Effect of the presence of trophectoderm vesicles on blastocyst in relation to in vitro hatching, clinical pregnancy, and miscarriage rates.

Trophectoderm vesicles (TVs) are observed in some blastocyststhat penetrate cells from the zona pellucidato the outer margin. Therefore, we compared this incidence in relation to hatching, pregnancy, and miscarriagerates between conventional in vitro fertilization (c-IVF) and intracytoplasmic sperm injection(ICSI). Vitrified/warmed blastocysts(n = 112) were derived from surplus embryos. The blastocystswere then observed using time-lapse cinematographyto resolve the relationship between hatchingand implantation. Another study was conducted that comprised 681 embryo transfer cycles in 533 patients who received a single vitrified/warmed blastocystfrom our clinic. The incidence of TV was significantly higher in embryos inseminated by ICSI compared with c-IVF [ICSI: 51/56 (91 %); c-IVF: 25/56 (45 %); P < 0.01]. The successful hatchingrate was significantly lower in ICSI than in c-IVF [ICSI: 11/56 (20 %); c-IVF: 29/56 (52 %); P < 0.01]. In addition, the hatchingrate was significantly lower when TVs were present (14/76; 18 %) than in non-TV embryos (26/36; 72 %) (P < 0.01). In regard to the clinical study results, no significant differences were found between the groups in the pregnancy rate(TV present group: 107/183, 58.5 %; TV absent group: 273/498, 54.8 %) and miscarriagerate (TV present group: 21/107, 19.6 %; TV absent group: 53/273, 19.4 %). In vivo, we hypothesized that hatchingand hatchedwould occur naturally by assisting protease action in the uterus; therefore, these results suggest that the presence of TV has no effect on pregnancy ratesin the clinical setting.