Many sperm functions are crucial in achieving a successful conception.
Challenges the sperm faces
When trying to conceive naturally, the sperms are deposited in the female tract. The first challenge sperms face is to negotiate the mucus in the cervix (neck of the womb). Only very few sperms can travel beyond the cervical mucus and reach the womb. Some will deposit in the fallopian tube and further fewer sperms will make their way towards the egg.
Using complex fine biochemical and cell communication signals, sperms can identify an egg and attach to it (zona pellucida binding). Once attached, the sperms are hyperactivated by complex molecular signalling pathways to enter the egg and start the egg activation process (capacitation and acrosome reaction).
Once inside the egg, sperms uncoil their genetic material. This uncoiled sperm genetic material is finally merged with the genetic material of the egg. Defects in any of these complex events can result in male infertility.
Therefore, the basic semen analysis does not highlight problems in any of the sperm functions that occur after it enters the female tract. It is generally assumed that sperms in sufficient numbers and with defined progressive movement should be able to attach to the eggs.
There are sperm function tests such as sperm penetration tests, sperm viability tests, tests looking into the attachment, and sperm genetic tests. These tests will provide extra information that may add value to the available information. Semen analysis is an evolving science and we are hopeful that there will be better tests in future that will help individualise fertility treatments.