CSI’s method of directly introducing sperm into an egg defeats the natural process of only a select few sperm making it to and fertilising an egg. This can be a disadvantage because this selection process is nature’s way of making sure that the best sperm with the best genetic material are the ones with the best chance at fertilising an egg. Removing that selection process can lead to an increase risk of developmental and health issues for ICSI children, as well as a higher risk of miscarriage because of the poorer genetic material involved