title: Term and postterm twin gestations. Placental cause of perinatal mortality.
abstract: OBJECTIVE
  To compare perinatal mortality in twins and singletons and to study the influence of fetal sex, placentation and maternal parity on perinatal mortality in term and postterm twin gestations.
  
  
  METHODS
  The subjects of the study were 1,511 twin pairs and 3,022 singletons. All were born at a gestational age of 27 weeks or more in two clinics in Amsterdam between 1931 and 1975.
  
  
  RESULTS
  Perinatal mortality was lower in twins than in singletons until 37-38 weeks and higher afterwards. In twins, perinatal mortality was higher in boys than in girls, in monochorial than in dichorial twins, and in primiparae than in multiparae, especially in the last trimester.
  
  
  CONCLUSIONS
  The development of the twin placenta may set limits in term and postterm twin gestations and may be responsible, to some extent, for the increase in perinatal mortality.
authors.affiliation: Department of Obstetrics and Gynecology, University of Amsterdam, The Netherlands.
authors.forename: O P
authors.initials: OP
authors.lastname: Bleker
authors.forename: H
authors.initials: H
authors.lastname: Oosting
mesh_terms: D005260:Female; D005313:Fetal Death / Q000209:etiology*; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D008297:Male; D010298:Parity; D010929:Placentation; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D014427:Twins