title: The temporary anatomical structures prominent in the first trimester may be fulfilling exchange functions assigned to the placenta in the second and third trimester.
abstract: The extra-embryonic coelom (EEC) and secondary yolk sac are prominent structures in the gestational sac during the first trimester of human pregnancy, at a time before the definitive placental circulation becomes established. We propose that the EEC and yolk sac play a critical role in the nutrition of early pregnancy, fulfilling exchange functions which are assumed by the placenta at a later stage.
authors.affiliation: Department of Obstetrics, St. Bartholomew's Hospital Medical College, West Smithfield, London EC1A 7BE, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Docherty
authors.forename: R K
authors.initials: RK
authors.lastname: Iles
authors.forename: N
authors.initials: N
authors.lastname: Wathen
authors.forename: T
authors.initials: T
authors.lastname: Chard
mesh_terms: D000653:Amniotic Fluid / Q000737:chemistry; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000032:analysis; D008648:Mesoderm / Q000502:physiology; D010920:Placenta / Q000502:physiology*; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000502:physiology*; D011388:Prolactin / Q000032:analysis; D015017:Yolk Sac / Q000502:physiology*
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D011388:Prolactin