Pregnancy and baby

Overweight and pregnant

How much weight should I put on during pregnancy?

Media last reviewed: 20/03/2014

Next review due: 20/03/2016

Being very overweight, or obese, which is usually defined as having a body mass index (BMI) of 30 or over, is increasingly common. Around 15-20% of pregnant women are now in this category. Your BMI is a measurement of how overweight you are and is calculated using your weight and height.

Before you get pregnant, you can use the BMI healthy weight calculator to work out if you are overweight. However, once you're pregnant, this may not be accurate.

If you are overweight, the best way to protect your health and your baby's wellbeing is to lose weight before you become pregnant. By reaching a healthy weight, you increase your chances of conceiving naturally and reduce your risk of the problems associated with being overweight in pregnancy.

Contact your GP for advice on how to lose weight. Your doctor may be able to refer you to a specialist weight loss clinic. Find out about losing weight before you become pregnant.

If you get pregnant before losing weight, try not to worry – most women who are overweight have a straightforward pregnancy and birth, and have healthy babies. However, being overweight does increase the risk of complications for both you and your baby. Good antenatal care can help to minimise these risks.

During pregnancy 

If you are very overweight and pregnant, don't try to lose weight during your pregnancy, as this may not be safe. There is no evidence that losing weight while you're pregnant will reduce the risks.

The best way to protect your health and your baby's health is to go to all your antenatal appointments so that the midwife, doctor and any other health professionals can keep an eye on you both. They can manage the risks that you might face due to your weight, and act to prevent – or deal with – any problems.

It's also important to eat a healthy, balanced diet and get some physical activity every day. You should be offered a referral to a dietitian or other health professional for personalised advice on healthy eating and how to be physically active during your pregnancy. Being physically active in pregnancy will not harm your baby.

Read about how to have a healthy diet while pregnant.

Eating and exercise

Eating healthily (including knowing what foods to avoid) and doing activities such as walking and swimming is good for all pregnant women. If you weren't active before pregnancy, it's a good idea to consult your midwife or doctor before starting a new exercise regime when you're pregnant.

If you start an aerobic exercise programme (such as swimming, walking, running or aerobics classes), tell the instructor that you're pregnant and begin with no more than 15 minutes of continuous exercise, three times a week. Increase this gradually to daily 30-minute sessions.

Remember that exercise doesn't have to be strenuous to be beneficial. As a general rule, you should be able to hold a conversation as you exercise when pregnant. If you become breathless as you talk, you're probably exercising too strenuously.

Find out more about exercising while pregnant.

Your care in pregnancy

If you become pregnant before losing weight, you'll be tested for gestational diabetes. You may also be referred to an anaesthetist to discuss issues such as having an epidural during labour. You're more likely to need this type of pain relief, because very overweight women are more likely to have an instrumental delivery (ventouse or forceps or caesarean), and it can be difficult for the epidural to be given.

If you're overweight, discuss your birth options with your midwife or doctor, because there are restrictions on which women can safely deliver at home or in a birthing pool. Because overweight women are more likely to need forceps, ventouse or caesarean to give birth, it's usually safer to opt for a hospital birth, where there's faster access to medical care and pain relief options, if needed.

Find out more about your options on where to give birth.

The National Institute for Health and Care Excellence (NICE) has produced guidelines on weight management before, during and after pregnancy. It is not aimed at women who have a BMI over 30, but it has useful information on achieving, and maintaining, a healthy weight.

Risks of being overweight in pregnancy

Being overweight increases the risk of complications for pregnant women and their babies. The higher a woman's BMI, the higher the risks. The increasing risks are in relation to:   

  • miscarriage  the overall risk of miscarriage under 12 weeks is one in five (20%); if you have a BMI over 30, the risk is one in four (25%)
  • gestational diabetes  if your BMI is 30 or above, you are three times more likely to develop gestational diabetes than women whose BMI is below 30
  • high blood pressure and pre-eclampsia  if you have a BMI of 35 or above at the beginning of your pregnancy, your risk of pre-eclampsia is twice that of women who have a BMI under 25
  • blood clots  all pregnant women have a higher risk of blood clots compared to women who are not pregnant, and if your BMI is 30 or more the risk is additionally increased  
  • the baby's shoulder becoming "stuck" during labour (sometimes called shoulder dystocia)
  • heavier bleeding than normal after the birth  
  • having a baby weighing more than 4kg (8lb 14oz)  the overall risk of this for women with a BMI between 20 and 30 is 7 in 100 (7%); if your BMI is over 30, your risk is doubled to 14 in 100 (14%)

You are also more likely to need an induction and instrumental (ventouse or forceps) delivery, and an emergency caesarean section.

Problems for your baby can include being born early (before 37 weeks), and an increased risk of stillbirth (from an overall risk of 1 in 200 in the UK to 1 in 100 if you have a BMI of 30 or more). There is also a higher risk of foetal abnormality, such as neural tube defects like spina bifida. Overall, around 1 in 1,000 babies are born with neural tube defects in the UK. If your BMI is over 40, the risk is three times the risk of a woman with a BMI below 30.

