Weight gain during pregnancy

Weight gain during pregnancy
How much weight should you gain during pregnancy? It all depends on your pre-pregnancy weight.

Gaining weight is a normal part of pregnancy and essential for your baby’s healthy development. However, weight gain recommendations are specific to each mother and vary according to trimester.

How much weight should you gain during pregnancy?

The amount of weight you should gain depends on your pre-pregnancy weight. Women starting out at a healthy weight should gain 11–16 kg (25–35 lb.) during their pregnancy. That said, women carrying twins or multiples should gain more.

Women who are underweight need to put on about 12.5–18 kg (28–40 lb.). Conversely, those who are overweight may be advised to gain no more than 11.5 kg (25 lb.). Keep in mind that these numbers are not requirements for a successful pregnancy and delivery. A healthy diet, regular exercise, and good sleeping habits are at least as important as weight gain.

Weight-loss diets are not recommended during your pregnancy, as they may interfere with your energy and nutritional intake. They can also jeopardize your baby’s development and increase your fatigue.

But that doesn’t mean you should completely let go and put on more weight than necessary. Gaining too much can negatively affect your pregnancy and make it harder to get back to a healthy weight after delivery.

What is a healthy weight?
Your body mass index (BMI) is often used to determine whether you’re at a healthy weight. However, this index is not reliable for teenagers or very muscular athletes. Furthermore, it should not be used to assess healthy weight during pregnancy. It’s best to speak with your doctor or a nutritionist to determine your weight category.

Weight gain by trimester

Much of the weight gained during pregnancy is related to all the physiological changes that occur to accommodate the baby.

Weight gain can change from one trimester to the next. Generally, women gain less weight in the first trimester, about 500 g–2kg (1–4.5 lb.).

Some expectant mothers even lose weight in early pregnancy due to a loss of appetite caused by morning sickness. Usually, they’re able to regain the pounds they lost and reach their recommended weight once the nausea subsides.

In the second and third trimesters, weight gain varies from person to person. Broadly speaking, you can expect to put on about 225 g–1 kg (0.5–1 lb.) per week during this period.

While you can monitor your weight gain week by week, the important thing is to maintain a balanced diet. If you eat well and stay active during pregnancy, you’ll gain a healthy amount of weight for you and your baby.

Weight gain distribution

Here’s a sample breakdown of weight distribution for a woman who gains 12.5 kg (about 28 lb.) during a 40-week pregnancy.

  • The increased blood volume, placenta, uterus, and amniotic fluid account for 5 kg (11 lb.)
  • The fetus accounts for 3.5 kg (8 lb.)
  • The accumulated fat, which serves as an important energy reserve for the mother and fetus throughout the pregnancy, accounts for 3.5 kg (8 lb.)
  • The mother’s increased breast size accounts for 0.5 kg (1 lb.)
Weight gained in early pregnancy
Until your 15th week of pregnancy, any pounds you put on are essentially stores of protein (in your muscles) and fat (in your adipose tissue). These reserves will play an important role later in your pregnancy. Your baby will begin to grow exponentially in the second trimester.

Weight-related complications in pregnancy

To prevent weight-related complications, it’s best to reach or get closer to a healthy weight before becoming pregnant.

Weight gain during pregnancy should be sufficient but not excessive to ensure the health of the mother and baby. Women who don’t gain enough weight are at greater risk of having a low birth weight baby. Low birth weight babies are more likely to have a physical or mental disability and are at higher risk of getting sick.

However, gaining too much can be problematic as well. Excessive weight gain during pregnancy increases your risk of developing gestational diabetes and hypertension, giving birth by C-section, and staying overweight after delivery.

Disordered eating in pregnancy
A woman’s body changes drastically during her nine months of pregnancy. Some expectant mothers become fixated on their weight gain and may try to control it through obsessive dieting. This eating disorder is commonly known as pregorexia. Women who suffer from pregorexia need a supportive doctor and psychologist to help them have a healthy pregnancy.

Returning to your pre-pregnancy weight

About 70 percent of pregnant women worry that they won’t return to their pre-pregnancy weight after delivery. Fortunately, in most cases, you just have to be patient.

Women who gain too much weight during their pregnancy tend to have a harder time shedding the extra pounds.

A year after giving birth, about one in two women have returned to their pre-pregnancy weight, whereas about one in four women continue to carry an extra 4.5 kg (10 lb.) or more. Breastfeeding mothers generally find it easier to return to their pre-pregnancy weight.

The best way to get back to a healthy weight is to eat well and follow your hunger and fullness cues. Weight-loss diets are not recommended immediately after childbirth, as they put unnecessary strain on the new mother. If you’ve just had a baby, you need calories to recover and, if you’re breastfeeding, produce milk.

For tips on healthy eating, consult Canada’s food guide. A nutritionist can also be a valuable asset as you work toward a healthy weight.

Things to keep in mind

  • Gaining too little or too much weight increases the risk of complications during pregnancy and childbirth.
  • Good eating habits and regular exercise are important for a healthy pregnancy, regardless of weight.
  • Weight-loss diets are not recommended during and immediately after pregnancy. For tips on healthy eating, speak with a nutritionist.


Naître et grandir

Scientific review: Stéphanie Côté, M.Sc., nutritionist
Research and copywriting: The Naître et grandir team
Updated: October 2019


Photo: iStock.com/AtnoYdur


Sources and references

Note: The links to other websites are not updated regularly, and some URLs may have changed since publication. If a link is no longer valid, please use search engines to find the relevant information.

  • Côté, Stéphanie. Grossesse : 21 jours de menus. Montreal, Éditions Modus Vivendi, “Savoir quoi manger” series, 2018, 226 pp.
  • Doré, Nicole and Danielle Le Hénaff. From Tiny Tot to Toddler: A practical guide for parents from pregnancy to age two. Quebec City, Institut national de santé publique du Québec. www.inspq.qc.ca
  • Ladewig, Patricia W., et al. Soins infirmiers en périnatalité. 4th ed., Saint-Laurent, ERPI, 2010, 1,101 pp.