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of public health epidemiology in Ontario

Gestational Weight Gain Core Indicator

  • Proportion of women with gestational weight gain (GWG) within, greater than, or less than recommended.

Method of Calculation

Proportion of Pregnant Women who Gained Weight within GWG Recommendations
Number of pregnant women who gained weight within GWG recommendations*
Total number of pregnant women
*GWG recommendations depend on both pre-pregnancy BMI and number of fetuses, see Tables 1 and 2 in Indicator Comments.
Proportion of Pregnant Women who Gained Weight less than GWG Recommendations
Number of pregnant women who gained less weight than GWG recommendations*
Total number of pregnant women
*GWG recommendations depend on both pre-pregnancy BMI and number of fetuses, see Tables 1 and 2 in Indicator Comments
Proportion of Pregnant Women who Gained Weight more than GWG Recommendations
Number of pregnant women who gained more weight than GWG recommendations*
Total number of pregnant women
*GWG recommendations depend on both pre-pregnancy BMI and number of fetuses, see Tables 1 and 2 in Indicator Comments

Recommended Subset Analysis Categories

Geographic Areas of Maternal Residence
  • Ontario
  • Public Health Unit

Data Sources

Numerator & Denominator Alternative Data Sources

Original Source:

Better Outcomes Registry Network (BORN) Ontario

Distributed by:

Better Outcomes Registry Network (BORN) Ontario

Suggested Citation:

BORN Information System [years], Date Extracted: [date].


Data Elements in the BORN Information System (BIS)

Name and Description




Pre-pregnancy maternal weight 
The mother's self-reported weight closest to conception and no later than 12 weeks of gestation (metric or imperial units with conversion done by BORN Ontario).
  • Numeric [kg]
  • Labour
  • Birth (Mother)
  • Antenatal General
  • Antenatal Specialty


Maternal Height 
Maternal height, measured in imperial or metric units.  Reported in metric units.
  • Numeric [cm]
  • Labour
  • Birth (Mother)
  • Antenatal General
  • Antenatal Specialty


Maternal BMI (calculated) 
Maternal pre-pregnancy Body Mass Index (BMI) defined as weight in kilograms divided by the square of the height in metres (kg/m2).
  • Numeric [kg/m2]
  • Labour
  • Birth (Mother)
  • Antenatal General
  • Antenatal Specialty


Maternal Weight at the End of Pregnancy 
Maternal self-reported weight closest to the end of pregnancy.
  • Numeric [kg]
  • Birth (Mother)


Number of Fetuses 
Number of fetuses.
  • 1-8
  • Unknown
  • All Encounters


Maternal Weight Gain in Pregnancy (calculated) 
Calculated field of weight gain in pregnancy.
  • Numeric [kg]
  • Labour
  • Birth (Mother)


QUESTION FOR THE SUBGROUP: Should this second table be listed under "Recommended Subset Analysis Categories" instead of here???
(Also, the Weight Gain Recommended Group category may even just below in the Method of Calculation, but this is something we need to discuss with the CIWG to have some sort of idea of when something is a subset analysis vs when is it a version of an indicator...)



Maternal Weight Gain Recommended Group                           
  • Below
  • Within
  • Above 
  • Missing Data
Number of Fetuses
  • Singleton
  • Twins
  • Triplets
  • Quadruplets
  • Quintuplets
  • Sextuplets
  • Missing Data
Maternal BMI Group 01 Lev 1
  • Underweight (<18.5)
  • Normal (18.5 - 24.9)
  • Overweight (25.0 - 25.9)
  • Obese Class I (30.0 - 34.9)
  • Obese Class II (35.0 - 39.9)
  • Obese Class III (>40.0)
  • Missing Data
Newborn DOB Calendar Year
  • 2012 - Present

