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Transfer of nonassisted hatched and hatching human blastocysts after in vitro fertilization
O Khorram1, S S Shapiro, J M Jones
1Department of Obstetrics and Gynecology, University of Wisconsin, Madison 53792, USA. khorram@ob.obgyn.wisc.edu
Objective:
To determine the feasibility of performing blastocyst transfer 6 days after oocyte insemination.
Design:
Retrospective clinical study.
Setting:
University-based IVF center.
Patient(S):
All cases of IVF over a 1-year span of time (June 1998-1999) in which seven 2PN embryos were available for transfer.
Intervention(S):
None.
Main Outcome Measure(S):
Implantation, pregnancy, and multiple pregnancy rates.
Result(S):
Transfer of blastocysts on days 5 and 6 resulted in implantation rates of 69% and 33% (P=0.0006), clinical pregnancy rates of 89% and 59% (P=0.05), and multiple pregnancy rates of 39% and 10% (P=0.03), respectively. In cases in which blastocysts were spontaneously hatching or hatched on day 6 (9% of embryos), implantation and pregnancy rates were 52% and 80%, respectively. Embryos were successfully frozen in the hatched or hatching state with resultant clinical pregnancies.
Conclusion(S):
Transfer of embryos can be delayed to day 6 after oocyte insemination at which time a small percentage of embryos will hatch. Hatching of embryos by day 6 is a favorable prognostic factor for IVF outcome. Embryos that fail to hatch by day 6 may have a lower implantation potential. Difficulty with hatching embryos sticking to the transfer catheter was not encountered. Furthermore, hatching and hatched embryos can be frozen and with subsequent transfer result in pregnancies.