Infertility is becoming increasingly more common with recent estimates of 15-20% of couples experiencing infertility some time in their reproductive life.
A typical fertile couple in their mid-to-late 20s, having regular sex, have about a 20-25% chance of conceiving each month. After 6 months at least 3/4 of such couples will be pregnant, and after a year at least 90%. For many people the chance of conception may be lower than normal, but for some people infertility is absolute (there may be no sperm, or the woman’s fallopian tubes may be blocked).
About 25% of infertility is calculated to be directly due to the male partner, and another 15-25% probably also has a male contribution.
The diagnosis of male infertility is usually performed by the observation of sperm under the microscope. Estimates of how many sperm are being produced and their ability to fertilise eggs can be made. However, normal quality semen does not guarantee adequate fertility. The large number of cases of unexplained infertility suggest that abnormal sperm function may be due to genetics.
A recent study has identified a gene expression fingerprint linked with very low pregnancy rates in semen donors with normal semen quality. The researchers analysed semen samples from 68 young and healthy donors whose fertility wasn’t known by looking at the expression profile of 85 genes.
They found significant differences in the expression of individual genes among the eight samples with high and low pregnancy rates. Combining the results of four of these genes gave a much higher sensitivity to recognize subfertile individuals than with the classical analysis of semen (82% vs. 23%).
The results of this study “opens the door to…understanding the causes of infertility of unknown origin and development, in the future, of an additional test to identify individuals of low fertility despite having normal semen values.”
An aside to this: Don’t believe sperm actually swim? I didn’t till I saw them down a microscope so here’s a short clip to show you what they look like
Quick fact: the number of sperm in an ejaculate ranges from 20-400 million per ml.