Analysis Checklist  

Maternal Inclusion and Exclusion
  • As part of the GWG calculation, the following groups should be excluded from both numerator and denominator (recommended filters are specified in the instructions below): all pregnancies with a maternal pre-pregnancy BMI >34.9, and pregnancies with three or more fetuses. As per 2009 guidelines from the Institute of Medicine (IOM)1 and the Society of Obstetricians and Gynaecologists (SOGC)2, there is insufficient information to develop guidelines for these groups. However, these exclusions have not been made in the "Maternal Weight Gain Recommended” dimension that has been calculated in the Public Health Cube and must be made through the analysis.
  • Maternal Recommended Weight Gain is not calculated for multiple birth pregnancies among mothers with pre-pregnancy BMI <18.5. These have been coded in the Public Health Cube as missing. Ideally these would be excluded; however, it is not possible to do this type of double-barreled filter in the cube. The number of these pregnancies would be small.
  • Niday Perinatal Data (i.e., data prior to April 1, 2012) is available from BORN upon request however, the gestational weight gain variable was not part of Niday and did not became part of the BIS until April 2012.

If Using the Public Health Standard Reports
  • Currently the GWG indicator is not in Public Health Reports. A request has been made to BORN Ontario to add this indicator.

If using the Public Health Cube
  • Please follow the general analysis checklist for the BORN Information System data source.  
  • Select Dimension: "Maternal Weight Gain Recommended Group” (found under Dimensions > Pregnancy > Maternal Characteristics)
  • Select Measure: "# of Pregnancies – Women Who Gave Birth” (found under Measures > Pregnancy)
  • Specify Filters by right clicking on each of the following dimensions and selecting the following categories:
    • "Num of Fetuses” (found under Pregnancy > Pregnancy History) = "Singleton” AND "Twins” AND "Missing data”.
    • "Maternal BMI Group 01 Lev 1” (found under Pregnancy > Maternal Characteristics) = Underweight (<18.5) AND Normal (18.5 – 24.9) AND Overweight (25.0-25.9) AND Obese class I (30.0-34.9) AND Missing data.
    • Newborn DOB Calendar Year (found under Newborn DOB > Newborn DOB Calendar) = Deselect 2012 (and others as appropriate to your analysis).
  • Calculate percentages within the Cube or export to Excel.

Indicator Comments

Gestational Weight Gain Guidelines and Recommendations
  • The Public Health Cube documentation indicates that the BIS uses the 2011 SOGC guidelines2 for singleton pregnancies to calculate recommended weight gain for non-obese pre-pregnancy BMIs and 2009 IOM guidelines1 for all other pregnancies (obese and multiple gestation). However, since the SOGC and IOM guidelines are the same for singleton non-obese pregnancies, the BIS essentially uses the IOM guidelines for all categories of gestational weight gain. BORN generally prefers to indicate the Canadian standards to which they are aligned first and foremost, which would be the SOGC guidelines. 
  • The IOM updated their GWG guidelines in 2009 to consider the health of both infants and mothers, the trends towards increasing twin and triplet pregnancies, and the higher rates of obesity in the population. The increasing percentage of women who are entering pregnancy overweight or obese and who are gaining too much weight during pregnancy increases the risk of chronic disease and puts the mother and baby’s health at risk. As a result, prepregnancy Body Mass Index and twin pregnancies were incorporated into the updated guidelines. There are no recommendations for triplet and other higher order pregnancies1.
  • Health Canada3, the Public Health Agency of Canada4, and Eat Right Ontario5 have adopted the 2009 IOM recommendations. See Table 1 and Table 2 for specific GWG recommendations.

