A Systematic Review of the Fertilisation Paradigm:From the Theory of Sperm Competition to the Critical Selection of Eggs

Abstract

A classic phenomenon in reproductive biology has historically held that fertilisation occurs purely through biomechanical competition. In this case, it is the fastest and strongest sperm that can eventually fertilise an egg. However, recent research advances fundamentally challenge this reductionist view by proposing the concept of cryptic female choice at the gamete level. This study aims to critically evaluate and systematically examine the paradigm shift from physical competition theory to molecular selection mechanisms, in which the egg actively guides and selects genetically desired sperm using chemoattractant signals. The methodological approach used is Systematic Literature Review (SLR), which refers to the PRISMA systematic reporting guidelines. The evaluation was carried out through a synthesis of literature from 15 major journals that strictly assessed the quality of clinical studies. The results of the literature synthesis showed that human oocytes and follicular fluid release chemotactic agents that differentially modulate sperm navigation based on the compatibility of human leukocyte (HLA) antigen profiles. In conclusion, gamete interactions are not passive races, but highly selective biochemical dialogues. The implementation of these findings has the potential to revolutionise future clinically assisted reproductive technology procedures through biomimetic microfluid-based sperm selection and molecular immunogenetic matching