Healthy weight in pregnancy

We aim to give people access to reliable science-based information to support anyone on their journey towards a healthy, sustainable diet. In this section you can read about having a healthy weight in pregnancy.

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Healthy weight in pregnancy

Everyone’s body shape during pregnancy is different and perhaps the changes occurring in your body have made you more aware of these differences. The size and position of your bump, the weight gain, or shape changes in other areas of your body, can all vary from person to person. However, being aware of your bodyweight during pregnancy is important for everyone as this can affect the health of you and your baby.

If you are thinking about becoming pregnant and you do not eat as well as you could, this is a really great time to start thinking about your diet. Making some simple positive diet and lifestyle changes can help to ensure your body is best prepared for pregnancy. For example, women entering pregnancy with a healthy weight have a lower risk of pregnancy complications and adverse outcomes compared with women who are underweight or overweight.

If you are pregnant – congratulations! This is not a time to diet or lose weight but a good time to look after yourself and your baby by eating healthily and keeping active. This can not only help you feel better but can also help you manage your pregnancy weight.

You will gain weight in pregnancy – that’s natural. But keeping your weight gain to a healthy level, by eating well and keeping active, will be good for you and your baby.

Here we have collected a few commonly asked questions about bodyweight in pregnancy.


Pregnant woman cooking and preparing food from recipe

Will I be weighed during pregnancy?

It is likely that your height and weight will be measured by your midwife at the beginning of your pregnancy (at the booking appointment, between 8 and 12 weeks of pregnancy). Your body mass index (BMI) will be calculated to work out whether you are a healthy weight for your height. Don’t worry, this is not to judge you, it is to make sure they can provide the best care and advice for you and your baby.

What is a healthy weight?

People who have a healthy weight before, or in the beginning stages, of pregnancy have a BMI of between 18.5 and 25 kg/m2:

  • a BMI of under 18.5 is classified as underweight
  • a BMI of over 25 is defined as overweight
  • a BMI of over 30 is defined as obese

What kind of complications during pregnancy are related to a larger bodyweight?

Some of these can be serious and include things like gestational diabetes, pre-eclampsia (high blood pressure), miscarriage and the need for a caesarean delivery. Health problems for your baby in the short-term and/or in later life may also be more likely. However, larger pregnant women may be able to reduce their risk of these complications by managing their weight gain during pregnancy through eating healthily, keeping active and remembering not to fall in the trap of eating for two! Remember, though, that weight loss during pregnancy is not advisable as this may harm the health of your baby.

What should I do if I’m overweight and pregnant? Is it safe to lose weight during pregnancy?

If you are a larger pregnant woman, you may have to be careful you do not gain too much extra weight during pregnancy. This is particularly the case if you had a BMI of 30 or over before you became pregnant. By eating healthily and keeping active you may be able to have a more enjoyable pregnancy, reduce the risk of complications during pregnancy and childbirth, and have a healthier baby. You may also have less weight to lose after the baby is born. However, pregnancy is not a time for dieting and losing weight. Normal weight gain in pregnancy is a result of your body changing to support the growing baby and dieting will not stop this happening. In addition, restricting your intake may mean you are not getting all the nutrients you and your baby need, and ‘crash’ diets or severely restricted diets may harm the development of your baby. Despite the risks associated with obesity in pregnancy, there is no conclusive evidence to date that losing weight during pregnancy will reduce these risks and it is important you focus on healthy eating rather than reducing your weight.

What should I do if I’m underweight and pregnant?

We often hear about overweight and obesity but being underweight can also increase some of the health risks in pregnancy. So, if you have a BMI below 18.5 you may need to put on a little more extra weight during pregnancy. You can still gain weight through eating a healthy balanced diet. For example, you may want to try eating more foods that are high in good fats, such as nuts or nut butters, fatty fish and avocados, and adding a couple of nutrient-rich snacks into your day.

How much weight should I gain during pregnancy?

All of us gain some weight when we are pregnant, but the amount of weight a woman may gain in pregnancy can vary quite a lot from person to person. Only some of this weight gain is due to increased body fat (important to protect your baby and prepare for breastfeeding). There is also the weight of the baby, placenta, amniotic fluid (the protective fluid around your baby) and the extra fluid in your blood. All these changes are important for the health of your baby. Most of this weight gain in pregnancy occurs in the second and third trimesters, with minimal weight gain in the first trimester.