    Table 1: Health Canada / IOM gestational weight gain (GWG) recommendations for singleton pregnancies1,3.
        Mean rate of weight gain in the
    2nd and 3rd trimester 
    Recommended range of
    total weight gain*  
    Pre-pregnancy BMI category  kg  lbs  kg  lbs
     BMI < 18.5: Underweight 0.5 1.0 12.5 - 18.0 28 - 40
     BMI 18.5 - 24.9: Normal Weight 0.4 1.0 11.5 - 16.0 25 - 35
     BMI 25.0 - 29.9: Overweight 0.3 0.6 7.0 - 11.5 15 - 25
     BMI >= 30: Obese** 0.2 0.5 5.0 - 9.0 11 - 20

    * Calculations assume a total of 0.5-2.0 kg (1.2-4.4 lbs) weight gain in the first trimester
    ** Health Canada advises that the obesity category is for those with a BMI 30.0-34.9. There is no evidence to suggest an appropriate weight gain range if maternal BMI is 35.0 or greater, in which case specific weight gain advice from a health care provider is required.

    Table 2: Health Canada / IOM gestational weight gain (GWG) recommendations for twin pregnancies1,3.
        Recommended range of
    total weight gain*  
    Pre-pregnancy BMI category  kg  lbs
     BMI < 18.5: Underweight * *
     BMI 18.5 - 24.9: Normal Weight 17 - 25 37 - 54
     BMI 25.0 - 29.9: Overweight 14 - 23 31 - 50
     BMI >= 30: Obese** 11 - 19 25 - 42

    * Based on an IOM review of evidence, there is insufficient information available to develop guidelines for underweight women carrying twins.
    ** Health Canada advises that the obesity category is for those with a BMI 30.0-34.9. There is no evidence to suggest an appropriate weight gain range if maternal BMI is 35.0 or greater, in which case specific weight gain advice from a health care provider is required.
  • GWG recommendations from the SOGC2 are slightly different from the 2009 IOM1 and Health Canada3 guidelines. The SOGC guidelines differ when maternal BMI is more than 30 (at least 7 kg versus a range of 5.0-9.0 kg) and for twin pregnancies where the SOGC recommendation is a weight gain of 16.0-20.5 kg with no breakdown by pre-pregnancy BMI.
  • While it generally is not recommended to use adult BMI cut-offs for those under 18, the IOM (2009) recommends use of adult BMI for those under 18 years of age for GWG recommendations. A higher percentage of younger adolescents will likely be categorized in the underweight BMI category and will therefore be advised to gain more weight during pregnancy1.
  • The recommended weight gain ranges for short women and for racial or ethnic groups are the same as those for the whole population1.

Effects of Gestational Weight Gain
  • Exceeding GWG recommendations is associated with increased risk of caesarean section7, increased risk of maternal postpartum weight retention up to three years post index pregnancy7,8,9, increased risk of large-for-gestational age babies7, and increased risk of children being overweight or obese later in life10,11,12.
  • Gaining insufficient weight during pregnancy and not meeting the GWG recommendation is associated with preterm birth and increased risk of small-for-gestational age babies7.
  • Various factors may affect GWG including pre-pregnancy weight, age, parity, education, and income13.
  • The 2008 Canadian Perinatal Health Report listed shoulder dystocia, brachial plexus injury, and Erb’s palsy as possible adverse outcomes for infants being born large-for-gestational age (LGA) along with increased risk of postpartum hemorrhage as a maternal complication14. Those babies born with a high birth weight may be at increased risk of type 2 diabetes mellitus later in life14. Other reported outcomes include increased risk of caesarean delivery, maternal death and fistulae1. More recent publications list the following as adverse health outcomes associated with LGA: perinatal tear, post-partum hemorrhage, shoulder dystocia, hypoglycemia15, hypertension16, and overweight/obesity17,18.
  • Reported adverse birth outcomes associated with small-for-gestational age (SGA) babies include higher risks of infant mortality, cerebral palsy, hypoglycemia, hypocalcemia, polycythemia and birth asphyxia. Longer term outcomes include increased risk of central adiposity, insulin resistance, metabolic syndrome, type 2 diabetes, hypertension, and coronary heart disease. Being born small plus a rapid weight gain in the first year of life increases the risk of these outcomes1

