Day 3 and day 5 morphological predictors of embryo viability

Abstract

Controlling multiple pregnancies in patients undergoing artificial reproductive procedures requires consideration of single embryo transfers. Therefore, refinements for embryo evaluation are needed that select for the most developmentally competent embryo. The present study was designed to identify day 3 and day 5 morphological predictors of viability following transfers in which the morphology and fate of each embryo was precisely determined. Assessments on day 3 included cell number, and the extent of fragmentation and asymmetry, and on day 5, the developmental stage. Embryos resulting in a viable fetus at 11 weeks gestation were considered developmentally competent. The relationships among individual and collective embryo morphological characteristics were evaluated. Analysis of the interactions among morphological characteristics of embryos transferred on day 3 enabled identification of a multivariable selection order. Assessment of day 5 embryos revealed that expanding and expanded blastocysts exhibited comparable developmental potential that was superior to that of either morulae or early blastocysts. However, expanding or expanded blastocysts derived from 7-cell or 8-cell embryos were developmentally superior to those derived from other cleavage stages, regardless of fragmentation or asymmetry. Collectively, these findings further understanding of morphological predictors of viability, thereby improving the ability to select the most viable embryo for transfer.

Optimal embryo transfer strategy in poor response may include freeze-all

“…than with blastocysts, the patients in the cleavage stage group not only had more embryos transferred per cycle but were also younger than those in the blastocyst transfer group [3]. On the other hand, a number of recent studies have shown significantly higher pregnancy and implantation rates in blastocysts compared to cleavage stage embryo transfers [4][5][6][7][8]. The Cochrane review of 12 randomized controlled trials demonstrated that live birth rates can be optimized by performing blastocyst transfer compared to cleavage stage embryo transfers [9].…”

Is the presence of a non-cleaved embryo on day 3 associated with poorer quality of the remaining embryos in the cohort?

“…Gametes and embryos were maintained at 37°C in a humidified atmosphere of 5 % CO 2 in air as previously described [18,26]. Oocytes were either inseminated within 4-6 h of retrieval or injected 3-5 h after retrieval.…”

“…The fertilization check was performed 16-18 h after insemination or ICSI and zygotes having two pronuclei were cultured individually in 25 μl microdrops of Global medium (IVFOnline, Guelph, Ontario, Canada) supplemented with 5 % human serum albumin. Embryo morphology was assessed on day 3 between 66 and 69 h post-insemination/ICSI using standard criteria of number of blastomeres and extent of fragmentation and blastomere asymmetry [9,18]. Fragmentation scores of 0 through 4 were assigned to each embryo, where scores correlated with 0, 1-9, 10-25, 26-50 % or >50 % fragmentation, respectively.…”

“…While recent studies have investigated the value of time-lapse imaging for embryo assessment and selection [reviewed by 6] standard morphological evaluation remains an important approach for evaluating embryo quality in IVF programs, particularly for those that lack time-lapse imaging systems. In addition, numerous studies have shown a direct correlation between the number of cells in a day 3 embryo and blastocyst formation [11][12][13][14], as well as implantation rates [15][16][17][18][19][20][21]. Indeed, several…”

“…studies have shown that cleavage rates that are either too slow or too fast are associated with a negative impact on implantation rate [15,18,21]. Moreover, arrested zygotes and slow cleaving embryos (two cells on day 2 or 3) are associated with higher rates of chromosomal abnormalities [22].…”