These problems can also happen to any pregnant woman, whether she is overweight or not.

Bear in mind that although these risks are increased if your BMI is 30 or over, most women who are overweight will have a healthy baby.

You can find out more in a leaflet from the Royal College of Obstetricians and Gynaecologists, called Why your weight matters during pregnancy and after birth.

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Media last reviewed: 11/07/2015

Next review due: 11/07/2017

Page last reviewed: 18/03/2015

Next review due: 18/03/2017


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The 17 comments posted are personal views. Any information they give has not been checked and may not be accurate.

mrskdawson said on 22 November 2014

I am 21st and 20 weeks pregnant. I also attend a slimming world class and have lost 2st. I also attend a healthy lifestyle meeting with a nutritionist midwife who weighs me every 4 weeks ad she explained even though there are risks does not mean they will happen to me or my baby. I was so scared I told my consultant that I would probably be better just having a section and she told me there is no reason I can't have a normal delivery. I am being closely monitored anyway because my son was born premature because of lack of blood flow through the placenta, fingers crossed everything goes well this time.

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Bushy26 said on 28 August 2014

I think this BMI stuff is relly confusing, misleading and worry us women way too much. I'm not saying not on the BMI worry band wagon, but I had a BMI of 31 before I was pregnant and weighing in at 12 st (approx) 5ft 3inches and wearing a size 12. I admit I was carrying excess and this pregnancy was unexpected, but now because I am actually put in the obese range, I worry and obsess all the time that I am overweight and constantly think of ways to safely lose/control my weight while pregnant so not to harm my baby. I am currently in a size 12 maternity at 18 weeks.

I hope this puts some of you at ease about all of this, just eat unprocessed foods where you can and do the minimum walks of 30 mins per day and you will be golden :)

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krazykay90 said on 11 August 2014

Hi everyone,
I was 18 and a healthy weight and size 10 with my first pregnancy with my son now 5 however when I was 22 weeks pregnant I found out he had gastroschisis (birth defect which isn't genetic where the intestines form outside of the body)
I am now 24 and pregnant for the 2nd time and petrified as I am now unfortunately a size 16/18 with PCOS so dreading what complications could occur :(

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Hwils10 said on 29 June 2014

Hi everyone, my husband and I have been trying to conceive for over three years now... I am 11 weeks pregnant. I took my prenatal vitamins even before I found out I was pregnant. I eat healthy, all organic and I never have ready meals or takeaways. I love veggies a lot of times eat them raw! I am also apparently very obese wearing 18-20. I am only 27 and have just found out today that I am having a "delayed miscarriage". After reading this I feel like in a way I have possibly harmed my baby by being so damned selfish and being so fat. I wish more then anything to be a great mother to a healthy baby with my husband. This has really scared me and made for more guilty. Perhaps I should go on a hunger strike. I couldn't eat if I tried anyway.

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Garnier13 said on 08 March 2014

hi I have read the problems they he put about getting pregnant while overweight and obese I had not problems I had a healthy boy no health issues with me while pregnant I think they scare people too much with the so called facts you can still have a healthy child with having weight problems.

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carlyh92 said on 12 January 2014

After my first baby I put on a lot of weight. I was a size 12, then went up to an 18 after he was born. I'm now and 18 to 20 and in the early stages of pregnancy with my second baby. This article has really put the spooks in me, and I'm so scared that I'm harming my baby.
I couldn't bring myself to read the part about miscarriages, as I'm petrified of this anyway, without adding extra worries!
They say don't lose weight, but don't be fat!

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AMFISHER said on 15 December 2013

Hi all, I too read this page when I found out I was expecting my first child. Like many of other mothers it scared me and I was upset thinking I was somehow going to endanger my baby as well as myself. Well I'd just like to say to all the curvy mothers out there like myself, (although each pregnancy is different) I had a fantastic pregnancy from start to finish, and gave birth to a wonderfully healthy 7lb 1oz baby girl (when I became pregnant I was a size 16). I did not suffer any sort of health problems, diabetes, high blood pressure etc, I was in fact the picture of health. The only unpleasant part of my pregnancy was the rudeness of both sonographers basically telling me my 'jellybelly' to quote one of them, was making the scan difficult. Don't worry about your BMI eat healthy, go for a walk and enjoy the most wonderful experience of your life!

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sparkles123 said on 30 October 2013

I just wanted to say that I was a size 26 an nearly 19 stone when I got pregnant with my first child and I had a perfectly fine pregnancy with no health worries. This article really does make it sound like if you're pregnant and overweight then you're doomed. I just wanted to bed my twopence worth and say that for me, it was issue free!

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chandlercampbell said on 17 November 2012

I am a size 20 and 8 weeks pregnant. I am now really frightened after reading this article. I raised my concerns with my GP and my doctor said I am fit and healthy with good blood pressure and not to worry but now I am really worrying. Should I try to lose weight whilst pregnant as I don't want to harm my baby?

