Weight gain during pregnancy

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.

Weight gain by trimester

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-related complications in pregnancy

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.

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.

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.

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

Photo: iStock.com/AtnoYdur