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Gestational age at birth and school performance

BMJ 2023; 380 doi: (Published 18 January 2023) Cite this as: BMJ 2023;380:p70

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Gestational age at birth and cognitive outcomes in adolescence

  1. Asma Ahmed, postdoctoral fellow1,
  2. Seungmi Yang, associate professor2
  1. 1Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, ON, Canada
  2. 2Department of Epidemiology, Biostatistics and Occupational Health, School of Population and Global Health, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
  1. Correspondence to: S Yang seungmi.yang{at}

Children born before 34 weeks have cognitive deficits unexplained by family characteristics

An estimated 15 million infants are born preterm (<37 weeks’ gestation) worldwide each year.1 Despite much improved survival rates, infants born preterm remain at increased risks of death and multiple short term and long term complications, including cognitive impairments.234 Advanced imaging techniques have identified structural and anatomical differences in the brains of individuals born preterm (compared with those born at term)5 that contribute to cognitive impairments. However, individuals born preterm are not a single homogeneous at-risk group. In a linked paper, Husby and colleagues (doi:10.1136/bmj-2022-072779) report new evidence suggesting that cognitive deficits commonly observed among children born preterm are confined to those born before 34 weeks.6

They examined school grades at the end of compulsory schooling in grade 9 (ages 15-16 years) in a large cohort of nearly 800 000 full Danish siblings born between 1986 …

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