title: The fate of embryos transferred into the uterus.
abstract: OBJECTIVE
  The purpose of this study is to elucidate the fate of embryos transferred into the uterus.
  
  
  METHODS
  Implantation rates were compared between synchronous and asynchronous intrauterine embryo transfers in mice. Then transferred embryos were recovered from the uterus and examined morphologically 24 hr after transfer. Moreover, the same transfer-recovery experiments were performed after ligation of the uterus two-thirds from the uterotubal junction immediately before transfer.
  
  
  RESULTS
  The implantation rate was high (58.4% per embryo, 87.5% per recipient) when blastocysts were transferred into the uteri of recipients of pseudopregnant Day 4, but it was very low (0-2.4% per embryo, 0-8.3% per recipient) when blastocysts were transferred to recipients of pseudopregnant Day 2, or two-cell embryos into recipients of pseudopregnant Days 2 and 4. When transferred embryos were recovered from the uterus 24 hr after transfer, few embryos (1.4%) were recovered in asynchronous transfers, while 66.3% of the embryos were recovered in synchronous transfers. However, from recipients in which the lower portions of uteri were ligated, embryos at more advanced stages were recovered even in asynchronous transfers.
  
  
  CONCLUSIONS
  These results suggest that discharge from the uterus is one of the major causes of the low implantation rate for asynchronous transfer.
authors.affiliation: Department of Gynecology and Obstetrics, Kyoto University Faculty of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Goto
authors.forename: Y
authors.initials: Y
authors.lastname: Noda
authors.forename: M
authors.initials: M
authors.lastname: Shiotani
authors.forename: J
authors.initials: J
authors.lastname: Kishi
authors.forename: T
authors.initials: T
authors.lastname: Nonogaki
authors.forename: T
authors.initials: T
authors.lastname: Mori
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology; D002970:Cleavage Stage, Ovum / Q000502:physiology; D004624:Embryo Transfer / Q000379:methods*; D004717:Endometrium / Q000502:physiology; D005260:Female; D008026:Ligation; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009028:Morula / Q000502:physiology; D010060:Ovulation; D011247:Pregnancy; D011255:Pregnancy Maintenance; D013997:Time Factors