목적: Ionomycin can induce Ca2+ influx by altering the plasma membrane permeability or can act directly on intracellular organelles which release Ca2+. Studies in somatic cell nuclear transfer bovine oocytes showed that ionomycin is a more potent and more specific Ca2+ ionophore than A23187. When ionomycin is used as an assisted oocyte activation agent, the reported fertilization rates are usually higher than with the use of A23187. In humans, calcium fluctuations were detected with a peak shortly before cell division. Interestingly, these calcium oscillations disappeared in arrested embryos. 방법: This prospective study was performed between October 2014 and December 2015 at a reproductive center. All patients involved gave written consent, and institutional review board approval was granted. This study includes 21 non-treatment and 22 treatment couples. A prospective study was conducted including patients with a poor responders following conventional ICSI in our center. In the treatment cycles, all metaphase II-oocytes were exposed to a commercially available ready-to-use 0.5 μM ionomycin for 5 min immediately after ICSI. After a three-step washing procedure, in vitro culture was performed as in the control cycles, when possible up to 8-cell stage. Cleavage and clinical pregnancy rates were compared, p-value of <0.05 was considered statistically significant. 결과: The average female age, number of oocytes retrieved, embryo developmental stage and number of embryos transferred did not vary significantly amongst the groups. Fertilization rate did not differ (75.4 versus 73.2%); however, further cleavage to 8-cell stage was significantly higher (p<0.001) in the ionomycin group (98.5%) when compared with the control cycles (91.9%). Most importantly, clinical pregnancy rates were higher (p<0.01) in the ionomycin treatment group (44.4%) when compared to the control group (20.8%). 결론: The findings of this study indicate that ionomycin treatment improves the rates of cleavage to 8-cell stage and clinical pregnancy in poor responders. However, this treatment does not seem to completely resolve the poor responders. Further investigations are necessary to determine the effects of ionomycin treatment of the culture conditions.