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.

Weighing scales drawn in chalk on a black board.

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.[6] 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


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

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

Clinical Knowledge Summaries (Aug 2017) Pre-conception advice and management  


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    Last reviewed on October 25th, 2018. Next review date October 25th, 2021.

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    Please note that these comments are monitored but not answered by Tommy’s. Please call your GP or maternity unit if you have concerns about your health or your baby’s health.
    • By Adzee (not verified) on 25 Oct 2019 - 17:48

      I am 18weeks plus Pregnant and I already weigh 67kg.
      My question is :am I underweight or overweight?

    • By E (not verified) on 30 Oct 2018 - 12:59

      I had quite a low "healthy" BMI before getting pregnant (around 18.6) and am now at 21 weeks and have already put on 10kilos! I look slim but have a big bump! My midwife told me I should be careful not to put on too much weight, but I eat a healthy balanced diet and walk at least 1.5 hours per day. I feel worried but honestly don't know what - if anything - I should change! Thank you for your advice.

    • By Midwife @Tommys on 2 Nov 2018 - 10:48

      It is great that you are keeping a healthy balanced diet and doing regular exercise, we do not advise for you to want to lose weight or actively diet. At this stage of pregnancy you do not need to be eating any more than you normally would do pre-pregnancy. If your bump is measuring bigger than expected then your midwife may need to refer you to have a growth scan to check on the size of the baby and the amount of water around your baby.
      Best wishes
      Tommy's midwife

    • By E (not verified) on 5 Nov 2018 - 14:17

      Thank you! My bump is a normal size, and i'm eating healthily and doing exercise every day so I'm just going to try not to worry too much about my weight.. Even if it does seem like a big gain already!! I guess it's just the way it is.

    • By Liz (not verified) on 30 Jul 2018 - 22:16

      I’ve just found out im pregnant, unplanned, but a happy mistake.
      Unfortunately I suffer from binge eating disorder and have a BMI >35. I’m taking 5mg of folic acid as per RCOG. I know that there are loads of risks associated, but I feel really scared and anxious due to my size, can larger people can still have healthy babies and healthy pregnancies?

    • By Midwife @Tommys on 31 Jul 2018 - 16:02

      Hi Liz
      Yes, your weight can have an impact on your pregnancy- but that does not mean that it is always a negative impact. You may be at higher risk of certain things happening, but that does not mean that it will actually happen. Plenty of ladies who are overweight have successful pregnancies and healthy babies. You will have appointments with both your midwife and an obstetric doctor and you may be sent for a glucose tolerance test to test for gestational diabetes. Your midwife will go through all of this with you at your booking appointment (your first midwife contact.) Congratulations! Sophie,Tommy's Midwife

    • By PregnancySantander on 28 Jun 2018 - 11:13

      I am 25 weeks and have not gained any weight at all. I have had no morning sickness. Is this normal?

    • By Midwife @Tommys on 29 Jun 2018 - 11:13

      Weight gain and pregnancy symptoms can vary hugely for pregnant women. Having no sickness can be normal , no everyone experiences this in pregnancy. With regards to your lack of weight gain, this will depend on your pre-pregnancy weight, but also how you are feeling during this pregnancy, how your appetite is. If this is your first pregnancy you should be having an appointment with your midwife round about now so do have a chat with her about your concerns.
      Best wishes
      Tommy's midwife

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