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Peer-reviewedCC BY-NC-NDJAMA Network Open

Weight Gain During Pregnancy and Severe Maternal Morbidity

  • Sahar Khademioore1
  • Elizabeth K. Darling2,3
  • Rohan D’Souza1,3
  • Giulia M. Muraca1,3
  • Yanfang Guo4,5
  • Laura N. Anderson1
5 affiliations
  1. 1Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada
  2. 2McMaster Midwifery Research Centre, McMaster University, Hamilton, Ontario, Canada
  3. 3Department of Obstetrics & Gynecology, McMaster University, Hamilton, Ontario, Canada
  4. 4School of Epidemiology and Public Health, University of Ottawa, Ottawa, Ontario, Canada
  5. 5Better Outcomes Registry and Network (BORN) Ontario, Children’s Hospital of Eastern Ontario, Ottawa, Ontario, Canada
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Abstract

Importance: Severe maternal morbidity (SMM) carries serious consequences for pregnant individuals, yet the association between gestational weight gain (GWG) and SMM remains poorly understood.

Objective: To examine the association between GWG and SMM across prepregnancy body mass index (BMI) categories.

Design, Setting, and Participants: This retrospective cohort study used linked birth registry data from Better Outcomes Registry & Network Ontario and hospitalization data from the Canadian Institute for Health Information for singleton pregnancies with a hospital delivery at a gestational age of 20 weeks or greater in Ontario, Canada, from April 1, 2012, to March 31, 2022. Data were analyzed from May 1 to November 1, 2025.

Exposures: Continuous GWG as mean weekly gain in the second and third trimesters and categorical GWG (inadequate, adequate, or excessive) according to the 2009 Institute of Medicine recommendations based on prepregnancy BMI.

Main Outcomes and Measures: SMM, defined as a composite of 13 indicators per the Canadian Perinatal Surveillance System, occurring during delivery hospitalization.

Results: Among 1 035 927 pregnancies, 192 731 (18.6%) had inadequate, 296 448 (28.6%) had adequate, and 546 748 (52.8%) had excessive GWG; 15 119 (14.59 per 1000 births) experienced SMM. Compared with adequate GWG, excessive GWG was associated with increased SMM across all BMI categories: underweight (adjusted rate ratio [ARR], 1.33 [95% CI, 1.15-1.53]), normal weight (ARR, 1.24 [95% CI, 1.17-1.31]), overweight (ARR, 1.16 [95% CI, 1.06-1.27]), obesity class I (ARR, 1.21 [95% CI, 1.08-1.35]), obesity class II (ARR, 1.28 [95% CI, 1.07-1.54]), and obesity class III (ARR, 1.24 [95% CI, 1.03-1.48]). Inadequate GWG was associated with increased SMM predominantly among individuals with normal weight (ARR, 1.13 [95% CI, 1.06-1.21]) and overweight (ARR, 1.19 [95% CI, 1.05-1.35]). GWG showed nonlinear associations with SMM across all BMI categories, with risk elevated at both low and high GWG in individuals with underweight, normal weight, and overweight, while in those with obesity classes I to III, risk was concentrated at high GWG values. Estimated SMM rates were lowest at 0.4 kg/wk GWG for underweight through overweight BMI categories and declined across obesity classes to 0.1 kg/wk GWG for the obesity class III category.

Conclusions and Relevance: In this cohort study of 1 035 927 pregnancies, GWG outside Institute of Medicine–recommended ranges was associated with increased SMM risk, with patterns varying by BMI category. These findings may complement existing evidence informing GWG guidance.

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Cite

BibTeXRIS
BibTeX
@article{khademioore2026weight,
  title = {{Weight Gain During Pregnancy and Severe Maternal Morbidity}},
  author = {Sahar Khademioore and Elizabeth K. Darling and Rohan D’Souza and Giulia M. Muraca and Yanfang Guo and Laura N. Anderson},
  journal = {JAMA Network Open},
  year = {2026},
  month = oct,
  doi = {10.1001/jamanetworkopen.2026.40027},
  url = {https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2855699},
  note = {CC BY-NC-ND},
}
RIS
TY  - JOUR
TI  - Weight Gain During Pregnancy and Severe Maternal Morbidity
AU  - Sahar Khademioore
AU  - Elizabeth K. Darling
AU  - Rohan D’Souza
AU  - Giulia M. Muraca
AU  - Yanfang Guo
AU  - Laura N. Anderson
PY  - 2026
DA  - 2026/10/01
JO  - JAMA Network Open
DO  - 10.1001/jamanetworkopen.2026.40027
UR  - https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2855699
AB  - Importance: Severe maternal morbidity (SMM) carries serious consequences for pregnant individuals, yet the association between gestational weight gain (GWG) and SMM remains poorly understood.  Objective: To examine the association between GWG and SMM across prepregnancy body mass index (BMI) categories.  Design, Setting, and Participants: This retrospective cohort study used linked birth registry data from Better Outcomes Registry & Network Ontario and hospitalization data from the Canadian Institute for Health Information for singleton pregnancies with a hospital delivery at a gestational age of 20 weeks or greater in Ontario, Canada, from April 1, 2012, to March 31, 2022. Data were analyzed from May 1 to November 1, 2025.  Exposures: Continuous GWG as mean weekly gain in the second and third trimesters and categorical GWG (inadequate, adequate, or excessive) according to the 2009 Institute of Medicine recommendations based on prepregnancy BMI.  Main Outcomes and Measures: SMM, defined as a composite of 13 indicators per the Canadian Perinatal Surveillance System, occurring during delivery hospitalization.  Results: Among 1 035 927 pregnancies, 192 731 (18.6%) had inadequate, 296 448 (28.6%) had adequate, and 546 748 (52.8%) had excessive GWG; 15 119 (14.59 per 1000 births) experienced SMM. Compared with adequate GWG, excessive GWG was associated with increased SMM across all BMI categories: underweight (adjusted rate ratio [ARR], 1.33 [95% CI, 1.15-1.53]), normal weight (ARR, 1.24 [95% CI, 1.17-1.31]), overweight (ARR, 1.16 [95% CI, 1.06-1.27]), obesity class I (ARR, 1.21 [95% CI, 1.08-1.35]), obesity class II (ARR, 1.28 [95% CI, 1.07-1.54]), and obesity class III (ARR, 1.24 [95% CI, 1.03-1.48]). Inadequate GWG was associated with increased SMM predominantly among individuals with normal weight (ARR, 1.13 [95% CI, 1.06-1.21]) and overweight (ARR, 1.19 [95% CI, 1.05-1.35]). GWG showed nonlinear associations with SMM across all BMI categories, with risk elevated at both low and high GWG in individuals with underweight, normal weight, and overweight, while in those with obesity classes I to III, risk was concentrated at high GWG values. Estimated SMM rates were lowest at 0.4 kg/wk GWG for underweight through overweight BMI categories and declined across obesity classes to 0.1 kg/wk GWG for the obesity class III category.  Conclusions and Relevance: In this cohort study of 1 035 927 pregnancies, GWG outside Institute of Medicine–recommended ranges was associated with increased SMM risk, with patterns varying by BMI category. These findings may complement existing evidence informing GWG guidance.
SN  - 2574-3805
ER  -