Understanding Fertility

Fertility in Women

In women, fertility means the ability to become pregnant and have a baby. A woman's reproductive years begin when she starts her menstrual cycles during puberty (about age 13). The ability to have a child usually ends around age 45, though it's potentially possible for a woman to get pregnant until her periods end with menopause (about age 51).

When a baby girl is born, she already has in her body about 400,000 immature eggs (oocytes). These are stored in her ovaries in tiny fluid-filled sacs called follicles. Once she enters her reproductive years, she starts having monthly menstrual cycles. During each cycle, the ovary releases one egg (or, less commonly, more than one), which may go on to join with a man's sperm cell and begin a pregnancy.

The development and release of the egg depend on a delicate balance of hormones: chemicals that signal the body's organs to do particular jobs. Some of these hormones are produced in the ovaries. Others come from two glands in the brain, the hypothalamus and the pituitary.

Fertility in Men

In men, fertility means the ability to make a woman pregnant. To do this, the man's reproductive system needs to produce and store sperm. It also needs to transport sperm outside of his body, so it can enter the woman's reproductive tract.

The organs that produce sperm are called the testes. Normally a man has two testes, located in the scrotum, the pouch of skin that hangs behind the penis. Each one is called a testis (or sometimes a testicle). Inside each testis are many tiny organs called the seminiferous tubules. This is where sperm develop.

Unlike a woman, who is born with all the eggs she will have in her life, a man makes new sperm continually. Once a man passes through puberty, his stock of sperm is refreshed about every 72 days.

Infertility is the diminished or absent capacity to produce offspring. The term does not imply the complete inability to have children, and should not be confused with sterility. Clinicians have introduced temporal and physical elements to the definition of infertility. Infertility is thus often diagnosed when 1 year of unprotected intercourse has passed without conception.

The Language of Fertility

Fertilisation: contact between sperm and ovum, leading to their union.

Conception: the onset of pregnancy.

Pregnancy: the condition of having a developing embryo or foetus in the female reproductive tract after union of an ovum and sperm.