Measurement Limitations
  • Various limitations exist in determining height, weight, and gestational weight gain. A Canadian study found that females tend to over-report their height by 0.5 cm on average and under-report their weight by an average of 2.5 kg. When based on measured rather than on self-reported values, the prevalence of obesity was 6 points higher among females compared to males19.
  • Misreporting of weight and height leads to measurement error in the BMI calculation, which then leads to misclassification into BMI categories and gestational weight gain categories. One study found that associations between self-reported pre-pregnancy BMI and adverse birth outcomes may be slightly overestimated due to misclassification; however, the conclusion that complications increased with higher BMI remained20. Misreporting of weight varies by BMI category and ethnicity21. Pregnant women are more likely to underreport their weight compared to non-pregnant women22.
  • It has been reported that despite the limitations of self-reported weight and height, there likely will be no difference in whether women are categorized as being below, within, or above their gestational weight gain range23,24, suggesting that self-reported height and weight measures are sufficiently valid for this use.
  • Using measures of gestational weight gain and not controlling for gestational age at delivery may obscure the true contribution of gestational weight gain to maternal and perinatal health outcomes25. A recent re-analysis of the Maternity Experiences Survey examining the association between pre-pregnancy BMI, GWG and caesarian sections excluded preterm births (<37 weeks gestation)26.
  • However, analysis by the Reproductive Health Sub-Group found there was no difference in GWG for preterm versus full-term pregnancies. As a result, it is not necessary to report GWG rates separately for these populations unless it is of specific interest in your analyses.
  • It is currently unknown whether the current Health Canada GWG guidelines apply to pregnant women with pre-existing diabetes or for women with gestational diabetes. Best available evidence suggests that women with diabetes who exceed their GWG guideline experience similar adverse pregnancy and birth outcomes as their non-diabetic counterparts27-31. Therefore, there is not enough evidence to justify the exclusion of this group from analysis at this time.
  • Analysis by the Reproductive Health Sub-Group found there was no difference in GWG rates for women with diabetes versus women without diabetes. As a result, it is not necessary to report GWG rates separately for these populations unless it is of specific interest in your analyses.
  • Height and weight in the BIS are collected from the Ontario Antenatal Record (OAR) form that is sent by a woman’s health care provider to the hospital where they intend to give birth. In situations where the form is not present at the hospital when and where the woman gives birth, height and weight will be unknown.
  • There is a relatively high degree of missing data for the GWG indicator, but it does vary by hospital and therefore by PHU. The total missing for Ontario in the first 3 years of available BIS data shows a decrease in the proportion of records with missing values (40% in 2012; 35% in 2013 and 26% in 2014). Overall, the total missing varied across health units, ranging for 6% to 48%32. It’s important to understand the missing data in this indicator for your health unit prior to reporting on it.


