The successful use of pronuclear embryo transfers the day following oocyte retrieval

Lynette A. Scott, Samuel Smith

Research output: Contribution to journalArticlepeer-review


A retrospective analysis of results from 114 initiated in-vitro fertilization cycles utilizing pronuclear embryo transfer is presented. Patients were unselected for age or infertility criteria, constituted a continuous series and were grouped according to response to stimulation (Group 1, ideal; Group 2, suboptimal) or ovarian reserve (Group 3, poor). At 16-18 h post-insemination, embryos were scored for alignment of pronuclei and nucleoli and the appearance of the cytoplasm, generating an embryo score (ES). Transfers were performed 24-26 h post-insemination using two to six embryos with the highest ES. A corrected score was calculated (total score/number of embryos; CS). A total of 114 initiated cycles resulted in 97 oocyte retrievals with 38 clinical pregnancies (39%; 15% implantation). Pregnancy rates were significantly different between the three groups; 37 pregnancies in Group 1 (55% clinical pregnancy; 20% implantation), none in Group 2 and one in Group 3 (6%; 2% implantation: P < 0.001). The ES of transferred embryos correlated with groups. There was a strong correlation between CS and implantation and delivery rates. CS > 15 resulted in a 28% implantation; 65% delivery rate. CS < 14 resulted in four pregnancies, one delivered. The data show that oocyte quality and pronuclear embryo morphology are related to implantation and that pronuclear embryos can be successfully selected for embryo transfer.

Original languageEnglish (US)
Pages (from-to)1003-1013
Number of pages11
JournalHuman Reproduction
Issue number4
StatePublished - 1998
Externally publishedYes


  • Cytoplasmic morphology
  • Nucleoli positioning
  • Pronuclear embryo transfer

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynecology


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