The use of intra-endometrial embryo transfer for increasing the pregnancy rate.

It has been demonstrated previously that pregnancy can be achieved by the direct insertion of embryos into the endometrial stroma (intra-endometrial embryo transfer) of mice. In this study we evaluated whether intra-endometrial transfer resulted in a higher pregnancy rate than conventional embryo transfer. Mouse blastocysts (ICR strain), recovered on day 4 of pregnancy, were transferred into pseudopregnant day 2, day 3 and day 4 mice of the same strain; 1-, 2- and 8-cell embryos were also transferred into pseudopregnant day 4 mice. In intra-endometrial embryo transfer, a 27 gauge injection needle was inserted near the utero-tubal junction into the endometrial stroma and then removed; one blastocyst was transferred into each uterine horn with a glass micropipette. Conventional transfers were performed simultaneously as controls. The pregnancy rates and embryonic viability rates were evaluated 9 days after embryo transfer. Furthermore, the rates of live birth for intra-endometrial and conventional embryo transfers were compared when blastocysts were transferred into pseudopregnant day 4 uteri by both methods. In the transfer to pseudopregnant day 2 recipients, the pregnancy and embryonic viability rates were significantly higher (P < 0.01) in intra-endometrial [23.4 (11/47) versus 15.9% (15/94)] than in conventional embryo transfer [4.3 (2/46) versus 2.2% (2/92)]. In the transfer to pseudopregnant day 3 recipients, both rates were also higher (P < 0.01) in intra-endometrial [90.9 (40/44) versus 87.5% (77/88)] than in conventional transfer [67.4 (31/46) versus 64.1% (59/92)].(ABSTRACT TRUNCATED AT 250 WORDS)