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Updated: May 4, 2026
Minimally Invasive Embryo Transfer and Embryo Vitrification at the Optimal Embryo Stage in Rabbit Model
Published on: May 16, 2019
IVF outcome is optimized when embryos are replaced between 5 and 15 mm from the fundal endometrial surface: a
Valentina Rovei, Paola Dalmasso, Gianluca Gennarelli
1Physiopatology of Reproduction and IVF Unit, Department of Surgical Sciences, University of Torino, Sant'Anna Hospital, Torino, Italy. fertisave@yahoo.com.
Background:
Some data suggest that the results of human in vitro fertilization (IVF) may be affected by the site of the uterine cavity where embryos are released. It is not yet clear if there is an optimal range of embryo-fundus distance (EFD) within which embryos should be transferred to optimize IVF outcome.
Methods:
The present study included 1184 patients undergoing a blind, clinical-touch ET of 1-2 fresh embryos loaded in a soft catheter with a low amount of culture medium. We measured the EFD using transvaginal US performed immediately after ET, with the aim to assess (a) if EFD affects pregnancy and implantation rates, and (b) if an optimal EFD range can be identified.
Results:
Despite comparable patients' clinical characteristics, embryo morphological quality, and endometrial thickness, an EFD between 5 and 15 mm allowed to obtain significantly higher pregnancy and implantation rates than an EFD above 15 mm. The abortion rate was much higher (although not significantly) when EFD was below 5 mm than when it was between 5 and 15 mm. Combined together, these results produced an overall higher ongoing pregnancy rate in the group of patients whose embryos were released between 5 and 15 mm from the fundal endometrial surface.
Conclusions:
The site at which embryos are released affects IVF outcome and an optimal EFD range exists; this observations suggest that US-guided ET could be advantageous vs. clinical-touch ET, as it allows to be more accurate in releasing embryos within the optimal EFD range.
