and after pregnancy National Institute for Health and Care Excellence

Review dates
Reviewed: 14 November 2018
Next review: 14 November 2021

This content is currently being reviewed by our team. Updated information will be coming soon.