The impact of embryo quality and quantity on implantation and the establishment of viable pregnancies

Abstract

The role of cleavage rates, number of embryos transferred, and some other variables in pregnancy outcome in 222 human embryo transfers was studied. Pregnancy rates were significantly higher in a group of 117 patients receiving at least one embryo that had reached the four-cell stage at 40 hr postinsemination (26% total pregnancies/transfer and 18% ongoing pregnancies/transfer) than in the 105 patients receiving embryos developing at a slower rate (7% total pregnancies/transfer and 2% ongoing pregnancies/transfer). Of the 23 ongoing or term pregnancies produced, 21 came from transfers of at least one embryo that had reached four-cell stage by 40 hr postinsemination. Pregnancy rates were unaffected in either the fast-cleaving or the slower-cleaving embryos by culturing in vitro for an additional 24 hr. The presence of anucleate cell fragments also had no effect on pregnancy rates. Pregnancy rates increased progressively with the transfer of more embryos per transfer. These results suggest that procedures to improve ovulation induction and in vitro embryo culture technique may better the success of in vitro fertilization by providing a high number of rapidly cleaving embryos for transfer.

Pathogenesis, developmental consequences, and clinical correlations of human embryo fragmentation

“…However, although the exact numeric values assigned to fragmentation are subject to inter-and intraobserver variation, the conclusion that the extent of fragmentation and implantation potential are inversely related has been firmly established across all the studies (3,13,45,(47)(48)(49)(50)(51)(52)(53)(54)(55)(56). Staessen et al (57) reported a threshold of 20% fragmentation to demonstrate a difference in implantation rates.…”

“…Apart from the degree of fragmentation, the distribution and size of the fragments are considered to be important (13,(44)(45)(46). A number of distinct fragmentation patterns have been described (13,44), including type 1, few small fragments typically associated with only one blastomere; type 2, many small and localized fragments associated with one or more cells; type 3, small and scattered fragments associated with multiple cells; and type 4, large and scattered fragments associated with several unevenly sized cells.…”

Prognostic value of growth of 4-cell embryos on the day of transfer in fresh IVF-ET cycles

“…Previous studies have shown that pregnancy rates remain low when embryos transferred on day 3 consist of fewer than four blastomeres [3][4][5][6]. Many embryos, however, reach only the 4-cell stage on day 3 and are transferred as such.…”

Biological predictive criteria for clinical pregnancy after elective single embryo transfer

“…Numerous studies have been performed to assess the relationship between embryo quality based on morphologic markers and CPR (7)(8)(9)(20)(21)(22). Embryonic scores have been proposed, usually evaluated by the number and the regularity of blastomeres and on the fragmentation degree (23).…”