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Caesarean delivery is associated with higher risk of overweight in the offspring: within-family analysis in the SUN cohort
  1. Nerea Martín-Calvo1,2,3,
  2. Miguel Ángel Martínez-González1,2,3,4,
  3. Gloria Segura5,
  4. Jorge E Chavarro4,6,7,
  5. Silvia Carlos1,2,3,
  6. Alfredo Gea1,2,3
  1. 1Department of Preventive Medicine and Public Health, University of Navarra. School of Medicine, Pamplona, Spain
  2. 2Navarra Institute for Health Research, Pamplona, Spain
  3. 3Centro de Investigación Biomédica en Red, Fisiopatología de la Obesidad y Nutrición Instituto de Salud Carlos III., Madrid, Spain
  4. 4Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston Massachusetts, USA
  5. 5University of Navarra. School of Medicine, Pamplona, Spain
  6. 6Channing Division of Network Medicine, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston Massachusetts, USA
  7. 7Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston Massachusetts, USA
  1. Correspondence to Nerea Martín-Calvo, Department of Preventive Medicine and Public Health, School of Medicine, University of Navarra, Pamplona, 31080, Spain; nmartincalvo{at}


Background Most studies assessing the association between caesarean delivery (CD) and childhood overweight/obesity have failed to account for important confounders, such as maternal prepregnancy body mass index (BMI) or the indication of the CD. Furthermore, within-family analyses have reported contradictory results. We aimed at evaluating the association between CD and offspring’s risk of overweight/obesity while adjusting for important confounders and accounting for correlations between siblings.

Methods Women in the ‘Seguimiento Universidad de Navarra’ cohort provided structured information regarding their pregnancy history and their children’s health through online cross-sectional questionnaires. We calculated adjusted differences in BMI z-score and risk ratios (RR) for offspring’s overweight/obesity associated with CD, with hierarchical models to account for correlations between siblings. We also performed a within-family analysis in 341 siblings who were discordant in delivery mode, using conditional multivariable logistic regression.

Results Among the 2791 children analysed, those born by CD had higher average BMI z-scores (difference: 0.17; 95% CI 0.07 to 0.27) and higher risk of overweight/obesity (RR: 1.32, 95% CI 1.05 to 1.65) than children born vaginally. The association did not differ by maternal characteristics or offspring’s age strata, and the results were consistent in sensitivity analyses. Furthermore, within-family analysis showed that children born by CD had 2.67-fold higher risk of overweight/obesity (95% CI 1.10 to 5.12) than their peers born vaginally.

Conclusion Children born by CD have higher average BMI z-scores and higher risk of overweight/obesity than children born vaginally. The consistency of these findings across multiple approaches to address potential residual confounding likely suggests a true biological effect.

  • caesarean delivery
  • overweight
  • obesity
  • offspring

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  • Contributors NMC designed the data collection instruments, collected data, carried out the initial analyses and drafted the initial manuscript. MAM, as the principal investigator of the SUN cohort, coordinated and supervised data collection. GS draft the initial tables of the manuscript. JEC and AG conceptualised the study and critically reviewed the manuscript for important intellectual content. SC reviewed and revised the manuscript. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

  • Funding This work was funded with the National Institute of Health (NIH) grant R01-HD093761. The Sun Study is supported by the Spanish Government-Instituto de Salud Carlos III and the European Regional Development Fund (FEDER) with the grants RD06/0045, PI14/01764 and PI17/01795.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Data availability statement Data are available upon reasonable request.

  • Provenance and peer review Not commissioned; externally peer reviewed.