Tommy's PregnancyHub

Overweight and fertility when planning a pregnancy

Being a healthy weight helps with fertility, pregnancy and the future health of the child.

Being a healthy weight is helpful if you are planning to have a baby. Your BMI (Body Mass Index) is a measure that uses your height and weight to work out if your weight is in a healthy range. 

Having an overweight or underweight BMI can affect your fertility, cause health problems during pregnancy and affect the future health of a child. If you have a high BMI bringing it down, even by 1 or 2 points, can make a difference.

Note: This page covers high BMI (overweight). If you have a low BMI (underweight), there is information here for you.

On this page

Higher dose of folic acid

BMI calculator

Effect of a high BMI on fertility

Effect of a high BMI on pregnancy

Making a plan to lose weight

More support

Higher dose folic acid

If your BMI is above 30 (check with the BMI calculator underneath), you are advised to take a higher dose of folic acid of 5mg.

Folic acid prevents neural tube defects in the baby, such as spina bifida. Taking it before you conceive builds the level of folic acid up in your body to the level where it is most able to prevent this condition.

The usual folic acid dose is 400mcg. This is the dose that is in the tablets you can get in pharmacies, supermarkets and it is the dose in most of the pregnancy vitamin tablets that are available. If you have a BMI of 30 or above you are advise to take 5 mg per day. This needs to be prescribed by your doctor, so make an appointment as soon as you start planning a pregnancy.

BMI Calculator

BMI calculator

Your height
Your pre-pregnancy weight

Generally, people involved in your health care will describe your BMI as follows:

  • 18.5 or lower = underweight
  • Between 18.5 and 24.9 = healthy weight
  • Between 25 and 29.9 = overweight
  • 30 or higher = obese.

Effect of a high BMI on fertility

Having a high BMI can reduce your chances of getting pregnant. The ideal BMI for getting pregnant is between 18.5 and 24.9. This is known as the healthy range. If you have a high BMI, bringing it closer to the healthy range before trying for a baby will help you get pregnant as well as improving the health of your future pregnancy and child.

If you have a very high BMI you may feel like it is an impossible task to reach the healthy range and you may have been struggling with your weight your whole life. Try not to lose heart, even bringing your BMI a few points down the scale can make a difference. If your BMI is over 30, for example, bringing it down to 28 will really help.

Men, fertility and weight

Having a high BMI can also affect the quality and quantity of men’s sperm, which can also contribute to fertility problems. Find out more about men’s health. 

Effect of a high BMI on pregnancy

High BMI and risks to pregnancy

Having a high BMI gives you more risk of problems in pregnancy. The higher your BMI, the greater the risk, so bringing your BMI down by 1 or 2 points before pregnancy can really help. Once you are pregnant it is not recommended that you go on a diet that limits specific types of food. That is one of the reasons why it is better to lose weight before you get pregnant if possible.

If you have a BMI of 35 or above at the start of your pregnancy, your risk of pre-eclampsia (a pregnancy condition that can be dangerous for mother and baby) is double that of a woman who has a BMI under 25.

Other pregnancy problems that are more likely if you have a high BMI are:

If your BMI is over 30 when you get pregnant you may have more antenatal appointments (visits to the midwife) during your pregnancy because of the higher risk of problems. You may also be advised against some birth choices, such as a home birth.

High BMI and risks to baby

If you have a high BMI before pregnancy or in early pregnancy, this can affect the way your baby develops.

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

If you have a high BMI, bringing it down, even by one or two points, can help you to have a healthy pregnancy and baby. The closer you are to a healthy weight, the more likely you are to have a healthy pregnancy.

Making a plan to lose weight

The best way to get closer to a healthy weight is to eat a healthy, reduced-calorie diet and to become more active.

Download and print our Weight Management Goal Plan

It will help you set some goals that you can follow and you can pin it somewhere you will see it every day.

People who have step-by-step plans to help them reach a goal are more likely to succeed. Pick some practical things you can do today, such as going for a walk, planning a healthy shopping list or signing up for a pregnancy exercise classes. If your plan is clear and simple it is easier to stick to it.

Give yourself goals you can achieve

Start by picking the easiest things to change and make the changes very simple. For example, you could say, 'I will have a healthy breakfast every day instead of skipping breakfast.' Or 'I will take a healthy snack to work instead of buying a chocolate bar.' If you know exactly what you're aiming to do, it will be much easier to stick to than a vague idea that you'll be 'healthier'.

Write your goals on the goal plan and tick them off when you've done them.

Think about why you're eating

It’s tempting to reach for the biscuit tin when we've had a bad day or when we’re bored. You may also be used to having a snack at a particular time of day so it feels as though you’re missing out if you don't have it, even if you're not hungry.

