Females of Reproductive Years
Pre-Pregnancy BMI
Gestational Weight Gain
Technical Notes
Gestational weight gain can be defined as the amount of weight gained between conception and just before the birth of the infant. In 2009, the Institute of Medicine (IOM) released guidelines that specify the amount of weight gain that is acceptable, based on the mother’s pre-pregnancy BMI. Staying within these guidelines during pregnancy will likely result in more healthy pregnancies and birth outcomes.
Women who gain an excessive amount of gestational weight according to the Gestational Weight Gain recommendations may be at higher risk of:
Additionally, infants born to mothers that gain more weight than recommended may be at increased risks of:
Infants born to women who gain less than their recommended gestational weight gain range may be at higher risk of:
Females of Reproductive Years
According to the CCHS in 2015-2016, less than half (42.9% (32.4%, 54.0%)) of Simcoe Muskoka females between the ages of 18 and 44 years were considered normal weight (BMI 18.5-24.9), approximately one quarter (22.7% (15.2%, 32.5%)) were overweight (BMI 25-29.9) and a third (32.1% (23.2%, 42.4%)) were obese (BMI >=30). A higher proportion of reproductive age females were obese in Simcoe Muskoka than in Ontario.
Pre-Pregnancy BMI
According to BORN, in 2018 less than half (46.6% (45.2%, 48.0%)) of new Simcoe Muskoka mothers began their pregnancies with a ‘normal’ BMI (BMI 18.5-24.9), significantly lower than the overall rate for Ontario (5.7% (50.4%, 51.0%)). One quarter of Simcoe Mothers (25.4% (24.1%, 26.6%)) had an overweight BMI (BMI 25.0-29.9) and approximately one quarter (23.9% (22.9%, 24.9%) had an obese BMI (BMI ≥ 30.0). Significantly more Simcoe Muskoka mothers began their pregnancies at an obese BMI compared to Ontario mothers (17.9% (17.8%, 18.1%)).
Gestational Weight Gain
Half (50.8% (49.3%, 52.3%)) of Simcoe Muskoka mothers gained more than the recommended amount of weight during their pregnancies. Three-in-ten (29% (27.6%, 30.3%) reported weight gain within the recommendations set out by the Institute of Medicine and a fifth (20.2% (19.0%, 21.5%) gained less than the recommended amount.
Those with overweight or obese pre-pregnancy BMI’s are more likely than those with underweight or normal BMI’s to gain more than the recommended amount of weight during pregnancy. The recommended gestational weight gain is less for the former group than the latter. A majority of women who began pregnancy as overweight (62.9% (59.9%, 65.7%)) or obese (69.4% (65.4%, 73.2%)) gained in excess of their recommended gestational weight gain range. Approximately forty percent (40.7% (38.5%, 42.9%)) of women who started their pregnancy with a normal BMI or who started their pregnancy underweight (35.3% (28.5%, 42.6%)) also gained an excess amount of weight during pregnancy.
For more information on having a healthy pregnancy, please visit the health unit's website on gestational weight gain.
Technical Notes
A high proportion of data (~20%) for BMI and weight gain is missing. Caution should be used when interpreting the results.
There are currently no evidence-based guidelines for gestational weight gain among women carrying three or more fetuses, women with a pre-pregnancy BMI ≥35.0, or underweight (BMI <18.5) women carrying twins. The results presented here are based on the exclusion of pregnancies that meet those criteria.
The CCHS BMI data for females of reproductive age are adjusted to correct for the overestimate of height and/or underestimate of weight inherent in self-reporting. This adjustment makes these data more comparable to measured height and weight.
The BORN BMI data for women who gave birth are based on measured height and weight.