Is day 7 culture necessary for in vitro fertilization of cryopreserved/warmed human oocytes?

Abstract

Background: Human embryos are usually cultured to blastocyst stage by Day 5 or 6 after insemination. However, some embryos grow slowly and reach blastocyst stage at Day 7. Acceptable live birth rates have been reported after transfer of Day 7 blastocysts resulted from fresh oocyte in vitro fertilization (IVF). It is unknown whether an extended embryo culture to Day 7 is necessary for cryopreserved oocyte IVF to obtain more transferrable blastocysts. Methods: In this study, 455 oocytes from 57 cycles were warmed, inseminated, and the resulting embryos were cultured by Day 7 to examine blastocyst development after extended culture. Fifty one blastocysts from 16 cycles were biopsied to examine embryo aneuploidies. Results: It was found that 35.1% of the cycles had Day 7 blastocysts, and 3.5% of the cycles had only Day 7 blastocysts. Day 7 blastocysts accounted for 15.6% of total blastocysts. The proportion of top quality of blastocysts was lower at Day 7 than at Day 5 or 6. However, no differences were observed on aneuploid blastocyst rates among Days 5, 6 and 7. Similar clinical pregnancy, ongoing pregnancy and embryo implantation rates were obtained after Day 7 blastocyst transfer as compared with Day 5 or 6 blastocyst transfer. Conclusion: These results indicate that embryos from oocyte warming cycles should be cultured to Day 7 if they do not reach to blastocyst stage by Day 6 so that number of usable blastocysts can be increased.

Efficiency of Autologous Egg Cryopreservation: Eight Years’ Experiences and Clinical Outcomes

“…Recently, Cobo et al used time-lapse scope to track oocyte fertilization and embryo development, they found that pronuclear formation is about 1 h delayed in frozen oocytes as compared with fresh oocytes [48]. We also found that Day 5 blastocyst rates were lower but overall blastocyst rates (Days 5-7) were same between fresh and frozen donor oocytes in a previous study [11,49].…”

Association between duration of progesterone supplementation and clinical outcomes in artificial frozen-thawed embryo transfer cycles

“…Based on these results, it may be concluded that enhanced flexibility would be possible when programming vitrified-warmed embryos transfer after progesterone administration, because no differences were observed between the duration of progesterone administration ≥1 day of embryonic age as far as clinical pregnancy, implantation, live birth, and early pregnancy loss rates are concerned (29,30,36,37). This study demonstrated that there may be no correlation between the developmental stage of the blastocyst and clinical pregnancy in the FET cycle in day 5 embryos or day 6 blastocysts when an equal duration of progesterone supplementation was employed, considering that the duration of progesterone supplementation for day 5 and day 6 blastocysts was equal before FET (48,49). In the light of this result, it could be concluded that clinical pregnancy may not be related to the developmental stage of blastocysts, but rather to the quality of the embryo, as morphologically high-quality day 5 and 6 blastocysts resulted in similar pregnancy outcomes, possibly due to the lack of difference between high-quality embryos on days 5 and 6 regarding aneuploidy (48,49).…”

“…This study demonstrated that there may be no correlation between the developmental stage of the blastocyst and clinical pregnancy in the FET cycle in day 5 embryos or day 6 blastocysts when an equal duration of progesterone supplementation was employed, considering that the duration of progesterone supplementation for day 5 and day 6 blastocysts was equal before FET (48,49). In the light of this result, it could be concluded that clinical pregnancy may not be related to the developmental stage of blastocysts, but rather to the quality of the embryo, as morphologically high-quality day 5 and 6 blastocysts resulted in similar pregnancy outcomes, possibly due to the lack of difference between high-quality embryos on days 5 and 6 regarding aneuploidy (48,49). However, this assumption may be challenged because other data from some scholars indicated that a blastocyst on day 6 has diverse developmental potential and a specific synchronization between the embryo and endometrium with a different WOI compared with a blastocyst on day 5 (50).…”

Clinical outcome analysis of frozen-thawed embryo transfer on Day 7

“…Samer Alfarawati et al (16) found that the rate of aneuploidy was higher among blastocysts with slow development, which was also consistent with our results. Another study (17) suggested that the slow development of D7 blastocysts might be caused by their aneuploid character.…”