If you're aware of why you're eating, that's a big step towards taking control of eating when you're not hungry. Ask yourself whether you're really hungry and if you are, eat something. If you're not hungry, or you're not sure, you may be thirsty or need something to distract you.

Find a distraction

If you crave food when you know you're not really hungry, try doing something to distract yourself. You could:

  • phone a friend
  • go for a walk
  • get a glass of water or a mug of fruit tea
  • have a warm bath, go for a walk
  • put some music on
  • read a book.

It doesn't matter what you do as long as it takes your mind off eating. 

Get active with a friend

If you know someone who is pregnant, or trying to manage their weight, get together to walk, swim or exercise class. You're more likely to stick to your healthy goals if you do them with someone else and you'll be able to give each other support. Getting active with a friend is a great excuse to meet up for an activity, a healthy lunch or just a chat.

Join a club

Joining Weight Watchers or another slimming club is a good idea as it has been shown to help people lose weight. A good weight-loss programme will not deprive you of nutrition and it should:

  • look at why you might find it hard to lose weight
  • fit around your needs and choices
  • be sensitive to your weight concerns
  • be based on a balanced, healthy diet
  • encourage regular physical activity (exercise)
  • aim to lose no more than 0.5–1 kg (1–2 lb) a week.

Don't give yourself a hard time

Everyone has days where they just don't feel like doing much or when they eat the biscuits they said they wouldn't have. If this happens to you, try not to get annoyed with yourself or feel that you have failed.

Believe in yourself and tell yourself that tomorrow is a new day. You can do this, for you and for your baby.

Reward yourself!

It feels great to succeed at a goal you've set yourself. For many people, that feeling is enough to stay on track but you could also reward yourself when you stick to your plan. Choose treats that aren't food, such as a bubble bath, a magazine or b, a manicure, haircut or a movie. A reward is a great reason to keep going.

Follow these tips

  1. Eat a healthy, balanced, calorie-controlled diet
  2. Be physically active, doing activities, doing activities such as fast walking, jogging, or swimming for 150 to 300 minutes a week (for example 30 minutes a day)
  3. Eat slowly and be aware during times where you could be tempted to overeat, such as eating out or all-you-can-eat buffets
  4. Avoid sitting for long periods of time – this is bad for you before, during and after pregnancy
  5. Start the day well with a sugar-free breakfast.

Speak to your GP if you need more advice about lifestyle changes and how to improve your diet. You may be referred to a dietitian if you need more help to lose weight.

Use an app

  • Try the NHS Couch to 5k or the Active 10 app, which has helped thousands of people with a high BMI to become active.
  • When you are shopping use the NHS food scanner app, which shows quickly and easily how much sugar, sat fat and salt is inside your food and drink. It gives a friendly thumbs up to healthier foods.

More support

NHS Choices provides information on healthy eating, losing weight and eating disorders. You can also find weight loss support groups in your area on the website.

Hoop UK is a charity that supports people with issues surrounding weight management and obesity. 
0303 300 0314

 Are you ready to conceive? Use our tool to find out.

  1. Sue Macdonald and Gail Johnson Mayes’ Midwifery, Edinburgh: Baillir̈e Tindall Elsevier, 2017
  2. RCOG (2018) Care of Women with Obesity in Pregnancy (Green-top Guideline No. 72)
  3. NICE Guidelines (2010) Weight management before, during and after pregnancy, National Institute for Health and Care Excellence
  4. Clinical Knowledge Summaries (Aug 2017) Pre-conception advice and management
  5. NHS Choices (accessed 01/02/2018) How can I improve my chances of becoming a dad? Page last reviewed: 24/07/2017 Next review due: 24/07/2020
  6. NHS Choices (accessed 01/02/2018) Obesity, Page last reviewed: 15/06/2016 Next review due: 15/06/2019
  7. Royal College of Obstetricians and Gynaecologists Why your weight matters during pregnancy and after birth Page last reviewed: Nov 2011
  8. Gudzune, Kimberly A, et al Efficacy of commercial weight loss programs: an updated systematic review, Annals of Internal Medicine 2015 Apr 7; 162(7); 501-512 
  9. Khaodhiar L, Blackburn GL. Health benefits and risks of weight loss. In: Bjorntorp P, ed. International Textbook of Obesity. Chichester, England: John Wiley & Sons; 2001:413-439.
  10. Heshka S, Anderson JW, Atkinson RL, et al. Weight Loss With Self-help Compared With a Structured Commercial ProgramA Randomized Trial. JAMA. 2003;289(14):1792–1798. doi:10.1001/jama.289.14.1792
Review dates
Reviewed: 05 June 2018
Next review: 05 June 2021

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