The effects of fertilization mode, embryo morphology at day 3, and female age on blastocyst formation and the clinical outcomes

Abstract

(2015) The effects of fertilization mode, embryo morphology at day 3, and female age on blastocyst formation and the clinical outcomes, Systems Biology in Reproductive Medicine, 61:1, 50-56, DOI: 10.3109/19396368.2014 AbstractThe aim of this study was to evaluate the influence of in vitro fertilization (IVF) versus intracytoplasmic sperm injection (ICSI), fertilization mode embryonic morphology at day 3, and female age on blastocyst development, on the clinical outcomes of pregnancy after blastocyst transfer. A total of 471 cycles were retrospectively investigated. The rates of blastocyst formation and of good blastocyst morphology were higher in IVF than in ICSI cycles but there were no significant differences in the clinical pregnancies or in the miscarriage rates. The rates of formation of blastocyst and of blastocysts with good morphology were significantly higher from good-morphology embryos than from poor-morphology embryos. Nevertheless, 16.9% of the poor-morphology embryos reached the blastocyst stage. The total rates of blastocyst formation, and rates of clinical pregnancy and implantation were statistically similar in the age 535, 35-39, and 439 year groups, although tending to decrease with increasing age. When equal numbers of embryos were transferred on day 3, the rates of clinical pregnancy and implantation after blastocyst transfer were significantly higher in the 535 year age group than in the 35-39 and 439 year age groups, which were not significantly different. The miscarriage rates after embryo or blastocyst transfers were not statistically different in groups of similar age. Therefore, extended embryo culture up to the blastocyst stage could be implemented for women aged younger than 35 years to increase the pregnancy rate. For older women, transfer and vitrification of available embryos at day 3 and extended culture of morphologically poor embryos to the blastocyst stage for cryopreservation may improve the clinical outcome.

Increased pregnancy outcome after day 5 versus day 6 transfers of human vitrified-warmed blastocysts

“…However, there was an important difference compared with our study, in which all embryos vitrified on D5 or D6 were warmed on D5 progesterone and transferred after 2 or 3 h. There is limited information on the reasons why blastocysts with delayed blastulation exert a lower clinical outcome. In addition to metabolic imbalances and bioenergetics issues, higher aneuploidy rates in slow growth embryos have been proposed as a possible explanation (Capalbo et al, 2014;Yin et al, 2015). Taylor et al (2014) calculated that blastocysts that formed and were vitrified on D6 (slow developing embryos) had a 10% increase in aneuploidy rates compared with those that formed on D5, and this difference might be the reason for their lower pregnancy outcome after vitrified-warmed transfer.…”

A predictive model for high-quality blastocyst based on blastomere number, fragmentation, and symmetry

“…Higher implantation and pregnancy rates allow the transfer of a single blastocyst to reduce the risk of multiple gestations [5,21]. Meanwhile, the top day-3 embryos also have an optimistic pregnancy rate [8]. It has been reported that day-3 embryo transfers with more than two eight-cell-stage embryos and less than 20% fragmentation appear to have a similar implantation rate as the blastocyst transfers [23], and blastocysts do not improve the cumulative pregnancy rate [24][25][26][27].…”

“…Although embryo evaluation criteria can help us select embryos [4], scholars have further claimed that the implantation rate and pregnancy rate for blastocysts are higher than those for embryos, indicating that blastocyst transfer is more advantageous than day-3 embryo transfer, particularly for high-quality blastocysts [5,6]. It has also been reported that a good day-3 embryo is apt to form a high-quality blastocyst [7,8]. However, not all good day-3 embryos can form high-quality blastocysts, partly because of the negative effect of being exposed to in vitro conditions for a long time [9].…”

Ultrastructure of cytoplasmic fragments in human cleavage stage embryos

“…There are several reports on reduced pregnancy outcomes from transferring embryos with poor morphology [29,30]. Some embryo dysmorphisms, however, like cytoplasmic fragments and coarse granulation in PVS, could be removed from to degeneration or lysis of healthy neighboring blastomeres [14].…”