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Transfer of Completely Hatched Euploid Blastocysts Results in Significantly Lower Pregnancy Outcomes Compared to Euploid Expanded or Hatching Blastocysts

AuthorsR.M. James, A. Picou, L. Hansard, H. Werland, M.D. VerMilyea

Objective: To compare pregnancy outcomes between the transfer of PGT-A tested completely hatched blastocysts versus tested expanded or hatching blastocysts in frozen embryo transfers cycles.

Design: Retrospective analysis in a private reproductive technology program.

Materials and Methods: Pregnancy rates between the transfers of completely hatched blastocyst were compared to those of expanded or hatching blastocysts in 676 frozen single embryo transfer cycles occurring from January 2016 through December 2017. Blastocysts in this analysis were all tested for aneuploidy, by NextGen Sequencing. The variable tested was the completeness or degree of the hatching status of the blastocyst at the time of transfer and the presence of fetal cardiac activity via ultrasound at 7 weeks of gestation.

Results: Of 676 euploid embryos included in this analysis, 464 were expanded or hatching (Ex/HgBl) and 212 were completely hatched (CHBl) at the time of transfer. 248 of the 464 (53.45%) HgBl had positive fetal cardiac activity at the 7-weeks compared to 93 of 212 (43.87%) CHBl. Statistical analysis by Chi-square demonstrates a significant difference (p=0.021) between clinical pregnancy rates of the two groups accordingly. Chi-square analysis also demonstrated a significant difference between these two groups with regards to both rates of positive β-HCG and the presence of a gestational sac. Of the 464 Ex/HgBl, 60.56% developed a gestational sac, while 105 CHBl (49.53%) had developed a gestational sac at the 7-week ultrasound (p=0.007). Of the 464 Ex/HgBl transfers, 68.53% resulted in a positive β-HCG test, while 122 of CHBl transfers (57.55%) resulted in a positive β-HCG test (p=0.005). We further evaluated for differences in fetal cardiac activity in different subgroups and found that there was no statistically significant difference in fetal cardiac activity between day 5 versus day 6 Ex/HgBl and CHBl (p=0.38). Similarly, there was no significant difference in fetal cardiac activity rates between Ex/HgBl and CHBl with morphologic grades ≥ BB and < BB (p=0.17).

Conclusions: In frozen embryo transfers with euploid, good morphologic quality embryos, completely hatched blastocyts at the time of transfer resulted in a significantly lower pregnancy success compared to the transfer of expanded or hatching blastocysts. These results suggest that completely hatched embryos may be more fragile, because of the biopsy and vitrification/warming processes and therefore more susceptible to potential cellular damage prior to the time of transfer resulting in lower implantation success. Further analysis needs to be performed to evaluate for additional factors that may contribute to this difference in both implantation rates and continued development of the blastocyst to demonstrate positive fetal cardiac activity. This includes adjusting for maternal age, frozen embryo transfer protocol, endometrial receptivity, and methods of luteal support.

Disclosures: Nothing to disclose

Funding: None