The most important thing is that you do not gain too much weight as this increases your risk of complications during pregnancy (such as gestational diabetes and high blood pressure) and childbirth. Also, if you put on excess weight, you are more likely to keep this after childbirth. Therefore, gaining a healthy amount of weight is related to the best outcome for you and your baby, now and in the future.

Many pregnant women ask health professionals for advice on appropriate weight gain during pregnancy. However, there are no evidence-based UK guidelines on recommended weight gain ranges during pregnancy.

You are not likely to be weighed repeatedly during pregnancy as a matter of routine. This will only be done if it is important for the clinical management of a condition you may have or if nutrition is a particular concern.

Some reports have suggested that women gain on average between 10 kg and 12.5kg during their pregnancy, but the amount of weight gain varies from person to person. In the US, there are guidelines on weight gain in pregnancy. The US Institute of Medicine advises that if you are a healthy weight (BMI 18.5-25) at the start of pregnancy, you should put on between 11.5 and 16kg over the course of your pregnancy. Women who are heavier at the start of pregnancy should put on less weight. Overweight women (BMI between 25–30) should gain 7–11.5kg, and obese women (BMI greater than 30) should only put on 5–9kg. Remember the figures are only guidelines and are based on low quality studies in the US, and it is not known whether they can apply to other population groups in other countries. If you are concerned that you are gaining too much or too little weight, then talk to your midwife or GP.

I’m expecting twins, how much weight should I gain during pregnancy?

Like with single baby pregnancies, health authorities in the UK do not feel there is enough evidence to define a range for acceptable weight gain during pregnancy with twins. However, as a guide, the table below gives the recommendations for weight gain during pregnancy with twins for women in the US. Remember the figures are only guidelines based on low quality studies in the US and it is not known whether they would apply to other population groups in other countries. If you are concerned that you are gaining too much or too little weight, then talk to your midwife or GP.

US recommended total weight gain during pregnancy with twins, based on pre-pregnancy BMI (Institute of Medicine, US, 2009)

Pre-pregnancy BMI (kg/m2)  Total weight gain range (kg)
less than 18.5 (underweight) insufficient data
18.5-25 (healthy weight) 16.5-24.5
25-30 (overweight) 14-22.5
more than 30 (obese) 11-19

How can I make sure the amount of weight I gain is healthy?

To avoid putting on excess weight during pregnancy, try to make healthy food choices and keep active. The basic principles of a healthy diet stay the same during pregnancy. You should try to eat a diet that is:

  • based on starchy foods (choosing wholegrain varieties where possible)
  • includes plenty of fruit and vegetables (try and eat a variety)
  • includes moderate amounts of lean meat, fish (try and include one portion of oily fish per week), and other protein sources like eggs, beans and other pulses
  • includes moderate amounts of dairy products, such as milk, yogurt and cheese (choose lower fat and lower sugar varieties where possible)

Only eat limited amounts of foods and drinks that are high in fat and sugar, such as sweets, cakes, chocolate, sugar-sweetened drinks and fried foods.

For more information on a healthy diet during pregnancy read our page on nutrition during pregnancy.

Exercise during pregnancy can have great benefits for you and your baby, including decreasing your risk of pregnancy complications such as gestational diabetes and pre-eclampsia. For more information on the benefits of exercise during pregnancy, and which types of exercises you may wish to try, read our page on physical activity in pregnancy.

Should I be eating for two?

The idea of eating for two during pregnancy is a myth. In fact, your energy requirements during the first and second trimester are no different to normal as your body makes some adaptations to help reduce the extra energy it might otherwise need. However, in the last 12 weeks of your pregnancy you do need a little extra energy – about 200kcal more per day. You may find at this stage that your bump is pressing on your stomach and intestines making it difficult to eat large meals. If this is the case for you, you may find that eating smaller meals and snacks more often is a better way to get all the food you need. However, you will need to make sure that these are nutrient-rich so that you are getting all the essential vitamins and minerals that you and your growing baby need. Below are some healthy snack ideas, which are all about 200kcal.

How can you get the extra 200kcal a day you need in the last 12 weeks of pregnancy?

