Purpose: This is a retrospective analysis of the morphokinetics, prevalence, and implantation potential of embryos with irregular first and second cleavages as identified by time-lapse microscopy.
Methods: The study included 253 women who underwent 387 assisted reproduction treatments with intracytoplasmic sperm injection (ICSI). Each patient was assigned to one of three groups based on embryo cleavage results. In group I, one to two embryos per cycle showed irregular cleavage; group II, at least three embryos with abnormal cleavage; and in group III (the control group), all embryos cleaved normally. The number of embryos that cleaved from 1 to ≥3 cells or from 2 to ≥5 cells for each patient was recorded. Their prevalence and association with women's characteristics and pregnancy outcome were evaluated.
Results: The prevalence of irregular cleavage was 15.6 % among 1772 ICSI embryos. In 101 cycles, 1-2 embryos per cycle showed irregular cleavage (group I). In 32 cycles, at least 3 embryos showed abnormal cleavage (group II). In 254 cycles, all embryos cleaved normally (group III). The average age of the women in group II was significantly lower in comparison with groups I and III (32.5 ± 4.2 vs. 35.1 ± 4.9 and 35.5 ± 5.1, respectively, p < 0.02). In comparison of groups I and II, the odds ratio for ≥3 embryos with irregular cleavage in women younger than 35 was 3.48 (95 % CI, 1.28 to 9.46). Embryos with irregular cleavage were transferred in 16 women. Three live births were achieved following the transfer of single blastocysts derived from embryos with irregular cleavage from two to five cells.
Conclusions: Early embryos with irregular cleavage are significantly more prevalent in younger women. When these embryos develop to the blastocyst stage, they may have normal implantation potential, leading to the birth of healthy babies.
Keywords: Embryo development; Implantation; Irregular cleavage; Pregnancy; Time-lapse.