Tommy's PregnancyHub

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.

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

Why is my weight important to my pregnancy?

Being outside the ‘healthy weight’ range of the BMI scale before you get pregnant can increase the risk of pregnancy problems for you and your baby.

For example, having a BMI over 30 can increase the risk of complications, such as:

Being underweight can increase the risk of complications such as: 

This can be difficult to read but try not to worry. If you have an overweight or underweight BMI your midwife and doctor will give you extra care throughout your pregnancy. There are also lots of things you can do to minimise the risks, such as staying active  and eating well.

How much extra should I eat in pregnancy?

You don’t 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 about half a sandwich. Find out more about fun and healthy 200 calorie snacks.

The most important thing is to make sure you eat a healthy, balanced diet, which will help make sure you and your baby have all the nutrients you need.

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

Everyone is different. Find out what you can do if you are underweight and need to gain weight.

What exactly is a 'portion'?

It's not just what you eat that's important, it's how much you have of it. A portion is the amount of any one type of food you eat. For example, a fruit portion would be one apple or two plums. A vegetable portion would be a small side salad. Three heaped tablespoonfuls of cooked vegetables also count as a portion. Find out more about portion size.

Is it safe to diet during pregnancy?

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

If you are concerned about putting on weight, remember that you will lose a lot of it with the birth of your baby and the placenta. And, if you have a healthy diet in pregnancy this may make it easier to lose weight after you have the baby.

Try not to worry about putting on weight. Instead, focus on being as healthy as you possibly can and aim to have a balance of different foods from the Eatwell plate. This will help keep you healthy and prevent too much weight gain.

Talk to your doctor or midwife if you have an obese BMI. You should be referred to a dietitian or ask what weight-management programmes are available for pregnant women in your area.

It's also important to stay active during your pregnancy. This will boost your and your baby’s health, as well as helping with managing your weight.

Read more about how much weight you should gain during pregnancy

NICE Guidelines (2010) Weight management before, during and after pregnancy National Institute for Health and Care Excellence https://www.nice.org.uk/guidance/ph27

Royal College of Obstetricians and Gynaecologists Why your weight matters during pregnancy and after birth (Page last reviewed: Nov 2011) www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/pi-why-your-weight-matters-during-pregnancy-and-after-birth.pdf

Clinical Knowledge Summaries (Aug 2017) Pre-conception advice and management https://cks.nice.org.uk/pre-conception-advice-and-management  

Review dates

Last reviewed: 25 October 2018
Last review: 25 October 2021