Cited References
  1. IOM (Institute of Medicine) and NRC (National Research Council). 2009. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: The National Academies Press. Available at:
  2. Society of Obstetricians and Gynaecologists. Clinical practice guideline: Obesity in pregnancy. J Obstet Gynaecol Can. 2010 Feb;32(2):165-73. Available from:
  3. Health Canada. Prenatal Nutrition Guidelines for Health Professionals: Gestational Weight Gain. Available at:
  4. Public Health Agency of Canada. The Healthy Pregnancy Guide. Available at:
  5. Eat Right Ontario. Planning to Be Pregnant? Healthy Tips for Healthy Weight Gain. Available at:
  6. Ontario Public Health Association. Shift - Enhancing the health of Ontarians: A call to action for preconception health promotion and care. 2014. Toronto, ON. Available at:
  7. Viswanathan M, Siega-Riz AM, Moos M-K, Deierlein A, Mumford S, Knaack J, Thieda P, Lux LJ, Lohr KN. Outcomes of Maternal Weight Gain, Evidence Report/Technology Assessment No. 168. (Prepared by RTI International–University of North Carolina Evidence-based Practice Center under Contract No. 290-02-0016.) AHRQ Publication No. 08-E009. Rockville, MD: Agency for Healthcare Research and Quality. May 2008. Available at:
  8. Nehring I, Schmoll S, Beyerlein A, Hauner H, von Kries R.  Gestational weight gain and long-term post-partum weight retention: a meta-analysis. Am J Clin Nutr. 2011 Nov; 94(5):1225-31. Available at:
  9. Mannan M, Doi SA, Mamun AA. Association between weight gain during pregnancy and postpartum weight retention and obesity: a bias-adjusted analysis. Nutr Rev. 2013 Jun; 71(6):343-52.
  10. Nehring I, Lehmann S, von Kries R. Gestational weight gain in accordance to the IOM/NRC criteria and the risk for childhood overweight: a meta-analysis. Pediatr Obes. 2013 Jun; 8(3): 218-24.
  11. Mamun AA, Mannan M, Doi SAR. Gestational weight gain in relation to offspring obesity over the life course: a systematic review and bias-adjusted analysis. Obes Rev. 2014 Apr; 15(4):338-47.
  12. Tie HT, Xia YY, Zeng YS, Zhang Y, Dai CL, Guo JJ, Zhao Y. Risk of childhood overweight or obesity associated with excessive weight gain during pregnancy: a meta-analysis. Arch Gynecol Obstet. 2014 Feb; 28 9(2):247-57.
  13. Public Health Agency of Canada. What Mothers Say: The Canadian Maternity Experiences Survey. Ottawa, 2009. Available at:
  14. Public Health Agency of Canada. Canadian Perinatal Health Report, 2008 Edition. Ottawa, 2008. Available at:
  15. Weissmann-Brenner A, Simchen MJ, Zilberberg E, Kalter A, Weisz B, Achiron R, Dulitzky M. Maternal and neonatal outcomes of large for gestational age pregnancies. Acta Obstet Gynecol Scand. 2012 91:844–849.
  16. Schellong K, Schulz S, Harder T, Plagemann A. Birth weight and long-term overweight risk: systematic review and a meta-analysis including 643,902 persons from 66 studies and 26 countries. PLoS One. 2012, 7(10): e47776. Available at: 776.
  17. Yu ZB, Han SP, Zhu Z, Zhu C, Wang XJ, Cao XG, Guo XR. Birth weight and subsequent risk of obesity: a systematic review and meta-analysis. Obes Rev. 2011 Jul; 12(7):525-542.
  18. Mu M, Want SF, Sheng J, Zhao Y, Li HZ, Hu CL, Tao FB. Birth weight and subsequent blood pressure: a meta-analysis. Arch Cardiovasc Dis. 2012 Feb: 105(2):99-113. Available at:
  19. Sheilds M, Connor Gorber S, Tremblay M. Estimates of obesity based on self-report versus direct measures. Health Reports, May 2008, 82-003x vol. 19, no.2. Available at: 
  1. Bodnar LM, Siega-Riz AM, Simham HN, Diesel JC, Abrams B. The impact of exposure misclassification on associations between pre-pregnancy body mass index and adverse pregnancy outcomes. Obesity (Silver Spring). 2010. Nov; 18(11):2184-2190. Available at:
  2. McKoy JN, Hartmann KE, Jerome RN, Andrews JC, Penson DF. Future Research Needs for Outcomes of Weight Gain in Pregnancy. Future Research Needs Paper No. 6. AHRQ Public ation No. 11-EHC004-EF. Rockville, MD: Agency for Healthcare Research and Quality. November 2010. Available at:
  3. Craig BM, Adams AK. Accuracy of body mass index categories based on self-reported height and weight among women in the United States. Matern Child Health J. 2009 Jul;13(4):489-496.
  4. Shin D, Chung H, Weatherspoon L, Song WO. Validity of pre-pregnancy weight status estimated from self-reported height and weight. Maternal and Child Health Journal, December 2013.
  5. Holland E, Moore Simas TA, Doyle DK, Liao X, Waring ME. Self-reported pre-pregnancy weight versus weight measured at first prenatal visit: Effects on categorization of pre-pregnancy body mass index. Matern Child Health J. 2013 Dec; 17(10):1872-1878. Available at:
  6. Hutcheon JA, Bodnar LM, Joseph KS, Abrams B, Simham N, Platt RW. The bias in current measures of gestational weight gain. Paediatr Perinat Epidemiol. 2012 Mar;26(2):109-116. Available at:
  7. Dzakpasu S, Fahey J, Kirby RS, Tough SC, Chalmers B, Heaman MI, Bartholomew S, Biringer A, Darling EK, Lee LS, McDonald S. Contribution of pre-pregnancy body mass index and gestational weight gain to caesarean births in Canada. BMC Pregnancy and Childbirth. 2014 18(14):106. Available at:
  8. Cheng YW, Chung JH, Kurbisch-Block I, Intrurrisi M, Shafer S, Caughey AB. Gestational weight gain and gestational diabetes mellitus. Obstet Gynecol. 2008 Nov;112(5):1015-1022. Available at:
  9. Harper LM, Shanks AL, Adibo AO, Colvin R, Macones GA, Cahill AG. Gestational weight gain in insulin resistant pregnancies. J Perinatol. 2013 Dec; (33)12:929-33. Available at:
  10. Berggren EK, Steube AM, Boggess KA. Excess maternal weight gain and large for gestational age risk among women with gestational diabetes. Am J Perinatol. 2014 June 27. Available at:
  11. Harper LM, Tita A, Biggio JR. The institute of medicine guideline for gestational weight gain after a diagnosis of gestational diabetes and pregnancy outcomes. Am J Perinatol. 2014, June 27. [e-pub ahead of print].
  12. Egan AM, Dennedy MC, Al-Ramli W, Heerey A, Avalos G, Dunne F. ATLANTIC-DIP: Excessive Gestational Weight Gain and Pregnancy Outcomes in Women with Gestational or Pre-gestational Diabetes Mellitus. J Clin Endocrinol Metab. 2014 Jan;99(1):212-219.
  13. BORN Information System 2012-2015, Special request from Public Health Cube, Date Extracted: September 22, 2015. 


