Infertility

Overview

The Mechanism of Normal Conception

Normal conception occurs when a sperm fertilises the egg (ovum) in a woman's Fallopian tube.

This process is highly complex and to a large extent still not completely understood. However, in simple terms, it can be seen from Figure that the process requires the production, maturation and release of both male and female gametes (sperm and egg respectively) and their subsequent transport and joining together (fertilisation). Fertilisation takes place within the Fallopian tube and not in the uterus (womb) as many people believe. Failures at any stage in this process occur commonly and this is one of the many reasons that human beings naturally can take so long to conceive, but if the failures continue to occur this will lead to infertility. An embryo (the earliest stage of the child) is formed once the ovum has been fertilised and starts to divide. The embryo then migrates back along the tube into the uterus where following repeated cell division it reaches the blastocyst stage. The blastocyst must them escape from its protective covering the Zona Pellucida and this process is called hatching, Once it has hatched the embryo can them burrow into the already hormonally prepared uterine lining, a process called implantation. Provided all is normal a child will ultimately develop and grow.

It is vital to understand that in normal healthy fertile couples, not all sperm are fertile and neither are all eggs. In addition once an egg is fertilised and an embryo forms once again in nature not all embryos will survive and travel to the uterus, nor implant, nor will lead to a live baby! Therefore an egg or sperm or embryo represents a chance at reproduction but not a certainty. This selection process is probably part of nature's way of ensuring that only the best reproductive outcome is assured in most couples.

It is interesting to note that all these events and changes will have occurred before the woman misses her first period.

To simplify the matter, therefore, in order that a couple may have a chance of conceiving, the following basic requirements must be fulfilled:-

• Normal sperm (MALE)
• Normal eggs (FEMALE)
• Normal pathway (vagina cervix uterus tube(s) and ovaries)