Pregnancy Weight

Gaining the right amount for you and your baby


When you’re pregnant, you need more nourishment than usual.

The average weight gain during pregnancy is 11.5 to 16 kilograms (25 to 35 pounds), most of it during the second and third trimesters. About a third (35 per cent) of that extra weight is your baby and your placenta and amniotic fluid. The rest of it is from increased blood and fluids and tissue in the breasts and uterus.

Weight gain according to BMI

How much you need to eat and how much weight you need to gain depends on your pre-pregnancy body mass index (BMI), a calculation
based on your height and weight.

  • Underweight — BMI less than 18.5. Gain between 12.5 and 18 kg (28 and 40 lbs.)
  • Normal weight — BMI 18.5 and 24.9. Gain between 11.5 to 16 kg (25 and 35 lbs.)
  • Overweight — BMI 25 to 29.9. Gain between 7 and 11 kg (15 and 25 lbs.)
  • Obese — BMI 30 or more. Gain between 5 and 9 kg (11 and 20 lbs.)

Source: AHS Healthy Pregnancy Weight Gain

About half of Canadian women gain too much weight during pregnancy, which can make them uncomfortable, make labour more complicated and make it harder to lose weight after having their baby.

Extra weight during pregnancy can also increase the risk of developing high blood sugar leading to gestational diabetes. It can also increase the risk of hypertension and cardiovascular disease later in life. Too much weight gain can also cause your baby to be overweight or obese in childhood.

Not gaining enough weight during pregnancy also has risks. Babies of underweight mothers are more likely to be born preterm or with low birthweight (less than 2.5 kg or 5 lbs. 8 oz.). This can put them at greater risk of disease in the first few weeks of life and physical and developmental disabilities and health problems later in life.

When and how much more to eat:

  • First trimester — no extra calories
  • Second trimester — you need about 350 more calories a day
  • Third trimester — you need about 450 more calories a day
  • While breastfeeding — 350 to 400 more calories a day
  • When pregnant, eating every two to four hours gives your baby a steady supply of nutrients and may help you feel better if you’re nauseated.

This story appeared in the Spring 2017 edition of Health Matters, the quarterly magazine produced by Calgary’s seven primary care networks.