Lead Authors

Becky Blair

Jessica Deming

Mary-Anne Pietrusiak

Amira Ali

Arianne Folkema

Erin Graves


Andrew Lam, Region of Peel

Jackie Muresan, Region of Peel

Contributing Authors

Reproductive Health Sub-Group

Other Acknowledgements

We are very grateful for the support offered by Sharon Bartholomew, Senior Epidemiologist, Public Health Agency of Canada, for her advice and support related to the Maternity Experiences Survey data.  

Revision History

 This Core Indicator Product webpage is maintained by the Reproductive Health Subgroup.
Date Review Type Author Changes PDF
July 2016 New Indicator Reproductive Health Sub-Group New Indicator

May 4, 2019
Website Update:
No Content Review
Caitlyn Paget,
on behalf of the CIWG 
    No changes made to indicator definitions.
    Migrated to new website structure and format, including:
  • Reorganized content to provide high-level information at a glance, and move in-depth analytic information into dedicated sections for users to access when needed.
  • Renamed "Basic Categories" to "Recommended Subset Analysis Categories"; "Definitions" renamed to "Glossary".
  • Replaced both "Cross-References to Other Indicators" and "OPHS" sections with "Related OPHS Topics" to crosslink with relevant Core Indicators webpages including OPHS program standard(s) and associated indicator(s).
  • Added descriptive sub-headings to the Analysis Checklist and Indicator Comments sections.
  • Removed "Corresponding Health Indicator(s) from Statistics Canada and CIHI" and "from Other Sources" sections.
  • Updated Revision History table, and added PDF copy of previous version for reference.

APHEO's Core Indicators Project has been developed through collaboration across the field of public health in Ontario, 
to provide standardized methodology for population health assessment, to measure complex concepts of individual and community health.
Please contact for further information.