  • Banana shake with 1 banana, semi-skimmed milk and low-fat yogurt
  • Oatcakes with reduced fat cheddar or sardines and slices of tomato
  • Wholegrain toast with peanut butter
  • Porridge with semi-skimmed milk and a spoon of raisins
  • A small handful of unsalted mixed nuts
  • Low-fat yogurt with large fruit salad or with berries and seeds
  • Medium bowl of wholegrain cereal with semi-skimmed milk
  • Houmous with half a pitta bread, carrot and red pepper sticks
  • Cheese on toast (made with reduced fat cheddar and mustard on granary bread)

Instead of an extra snack, you may prefer to eat a slightly larger portion for lunch or dinner. For example you could add either:

  • an extra portion of boiled egg noodles and stir-fried vegetables
  • half a chicken breast, grilled without skin and 200g of steamed mixed vegetables

I feel like I want to eat more frequently, is it OK to snack?

During pregnancy, you may prefer to eat smaller meals at mealtimes with snacks in-between. You may find this helps with feelings of nausea at the beginning of pregnancy or with heartburn, common in late pregnancy. Snacking, or eating often, can be part of a healthy diet, provided you do not consume too many calories over the day, and you choose a healthy balance of foods and drinks. It’s best not to include too many foods high in saturated fat, salt and sugar. Instead, opt for foods high in fibre, starchy carbohydrates, fruit, and vegetables.

I’m suffering with morning sickness and struggle to keep food down, will this harm my baby?

Nausea and vomiting in pregnancy are usually called 'morning sickness', but it can happen at any time of the day. Although this can be worrying and unpleasant, it is a normal part of pregnancy and is unlikely to cause problems in the longer term. It usually settles by 12-14 weeks, although in some women it may last longer. Listen to your body and eat when you can. Some people find eating carbohydrate rich foods helps to curb the feelings of nausea. Eating small amounts regularly throughout the day may also help (cold meals may be more easily tolerated if your nausea is smell-related). You might even want to try having some crackers or biscuits on your bedside table, so that you can eat something before you get up. Also, try your best to replace the fluids that are lost when you are sick.

Some women do experience very severe nausea and vomiting during pregnancy (known as hyperemesis gravidarum) and in this case should consult their GP or midwife, as this can lead to dehydration (excessive loss of water and salts from the body) and serious weight loss. For more information on nausea and vomiting during pregnancy read our page on common concerns during pregnancy.

My bump seems small/big compared to other pregnant women. Should I be worried?

Bumps come in all different shapes and sizes! There are lots of different things that can affect the size of your bump including your height, weight before pregnancy, your ethnicity and how many children you have had. Your midwife will measure the size of your bump at your antenatal appointments to see if you are within the normal range.

How can I lose that post-baby weight? Will breastfeeding help me to lose weight?

Women are encouraged to breastfeed but are advised against ‘dieting’ while breastfeeding. Rather the advice is to eat healthily. For breastfeeding women, losing weight by eating healthily and taking regular exercise will not affect the quantity or quality of their milk.

Women who exclusively breastfeed for the first 6 months may require an additional 330kcal a day, but this may differ from person to person. You may need to eat a little more than usual to meet the higher energy requirements of breastfeeding, but your body will also use up the fat stored during pregnancy for this exact purpose. Breastfeeding uses these fat stores and requires extra calories. Exclusively breastfeeding is linked to a greater amount of weight loss after pregnancy and breastfeeding for a longer period is associated with a healthier BMI in the long term. Breastfeeding can also have many other health benefits for mother and baby, including helping an infant's immune system, and reducing a mother's chance of breast cancer.

Being less physically active at this time and increasing calorie intake above the extra required for breastfeeding may help to explain why some breastfeeding mums do not return to their pre-pregnancy weight.

As well as perhaps contributing to getting back to your pre-pregnancy weight faster, breastfeeding also has many other benefits for you and your baby. For example, there is growing evidence that it can help reduce the risk of your baby becoming overweight or obese in the future.

Mum breastfeeding her baby

Should I wait until I lose weight before having another baby?

If you have become overweight or obese, then getting back to a healthy weight would be better for your own health and that of your next baby.

I have lost a lot of weight recently and I’m now underweight. Should I wait until I have regained some weight before having another baby?

If you are now underweight (BMI under 18.5), then bringing your weight up to be within the normal range is preferable (BMI 18.5–25). Ideally, it is better to be at a stable, healthy weight before you become pregnant again.


Information reviewed June 2015

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