Why Can Only One Sperm Fertilize an Egg?

By Staff WriterLast Updated Apr 14, 2020 5:51:53 AM ET
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According to the National Center for Biotechnology Information, only one sperm normally fuses with an egg because if more than one sperm fuses, through a process called polyspermy, development of the zygote usually stops. In most cases, the egg cell blocks polyspermy.