Investigating the impact of human seminal fluid on sperm's ability to fertilize eggs, researchers found that seminal plasma can hinder sperm from penetrating and attaching to the egg's protective layers. When sperm were pre-exposed to an environment without seminal plasma, they were able to fuse with eggs even in the presence of seminal fluid. The natural components in seminal plasma seem to disrupt sperm's acrosome reaction and motility, making fertilization less likely when the plasma surrounds the sperm. It appears that certain larger molecules or molecules associated with them in seminal plasma are responsible for interfering with successful fertilization.