Healthy Weight Gain in Pregnancy: What the Guidelines Say

How much weight should you gain in pregnancy? See Health Canada's ranges by pre-pregnancy BMI, what to expect each trimester and why dieting is not recommended.

Gaining weight is a normal, healthy part of pregnancy. It supports your baby's growth, the placenta, extra blood and fluid, and the energy stores you will draw on while breastfeeding. Guidelines offer a range rather than a single number, based on your weight before pregnancy.

See your personal range and a week-by-week guide with our free pregnancy weight gain calculator.

Where does the weight go?

Only part of the weight gained in pregnancy is the baby. The rest includes the placenta, amniotic fluid, a larger uterus, breast tissue, increased blood volume, extra fluid in your tissues and some fat stores. Knowing this can make the numbers on the scale feel less mysterious.

Recommended total gain by pre-pregnancy BMI

Health Canada uses the 2009 Institute of Medicine guidelines for a single baby. The recommended total gain depends on your body mass index (BMI) before pregnancy:

• BMI under 18.5: 12.5 to 18 kg (28 to 40 lb)
• BMI 18.5 to 24.9: 11.5 to 16 kg (25 to 35 lb)
• BMI 25.0 to 29.9: 7 to 11.5 kg (15 to 25 lb)
• BMI 30.0 or higher: 5 to 9 kg (11 to 20 lb)

For people with a BMI of 35 or higher, a care provider may suggest a lower gain based on individual circumstances.

Pattern of gain across the trimesters

Weight gain is usually slow at first and steadier later on:

• First trimester: a small gain, typically about 0.5 to 2 kg (1 to 4 lb) in total. Some people lose a little weight because of nausea, which is common.
• Second and third trimesters: a steadier weekly gain. As a guide, Health Canada suggests about 0.5 kg per week if you started underweight, 0.4 kg for a BMI of 18.5 to 24.9, 0.3 kg for a BMI of 25 to 29.9 and 0.2 kg for a BMI of 30 or more.

Week-to-week changes are normal. Your care provider will look at your overall trend over time, not any single weigh-in.

Twins and multiples

Recommendations are higher if you are carrying twins. Provisional guidelines suggest 17 to 25 kg for a BMI of 18.5 to 24.9, 14 to 23 kg for a BMI of 25 to 29.9 and 11 to 19 kg for a BMI of 30 or more. There is not enough evidence to set a range for people with a pre-pregnancy BMI under 18.5 carrying twins, or for triplets and more. Your care team will guide you.

Eating for one, plus a little

The old idea of "eating for two" is misleading. In the first trimester, most people do not need extra calories. Later on, needs rise modestly: about 340 to 350 extra calories a day in the second trimester and about 450 extra calories a day in the third. That is roughly two to three extra Canada's Food Guide servings, such as a yogurt and a piece of fruit, or a small sandwich.

A few other basics help:

• take a daily prenatal multivitamin with folic acid, as recommended by Health Canada
• choose a variety of vegetables, fruit, whole grains and protein foods
• stay active with activities that feel comfortable, if your provider agrees
• follow food safety advice, such as avoiding unpasteurised products and limiting certain fish

No dieting during pregnancy

Pregnancy is not the time to try to lose weight, even if you started at a higher weight. Restricting food can mean your baby does not get the energy and nutrients needed for growth. If you are gaining above or below your range, the goal is usually to adjust food choices and activity with support, not to diet.

Gaining well above the range is linked with a higher chance of gestational diabetes, high blood pressure and a larger baby. Gaining well below it is linked with a higher chance of a small baby or preterm birth. Your provider can help you find a pattern that fits you.

When to get medical advice

Talk to your doctor, midwife or obstetrician if:

• you are losing weight after the first trimester, or cannot keep food or fluids down
• you lose more than 5 percent of your pre-pregnancy weight in early pregnancy
• your weight is consistently well above or below your recommended range
• you are worried about your eating, or have a history of disordered eating

Seek care urgently if you have a sudden weight gain over a few days, especially with swelling of your face or hands, a severe headache, vision changes or upper abdominal pain. These can be signs of preeclampsia. For severe vomiting with signs of dehydration, such as very dark urine or dizziness, get care the same day. In BC, call 8-1-1 for nurse advice, or 9-1-1 in an emergency.