title: Twin-singleton differences in neonatal brain structure.
abstract: Twin studies suggest that global and regional brain volumes are highly heritable. However, estimates of heritability vary across development. Given that all twin studies are open to the potential criticism of non-generalizability due to differences in intrauterine environment between twins and singletons, these age effects may reflect the influence of perinatal environmental factors, which are unique to twins and which may be especially evident early in life. To address this question, we compared brain volumes and the relationship of brain volumes to gestational age in 136 singletons (67 male, 69 female) and 154 twins (75 male, 79 female; 82 DZ, 72 MZ) who had received high resolution MRI scans of the brain in the first month of life. Intracranial volume, total white matter, and ventricle volumes did not differ between twins and singletons. However, cerebrospinal fluid and frontal white matter volume was greater in twins compared to singletons. While gray matter volumes at MRI did not differ between groups, the slope of the relationship between total and cortical gray matter and gestational age at the MRI scan was steeper in MZ twins compared to DZ twins. Post-hoc analyses suggested that gray matter development is delayed in MZ twins in utero and that they experience 'catch-up' growth in the first month of life. These differences should be taken into account when interpreting and designing studies in the early postnatal period.
authors.affiliation: Department of Psychiatry, University of North Carolina, United States of America. rebecca_knickmeyer@med.unc.edu
authors.forename: Rebecca C
authors.initials: RC
authors.lastname: Knickmeyer
authors.forename: Chaeryon
authors.initials: C
authors.lastname: Kang
authors.forename: Sandra
authors.initials: S
authors.lastname: Woolson
authors.forename: J Keith
authors.initials: JK
authors.lastname: Smith
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hamer
authors.forename: Weili
authors.initials: W
authors.lastname: Lin
authors.forename: Guido
authors.initials: G
authors.lastname: Gerig
authors.forename: Martin
authors.initials: M
authors.lastname: Styner
authors.forename: John H
authors.initials: JH
authors.lastname: Gilmore
mesh_terms: D001921:Brain / Q000033:anatomy & histology*; D001931:Brain Mapping / Q000379:methods; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D008297:Male; D009929:Organ Size; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic