Comparing early embryo morphokinetics with time-lapse microscopy in patients with low and normal ovarian response to ovarian stimulation.

In this retrospective study, patients undergoing ovarian stimulation were allocated into two groups (47 normal responders (NR) vs 47 low responders (LR)) according to the number of aspirated oocytes and their Anti-Müllerian hormone (AMH). 171 oocytes were retrieved from the LR group and 447 oocytes from the NR group. The oocytes were studied regarding the early embryo morphokinetic parameters and cleavage stage patterns after data extraction from our EmbryoScope database. The following parameters were recorded; time of PN fading (tPNf), time to two cells (t2), three cells (t3), four cells (t4), asynchrony in 2 cell cycle (S2), fragmentation, multinucleation, direct cleavages from 1 to 3 cells, reversed cleavage, rolling and non-tetrahedral shape. Except of an indicative time difference in t3 (dif = 0.884; p-value < 0.046), the differences in timings of early cell divisions were not statistically significant when tPNf was used as a starting point and the analysis was adjusted for age. No statistically significant differences were observed for irregular cleavage patterns, multinucleation at 2-cell stage, fragmentation and non-tetrahedral shape rate at the 4-cell stage. However, the risk for multinucleation at 4-cell stage is significantly lower in low responders (OR = 0.342; p-value < 0.019). The groups did not differ regarding fertilization and cleavage rates as well as the number of embryos that fulfill the European Society of Human Reproduction and Embryology (ESHRE) criteria for top quality characteristics on Day 2. Embryos derived from patients with low ovarian response have similar morphokinetic characteristics and cleavage stage pattern as embryos from patients with normal ovarian response.