Background: Despite the different types of treatment options that assisted reproductive technology (ART) has to offer, and the almost optimised culture media available, there are still patients where delayed or decreased rates of fertilisation become apparent over a number of ICSI cycles. In vivo, phospholipase C zeta, which is excreted by the sperm, is thought to be responsible for oocyte activation. Normally this substance is released into the ooplasm where phosphatidylinositol-bisphosphate is then split into diacylglycerine and inositol triphosphate (IP3). The latter molecule then binds to its receptor in the endoplasmic reticulum, thereby initiating the release of calcium and starting off a calcium oscillation. Even a tiny error in this process will prevent this oscillation from being initiated and will therefore result in failed fertilisation.Another very important factor required for successful fertilisation is human serum albumin. Nowadays, human serum albumin is included in nearly all culture media and calcium ionophores available. However, as serum albumin is obtained from the blood of patients, there is always the risk of contamination with an infectious disease.Approach:This Master thesis portrays the importance of Ca2+ ionophores. With the help of the ionophore, the calcium level within the oocyte can be maintained and can thereby decrease the chances of a failed fertilisation. Furthermore, my Master thesis covers the necessity of HSA in calcium ionophores.Result: The results of this Master thesis show that omitting HSA from the Ca2+ ionophore solution does not have a negative impact on fertilisation or pregnancy rates. A reason for this could be that the fertilised oocyte is only incubated in the solution for 15 minutes. The culture medium, in which the embryo is incubated in until the time of the transfer, contains a sufficient amount of HSA.