title: Intrauterine environment and cognitive development in young twins.
abstract: Intrauterine factors important for cognitive development, such as birth weight, chorionicity and umbilical cord characteristics were investigated. A total of 663 twin pairs completed the Wechsler Intelligence Scale for Children-Revised and scores were available for Performance, Verbal and Total Intelligence Quotient (IQ). The intrauterine factors examined were birth weight, placental weight and morphology, cord knots, cord length and cord insertion. IQ scores for the varying levels of the intrauterine markers adjusting for gender and gestational age were calculated. The heritability of IQ and the association between IQ and intrauterine environment were examined. Twins with lower birth weight and cord knots had lower IQ scores. The aetiology of IQ is largely distinct from that of birth weight and cord knots, and non-shared environment may influence the observed relationships.
authors.affiliation: 1 Department of Clinical Psychological Science, Faculty of Psychology and Neuroscience, Maastricht University, The Netherlands.
authors.forename: E E
authors.initials: EE
authors.lastname: Antoniou
authors.affiliation: 2 Department of Public Health, Heart of Birmingham Teaching PCT, Birmingham, UK.
authors.forename: T
authors.initials: T
authors.lastname: Fowler
authors.affiliation: 3 Department of Neurology, Ghent University Hospital, Ghent University, Ghent, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Thiery
authors.affiliation: 4 Institute of Child Health, University of Birmingham, UK.
authors.forename: T R
authors.initials: TR
authors.lastname: Southwood
authors.affiliation: 5 Centre of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: van Gestel
authors.affiliation: 6 Department of Psychology, Open University of the Netherlands, Heerlen, The Netherlands.
authors.forename: N
authors.initials: N
authors.lastname: Jacobs
authors.affiliation: 5 Centre of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Vlietinck
authors.affiliation: 7 Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University Medical Centre, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van Os
authors.affiliation: 8 King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, London, UK.
authors.forename: F V
authors.initials: FV
authors.lastname: Rijsdijk
authors.affiliation: 5 Centre of Human Genetics, University Hospitals Leuven & Department of Human Genetics, KU Leuven, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Derom
authors.affiliation: 9 Department of Complex Genetics, Cluster of Genetics and Cell Biology, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: M P
authors.initials: MP
authors.lastname: Zeegers