The best swimmer will not win if the judge has her own rules

The most common disease among 22-44 year olds is infertility. According the International Classification of Diseases (ICD 11) definition for infertility is “a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse”. This also is WHO definition of male and female infertility.

Illnesses, such as mental illness (lasting more than 6 months) asthma or diabetes are generally far behind infertility in this age group.

The causes of infertility have been studied for over 100 years. Either the causes of infertility are due to a man, or a woman, or both, or the cause remains unclear or unknown. Depending on the source, the cause is found in about 30-50% of cases in men, and about 30-50% in women, too. The difference in the different sources is explained by how the fact that the cause is found in both is classified. About 10-30% of the cause remains unclear or unknown.

A study published this year (Fitzpatrick et al. 2020) may give some light on this ‘cause unknown’. According to their research, it may be that a woman’s egg actually ultimately chooses with whom she wants to conceive. The sperm does not choose. His function is only to fertilize.

The choosing process of woman’s egg is pure biological and chemical process that has nothing to do with love. So women, the man you have chosen and you love, may have been rejected by your egg: he might not be the choice of your egg, even if you wanted to. On the other hand, the man you hate or fear, such as a violent man or for example after a rape, may indeed be the choice of your egg. Everyone has heard stories of couples who have tried a child for years without success. But after resigning, both of them have had their own children. There could also be a scientific explanation for this phenomenon, and there is no reason to blame the neighbor.

So it is good to remember that a woman’s egg ultimately chooses whom she likes.



Fitzpatrick, J.L., Willis, C., Devigili, A., Young, A., Carroll, M., Hunter H.R. & Brison D.R. 2020. Chemical signals from eggs facilitate cryptic female choice in humans. Proceedings of Royal Society B 278: 20200805.,


Jouni Tuomi, PhD, Principal Lecturer,

Tampere University of Applied Sciences

Tampere, Finland



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