With the majority of Canadian adults having overweight or obesity (by Body Mass Index (BMI) criteria), it does not come as a surprise that many reproductive-aged women with elevated body weight are actively trying to lose weight.  Women who I meet as patients often express confusion about whether they should still be trying to lose weight if/when pregnant – when they search it up on google, they get all kinds of advice.


So: Is it appropriate to try losing weight in pregnancy?


The answer to this is no.  As blogged previously, weight gain is recommended in pregnancy, but the amount of weight gain advised varies by body mass index (BMI) (you can calculate your BMI here).


The 2020 Canadian Obesity Guidelines advise the target weight gain in pregnancy as follows (for a singleton pregnancy):

  • BMI <18.5 kg/m2 (‘underweight’):        28-40lb (12.5-18kg)
  • BMI 18.5-24.9 (‘normal’ or ‘healthy’):   25-35lb (11.5-16kg)
  • BMI 25-29.9 (‘overweight’):                    15-25lb  (7-11.5kg)
  • BMI >30 (‘obesity’):                                  11-20lb  (5-9kg)


This guidance was developed based on observational studies, which consistently show that gestational weight gain above or below these recommended ranges is associated with adverse outcomes for mom and baby. About 19lbs (8.5kg) are gained in pregnancy from the weight of the full term baby, placenta, amniotic fluid, uterine muscle, increase in mom’s blood volume and increase in total body water – in other words, excluding any increase in mom’s fat tissue. Thus, for women with obesity before pregnancy (and many without), staying within the above targets for weight gain can be a challenge.


To reduce the risk of adverse outcomes in the current or future pregnancy, the three main goals for women with obesity are:

  • To enter pregnancy at a lower body mass index (BMI)
  • Targeting weight gain during pregnancy to 11-20lb (5-9kg)
  • Returning to at least your pre-pregnancy BMI in the year after delivery.


The Canadian Obesity guidelines provide recommendations on how to support women in achieving these goals (see my prior blog here, and the guidelines chapter here).


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