title: Conjoined twins: a worldwide collaborative epidemiological study of the International Clearinghouse for Birth Defects Surveillance and Research.
abstract: Conjoined twins (CT) are a very rare developmental accident of uncertain etiology. Prevalence has been previously estimated to be 1 in 50,000 to 1 in 100,000 births. The process by which monozygotic twins do not fully separate but form CT is not well understood. The purpose of the present study was to analyze diverse epidemiological aspects of CT, including the different variables listed in the Introduction Section of this issue of the Journal. The study was made possible using the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) structure. This multicenter worldwide research includes the largest sample of CT ever studied. A total of 383 carefully reviewed sets of CT obtained from 26,138,837 births reported by 21 Clearinghouse Surveillance Programs (SP) were included in the analysis. Total prevalence was 1.47 per 100,000 births (95% CI: 1.32-1.62). Salient findings including an evident variation in prevalence among SPs: a marked variation in the type of pregnancy outcome, a similarity in the proportion of CT types among programs: a significant female predominance in CT: particularly of the thoracopagus type and a significant male predominance in parapagus and parasitic types: significant differences in prevalence by ethnicity and an apparent increasing prevalence trend in South American countries. No genetic, environmental or demographic significant associated factors were identified. Further work in epidemiology and molecular research is necessary to understand the etiology and pathogenesis involved in the development of this fascinating phenomenon of nature.
authors: Instituto Nacional de Ciencias Médicas y Nutrición "Salvador Zubirán", Departamento de Genética, Registro y Vigilancia Epidemiológica de Malformaciones Congénitas, México City, Mexico. osvaldo@servidor.unam.mx
authors: Osvaldo M
authors: OM
authors: Mutchinick
authors: Leonora
authors: L
authors: Luna-Muñoz
authors: Emmanuelle
authors: E
authors: Amar
authors: Marian K
authors: MK
authors: Bakker
authors: Maurizio
authors: M
authors: Clementi
authors: Guido
authors: G
authors: Cocchi
authors: Maria
authors: M
authors: da Graça Dutra
authors: Marcia L
authors: ML
authors: Feldkamp
authors: Danielle
authors: D
authors: Landau
authors: Emanuele
authors: E
authors: Leoncini
authors: Zhu
authors: Z
authors: Li
authors: Brian
authors: B
authors: Lowry
authors: Lisa K
authors: LK
authors: Marengo
authors: María-Luisa
authors: ML
authors: Martínez-Frías
authors: Pierpaolo
authors: P
authors: Mastroiacovo
authors: Julia
authors: J
authors: Métneki
authors: Margery
authors: M
authors: Morgan
authors: Anna
authors: A
authors: Pierini
authors: Anke
authors: A
authors: Rissman
authors: Annukka
authors: A
authors: Ritvanen
authors: Gioacchino
authors: G
authors: Scarano
authors: Csaba
authors: C
authors: Siffel
authors: Elena
authors: E
authors: Szabova
authors: Jazmín
authors: J
authors: Arteaga-Vázquez
mesh_terms: D000569:Americas / Q000453:epidemiology; D001315:Australia / Q000453:epidemiology; D035843:Biomedical Research / Q000639:trends; D002681:China / Q000453:epidemiology; D000013:Congenital Abnormalities / Q000453:epidemiology* / Q000473:pathology; D004200:Diseases in Twins / Q000453:epidemiology* / Q000473:pathology; D016021:Epidemiologic Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007391:International Cooperation; D008297:Male; D011159:Population Surveillance / Q000379:methods*; D011247:Pregnancy; D015995:Prevalence; D012042:Registries; D012744:Sex Ratio; D014428:Twins, Conjoined / Q000473:pathology; D014430:Twins, Monozygotic