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Original Investigation
July 21, 2021

Exercise Capacity in Young Adults Born Small for Gestational Age

Author Affiliations
  • 1Fetal Medicine Research Center, BCNatal–Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Déu), Institut Clínic de Ginecologia Obstetricia i Neonatologia, Universitat de Barcelona, Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, Spain
  • 2Institut d’Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
  • 3Pontificia Universidad Javeriana seccional Cali, Cali, Colombia
  • 4BCN Medtech, Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain
  • 5Fetal Medicine Unit, Department of Obstetrics and Gynecology, Hospital Clínico de la Universidad de Chile, Santiago de Chile, Chile
  • 6Institut Clínic Cardiovascular, Hospital Clínic, Universitat de Barcelona, Centre for Biomedical Research on CardioVascular Diseases (CIBERCV), Barcelona, Spain
  • 7Centre de Diagnòstic per la Imatge, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
  • 8Respiratory Medicine Department, Hospital Clínic, Universitat de Barcelona, Centre for Biomedical Research on Respiratory Diseases (CIBERES), Barcelona, Spain
  • 9Philips Research France, Paris, France
  • 10Barcelona Supercomputing Center, Barcelona, Spain
  • 11Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
JAMA Cardiol. 2021;6(11):1308-1316. doi:10.1001/jamacardio.2021.2537
Key Points

Question  Is there an association between fetal smallness and adult exercise capacity or cardiac function and structure?

Findings  In this cohort study of 158 young adults, compared with individuals having birth weights within standard reference ranges, individuals born small for gestational age showed limited exercise capacity, with reduced maximal workload and oxygen consumption, and minor differences in right ventricular geometry at rest.

Meaning  These findings provide evidence suggesting that being born small for gestational age may limit exercise capacity in adulthood.


Importance  Being born small for gestational age (SGA), approximately 10% of all births, is associated with increased risk of cardiovascular mortality in adulthood, but mechanistic pathways are unclear. Cardiac remodeling and dysfunction occur in fetuses SGA and children born SGA, but it is uncertain whether and how these changes persist into adulthood.

Objective  To evaluate baseline cardiac function and structure and exercise capacity in young adults born SGA.

Design, Setting, and Participants  This cohort study conducted from January 2015 to January 2018 assessed a perinatal cohort born at a tertiary university hospital in Spain between 1975 and 1995. Participants included 158 randomly selected young adults aged 20 to 40 years born SGA (birth weight below the 10th centile) or with intrauterine growth within standard reference ranges (controls). Participants provided their medical history, filled out questionnaires regarding smoking and physical activity habits, and underwent incremental cardiopulmonary exercise stress testing, cardiac magnetic resonance imaging, and a physical examination, with blood pressure, glucose level, and lipid profile data collected.

Exposure  Being born SGA.

Main Outcomes and Measures  Cardiac structure and function assessed by cardiac magnetic resonance imaging, including biventricular end-diastolic shape analysis. Exercise capacity assessed by incremental exercise stress testing.

Results  This cohort study included 81 adults born SGA (median age at study, 34.4 years [IQR, 30.8-36.7 years]; 43 women [53%]) and 77 control participants (median age at study, 33.7 years [interquartile range (IQR), 31.0-37.1 years]; 33 women [43%]). All participants were of White race/ethnicity and underwent imaging, whereas 127 participants (80% of the cohort; 66 control participants and 61 adults born SGA) completed the exercise test. Cardiac shape analysis showed minor changes at rest in right ventricular geometry (DeLong test z, 2.2098; P = .02) with preserved cardiac function in individuals born SGA. However, compared with controls, adults born SGA had lower exercise capacity, with decreased maximal workload (mean [SD], 180 [62] W vs 214 [60] W; P = .006) and oxygen consumption (median, 26.0 mL/min/kg [IQR, 21.5-33.5 mL/min/kg vs 29.5 mL/min/kg [IQR, 24.0-36.0 mL/min/kg]; P = .02). Exercise capacity was significantly correlated with left ventricular mass (ρ = 0.7934; P < .001).

Conclusions and Relevance  This cohort of young adults born SGA had markedly reduced exercise capacity. These results support further research to clarify the causes of impaired exercise capacity and the potential association with increased cardiovascular mortality among adults born SGA.

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