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.
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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.
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:
- thrombosis (blood clots)
- gestational diabetes (diabetes in pregnancy)
- premature birth (where the baby is born before they are fully developed)
- a longer labour
- emergency caesarean section
- heavy bleeding after birth.
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:
- premature birth (where the baby is born before they are fully developed)
- baby having a high birth weight
- obesity and diabetes in their later life.
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
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.
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 book, a manicure, haircut or a movie. A reward is a great reason to keep going.
- Eat a healthy, balanced, calorie-controlled diet
- 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)
- Eat slowly and be aware during times where you could be tempted to overeat, such as eating out or all-you-can-eat buffets
- Avoid sitting for long periods of time – this is bad for you before, during and after pregnancy
- 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.
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
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ℹLast reviewed on June 5th, 2018. Next review date June 5th, 2021.