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chunkypickle said on 15 August 2012

I think this article needs some actual figures so that I can make an informed decision. For instance:

More than half of women who die during pregnancy are overweight or obese

It is estimated that 60% of the UK population is overweight or obese, so that's not an increase at all - what is the actual difference?

'Increased Risk' needs to be quantified is it increasing 50% from a 1% risk or a 50% risk (ie. 1% vs 2% and 50% vs 75%)? Is it increasing 10% from a 1% or a 50% risk (ie. a 1% vs1.1% and 50% vs 55%)?

Without figures, or sources for these assertions this is just fear-mongering and pushing guilt and stress on overweight pregnant women - stress, you know that thing which is also proven to increase the risk of all sorts of problems - although you actually provide figures for those:

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User704856 said on 15 August 2012

It is totally crass to allow comments on this site without giving balanced replies from experts. The above postings show how mis-information can be spread.

As the article above states, being obese increases the risk of a number of potentially serious complications, as well as from dying. It does not say that thinner people are at no risk, nor does it say that all obese mums will have complications.

This is no different from asking people to be careful before crossing a busy road.

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4mernuss said on 26 June 2012

Just checking if this works didn't last time

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4mernuss said on 26 June 2012

I have read the comments left so far and i entirely understand the emotion in them however .... this article is meant to inform and it does that. The article does not claim that only obese women have difficulties in pregnancy there are other risk factors for women , many others in fact - it is one of the most hazardous things a woman will ever do in her life regardless of her size. This article outlines the specific complications obesity can cause and the ones that midwives and gynaecologists have to be on the lookout for in order to keep mom and baby healthy. Would you prefer it if they acted as if there were no additional risk factors for overweight mothers to be and did no additional scans or checks to make sure all was well? Would you prefer if they left it all to chance and luck of the draw? I think not. If they did that and things went wrong would you accept as an answer to your 'why' - ' well that's just what happens sometimes' ? Of course not . The health of a mother directly affects the health of the baby - that's not prejudice, that's biology and it is your Drs responsibility to point that out and by extension the responsibility of the NHS to educate people . There are degrees of obesity and ill health or good health even in the overweight and the healthier you are other than being overweight the better it is for your baby obviously . This isn't just plucked out of the air I am a retired nurse and mother of 5 and I know a thing or three about how to keep healthy in pregnancy and how that benefits the foetus/baby. Don't get mad ladies - get healthy and enjoy your worry free pregnancy as a result .

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STEPHYKINS said on 17 February 2012

This is awful i was a size 12 and had a healthy bmi of 24 when i became pregnant with my son and i was riddled with problems the entire pregnancy so this prooves that these problems are not just to do with being overweight its to do with the woman and the pregnancy and while i was having a awful pregnancy some of the women i knew who were double my size had perfect pregnancies and this should be removed "More than half of women who die during pregnancy are overweight or obese" this is horrible and offensive and yeh its never good to be overweight but it does not mean your going to die im bigger than what i should be but im physically fit and i eat healthy alot of it is genetics it is just like the playground lets pick on the bigger people as long as your healthy and everything is in moderation is my motto but it is discusting to say that more than half of women die during pregnancy are overweight and obese and should be removed!

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xluciannex said on 13 August 2011

i can not beleive that the stuff that the nhs tell us i was a lovely size 10 when i had my daughter ate healthy all the way through pregnancy never smoked or drank alcohol,
and she was born 8lb 6oz classed as a big baby, i also had polyhydramnious, extra fluid, and got checked for diabetes and i was only a size 10.
these days i think they try to do so much research and tests it hurts the babys.
years ago there wasnt any of this, vitamins for pregnant women or anything else they do, your pregnant have your baby then get on with it, but there are a lot more still births and miscarraiges nowadays then what there was back then.
they should leave pregnant mothers and babys unless they do need help instead of scaring the life out of people.

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KAF2010 said on 12 June 2011

Oh My Goodness - that article has just really scared me.... I'm 39 have a BMI over 30 and have just found out I'm pregnant.... now I'm petrified I'm going to damage my baby :-/ but they say not to lose weight

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gemmakarim said on 22 October 2010

i think its absolutely disgusting the way women are being treat now when they are pregnant. i am 25 have 2 little girls aged 4 and 5 and am 26 weeks pregnant. i am classed as morbidly obese according to the nhs, despite being a size 14-16. i wouldnt like to know what bigger women are classed as! so now i am being made to have extra scans and gtt tests, because i am fat i am harming my baby. the nhs studies show that obese mothers are proven to have bigger babies, proven to have small premature babies, proven to get diabetes proven to be basically blamed for anything that happens during their pregnancy!! i am sure there are smaller women out there who have problems in pregnancy but nothing is said. what about disgraceful mums to be who take drugs/alcohol or smoke in pregnancy even they are treat better than the obese mothers. i think its about time someone spoke up about this, i was overweight with both my daughters and i had no problems apart from being rhesus negative, and had 2 healthy 8lbs little girls naturally.

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