Weight gain in pregnancy basics

Much of the weight you gain during pregnancy is due to your baby. This extra weight comes to around 11.3-16kg (25-35lb). Gaining some weight during pregnancy is just part of the process. Eating the right foods and staying active will help ensure you gain a suitable amount of weight. Talk to your midwife, doctor, or a registered dietitian if you need help with planning a healthy diet during pregnancy.

How much weight gain in pregnancy is normal?

First and foremost, you need to accept that you are going to put on weight during pregnancy. You are supposed to. Your body is growing and changing to give your baby the best start in life.

By the time you come to give birth, you'll be carrying quite a cargo! Just over a third of your extra weight will come from your baby, the placenta and the amniotic fluid, and expanded blood volume (HC 2014). Here is an idea of roughly how much each one weighs:

• At birth, a baby weighs about 3.3kg (7.3lb).
• The placenta, which keeps your baby nourished, weighs 0.7kg (1.5lb).
• The amniotic fluid, which supports and cushions your baby, weighs 0.8kg (1.8lb).

But what about the rest of the extra weight? This is because of the changes that happen to your body while you're pregnant. Again, these figures are only averages:

• The muscle layer of your uterus (womb) grows a lot. It weighs an extra 0.9kg (2lb).
• Your blood volume increases and weighs an extra 1.2kg (2.6lb).
• You have extra fluid in your body, weighing about 1.2kg (2.6lb).
• Your breasts weigh an extra 0.4kg (0.9lb).
• You'll store fat, about 4kg (8.8lb), to give you energy to breastfeed.

By the end of the pregnancy you may weigh about 12.5kg (27.6lb) more than you did before you became pregnant. Remember, this is only a rough idea. Let our pregnancy weight gain tool work out your figures for you.

What is my body mass index and how will it change?

Your body mass index (BMI) measures your weight in relation to your height. It is one way of telling whether your weight is in a healthy range. Thought it’s not an exact science, it can be a useful way to get an idea of whether your weight gain is healthy. The amount of weight you should put on will depend on what your BMI was before you were pregnant (HC 2014).

You can work out your BMI using our tool. You'll need to enter the weight that you were before you conceived.

There are some guidelines as to how much weight you should gain during pregnancy, in Canada. They depend on your BMI (body mass index) before you were pregnant.

See our table below for details:

Pre-pregnancy BMI	BMI	Total weight gain	Rates of weight gain 2nd and 3rd trimester (average range/week)
Underweight	Less than 18.5	13kg to 18kg (28lb to 40lb)	0.5kg to 0.6kg (1lb to 1.3lb)
Normal weight	18.5 to 24.9	11kg to 16kg (25lb to 35lb)	0.4kg to 0.5kg (0.8lb to 1lb)
Overweight	25 to 29.9	7kg to 11kg (15lb to 25lb)	0.2kg to 0.3kg (0.5lb to 0.7lb)
Obese	30 or more	5kg to 9kg (11lb to 20lb)	0.2kg to 0.3kg (0.4lb to 0.6lb)

Will I be weighed while I'm pregnant?

Pregnant people tend to be weighed at each prenatal check in Canada. Among other things rapid weight gain could be a sign of gestational diabetes. Some midwives will not weigh you at every visit, but most will weigh you at the start and at the end of your pregnancy, at least. That's because your weight is a key detail if you have pain relief during labour.

What if I'm overweight?

If you had a high BMI before you conceived, you should try to limit the amount of weight you put on. Putting on lots more weight is not good for you or your baby. It may increase your risk of complications during your pregnancy and labour. These could include:

• preterm birth
• gestational diabetes
• having a big baby (SOGC nd)

Don't try to diet though. It could cause harm to you and to your unborn baby. Besides, it will not reduce your chances of getting high blood pressure. It's also unlikely to affect your risk of pre-eclampsia, which is related to blood pressure. It won't help your baby, either.

Instead, get some advice from your midwife, doctor, or a dietician about how to eat well. A healthy diet should ensure you don't pile on the pounds and it will keep you and your baby happy and thriving. Cut out snacks that are high in fat and sugar, such as cookies, doughnuts, candy and ice cream. Replace them with snacks such as fresh fruit, wholegrain crackers and low-fat cheese, a yogurt, or a handful of dried fruit.

Try to get out for a short walk every day. This counts as low-impact exercise, which is a great way for you to build up your fitness.

What if I'm underweight?

Speak to your midwife, doctor, or a dietician about how to eat over the coming months. Try to follow their advice. You may be more likely to have a premature or low-birth-weight baby (HC 2014) if your BMI is low. Babies who are born early and small sometimes need extra care when they are born.

What if I'm diabetic?

If you have diabetes, it's important to start your pregnancy with a healthy BMI. If you're reading this before you get pregnant, see your doctor to check out your diet. They'll also help you keep an eye on your blood sugar levels during your pregnancy (Feig et al 2018).

If you are already pregnant, you will need to do your best to keep your blood sugar levels stable. Ask your doctor for advice on the best diet to keep you and your baby healthy. If you have gestational diabetes, you will be cared for by an OB-GYN, or in shared care with a midwife and an OB-GYN. That’s because you’re thought of as a high-risk pregnancy. That means you and your baby will need extra care during the pregnancy to make sure it’s going OK.

Can I control my weight by eating right?

The best thing you can do is keep eating a balanced diet. If your pre-pregnancy weight was in the normal range, you will need about 340 extra calories a day while you are in your second trimester, and then 450 extra calories a day in your third trimester (SOGC nd).

These extra calories will help you gain the amount of weight your baby needs to grow. In fact, a healthy weight gain is the best way to tell whether you are getting the right amount of calories.

You are not eating for two. This amount of calories means only two or three added Canada Food Guide Servings from any food group each day (SOGC nd). This adds up to an extra snack or a small meal.

You should try to have a range of these foods:

• Bread, pasta, potatoes, rice and cereals (carbs). It's good to have wholegrain, such as brown rice and pasta, and wholewheat bread. Try to ensure that these starchy foods make up a third of what you eat daily.
• Fruit and veggies, at least five portions a day. These should make up a third of what you eat daily.
• Proteins, such as meat (but not liver), fish, eggs and legumes.
• Dairy products, such as milk, yogurt, and cheese. Lower fat versions can be a good option.

You don't need to have food or drink that is high in fat or sugar, such as cookies, doughnuts, or soft drinks. But it won't do you any harm to have them every so often, and in small amounts.

And don't forget it's not just about food! Exercise is good for you during pregnancy and can help you to stay a healthy weight (PHAC 2022). Read our pregnancy exercise guide for some tips on ways to keep fit.

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