On this page: What factors affect fertility? | What is infertility? | How does reproduction work? | The female reproductive system | The male reproductive system
Many factors can affect a person’s fertility. Fertility problems may be the result of either the woman or the man being unable to conceive, or both.
What factors affect fertility?
Some of the common factors that affect fertility in both men and women include:
- age – fertility naturally declines with age
- weight – being significantly underweight or overweight
- smoking – active and passive smoking can harm reproductive health
- other health issues – endometriosis, fibroids, pelvic disease or cancer.
For more information about how cancer affects fertility, see key questions.
What is infertility?
Infertility is defined as difficulty conceiving (getting pregnant). For women under 35 years of age, the term usually refers to trying to conceive for 12 months; if a woman is 35 or over, the term is used after 6 months of trying.
Infertility is relatively common – it affects one in six Australian couples. Many couples have difficulty coming to terms with infertility. For more information about how infertility can impact emotional health and relationships.
How does reproduction work?
The female and male reproduction systems work together to
make a baby. The process involves two kinds of sex cells (gametes): the female gamete – the ovum – and the male gamete – the sperm.
To have a baby, the ovum needs to be fertilised by a sperm. Each month, from puberty to menopause, one of the ovaries releases an egg (ovum). This is called ovulation.
Ovulation and sperm production are controlled by hormones, which are the body’s chemical messengers that help it work properly. The pituitary gland in the brain produces hormones that stimulate the ovaries to make the female hormones oestrogen and progesterone and to release eggs, and the testicles to make the male hormone testosterone and sperm.
The egg travels from the ovary, down the fallopian tube. Here it can be fertilised by a sperm, which is ejaculated from the penis during orgasm (sexual climax). After the egg is fertilised by the sperm, it’s called an embryo. The embryo then becomes implanted in the lining of the uterus. If the egg is not fertilised, women have a period (menstruation).
Women usually menstruate until the age of 45–55, when monthly periods stop. This is called menopause and happens because
the ovaries stop producing the hormones that are necessary for ovulation. This is the natural end of a woman’s reproductive years. If menopause occurs before age 40, this may be called early or premature menopause.
The female reproductive system
The female reproductive system allows a woman to conceive a baby and become pregnant. It includes the following organs:
- ovaries – two small, oval-shaped organs in the lower abdomen. They contain follicles that hold immature eggs (oocytes), which eventually become mature eggs. The ovaries also make the female hormones oestrogen and progesterone
- fallopian tubes – two long, thin tubes that extend from the uterus and open near the ovaries. These tubes carry sperm to the eggs, and the eggs from the ovaries to the uterus
- uterus (womb) – the hollow organ where a baby (fetus) grows. The inner lining of the uterus is known as the endometrium. The uterus is joined to the vagina by the cervix
- cervix (neck of the womb) – the lower, cylinder-shaped entrance to the uterus. It produces moisture to lubricate the vagina. It also holds a fetus in the uterus during pregnancy and widens during childbirth
- vagina (birth canal) – a muscular tube that extends from the opening of the uterus (the cervix) to the vulva. This is the passageway through which menstrual blood flows, sexual intercourse occurs and a baby is born
- vulva – the collective name for the external part of a woman’s sex organs.
The male reproductive system
The male reproductive system allows a man to father a baby. It includes the following organs:
- testicles – two small, egg-shaped glands that make and store sperm, and produce the male hormone testosterone. This is responsible for the development of male characteristics, sexual drive (libido) and the ability to have an erection
- scrotum – the loose pouch of skin at the base of the penis that holds the testicles
- epididymes – coiled tubes attached to the outer surface of the testicles. The immature sperm travel from each testicle to the epididymis, where they mature spermatic cords and vas deferens – the tubes running from each testicle to the penis. They contain blood vessels, nerves and lymph vessels, and carry sperm towards the penis
- penis – the main external sex organ, through which urine and semen pass
- prostate – a gland that produces the fluid that makes up a large part of semen. It is located near the nerves, blood vessels and muscles that control bladder function and erections
- seminal vesicles – glands that lie close to the prostate and produce secretions that form part of the semen.
Reviewed by: Prof Roger Hart, Medical Director of Fertility Specialists of Western Australia and Professor of Reproductive Medicine, School of Women’s and Infant Health, University of Western Australia, WA; Dr Antoinette Anazodo, Paediatric and Adolescent Oncologist, Sydney Children’s and Prince of Wales Hospitals, Director of the Sydney Youth Cancer Service, NSW; Brenda Kirkwood, 13 11 20 Consultant, Cancer Council Queensland, QLD; Dr Michael McEvoy, Director of Clinical Services, Flinders Fertility, SA; Eden Robertson, Research Officer, Behavioural Sciences Unit, Sydney Children’s Hospital, NSW; Kayla Schmidt, Consumer; A/Prof Kate Stern, Head of Fertility Preservation Service, The Royal Women’s Hospital and Melbourne IVF, Head Endocrine and Metabolic Service, Royal Women’s Hospital and Clinical Director, Melbourne IVF, VIC; and Prof Jane Ussher, Centre for Health Research, Western Sydney University, NSW.