Health Canada is revising its weight gain guidelines for pregnant women to include a suggested rate of weight gain as well as recommendations for total weight gain.

The new guidelines also include a specific recommendation for weight gain for obese women.

The recommendations are based on a women's body mass index (BMI) prior to pregnancy. Those BMI rangess are now aligned with the World Health Organization's definitions of underweight (BMI less than 18.5), normal weight (BMI of 18.5 to 24.9), overweight (BMI of 25.0 to 29.9) and obese (BMI of 30 or greater)

The new guidelines state that women with:

  • BMI less than 18.5 should aim to gain between 28 and 40 pounds (12.5 and 18 kilograms).
  • BMI between 18.5 and 24.9 should aim to gain between 25 and 35 lbs (11.5 to 16 kg)
  • BMI between 25 and 29.9 should aim to gain between 15 and 25 lbs (7 to 11.5 kg)
  • BMI of greater than 30 should gain no more than 11 to 20 lbs (five to nine kg)

As well, the recommended mean rate of weight gain in the second and third trimester are:

  • BMI less than 18.5 prior to pregnancy should aim to gain 0.5 pounds a week (1.0 kilograms)
  • BMI between 18.5 and 24.9 should aim to gain 0.4 lbs a week (1 kg)
  • BMI between 25 and 29.9 should aim to gain 0.3 lbs a week (0.6 kg)
  • BMI of greater than 30 should gain no more than 0.2 lbs per week (0.5 kg)

All of the guidelines are for women carrying a single baby.

Health Canada adjusted the recommendations to conform to the latest recommendations from the U.S. Institute of Medicine, after consultation with an external group of expert advisors.

The IOM devised its recommendations after analyzing the latest data from observational studies, which consistently showed that women who gain within the recommended ranges experience better pregnancy outcomes.

Research shows that many Canadian women gain more than Health Canada's recommended weight gain during pregnancy. The agency says it's important for women to maintain a healthy weight gain during pregnancy to minimize risks to the mother and baby.

Excess weight gain increases the risk of Caesarean sections or retaining extra weight after delivery, which can lead to obesity. For the child, the risks include being born pre-term or larger than normal.

Gaining too little weight during pregnancy can also negatively affect fetal growth and increase the risk of pre-term delivery.

Health Canada is developing a quick reference tool and weight gain tracker for health professionals to support the revised guidelines. And an interactive web-based tool that will assist women in tracking their weight gain during pregnancy is also being developed. Those materials should be available next spring.