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Spermatogenesis is the process by which haploid sperm cells are produced in the male testes. It starts with stem cells located close to the outer rim of seminiferous tubules. These spermatogonial stem cells divide asymmetrically to give rise to additional stem cells (meaning that these structures “self-renew”), as well as sperm progenitors, called spermatocytes. Importantly, this method of asymmetric mitotic division maintains a population of spermatogonial stem cells in the male reproductive...

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Related Experiment Video

Updated: Jun 29, 2026

Assessing Differences in Sperm Competitive Ability in Drosophila

Assessing Differences in Sperm Competitive Ability in Drosophila

Published on: August 22, 2013

Human live birth and sperm-sex ratios compared.

J Graffelman¹, E F Fugger, K Keyvanfar

¹University Pompeu Fabra, Department of Economics, Barcelona, Spain and Genetics & IVF Institute, 3020 Javier Road, Fairfax, VA 22031, USA.

Human Reproduction (Oxford, England)

|November 5, 1999

Summary

This summary is machine-generated.

The live birth sex ratio slightly favors females, differing significantly from the proportion of Y-chromosome sperm. Male age did not impact the Y-chromosome sperm percentage in this study.

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Published on: June 6, 2019

Area of Science:

Human reproductive biology
Genetics
Human reproductive endocrinology

Background:

The secondary sex ratio at birth typically shows a slight male bias.
Spermatozoa carry either a Y or X chromosome, determining the offspring's sex.
Understanding the factors influencing the sperm sex ratio is crucial for reproductive science.

Purpose of the Study:

To compare the live birth sex ratio with the percentage of Y-chromosome bearing spermatozoa in human semen.
To investigate the relationship between sperm sex ratio and live birth sex ratio.
To assess the influence of male age on the Y-chromosome bearing sperm percentage.

Main Methods:

Semen samples were analyzed to determine the percentage of Y-chromosome bearing spermatozoa.
The live birth sex ratio from the study population was recorded.
Statistical analysis was performed to compare the live birth sex ratio and the sperm sex ratio, and to evaluate the effect of male age.

Main Results:

The live birth sex ratio was approximately 51.3% male.
The overall percentage of Y-chromosome bearing spermatozoa was 50.3%.
The difference between live birth and sperm sex ratios was statistically significant (P < 0.0001), with male age showing no significant effect.

Conclusions:

A significant discrepancy exists between the live birth sex ratio and the proportion of Y-chromosome bearing spermatozoa.
The findings suggest potential biological or environmental factors influencing sex determination post-conception.
Male age does not appear to be a significant factor in determining the Y-chromosome sperm ratio.