When a girl is born, her ovaries contain approximately two million female gametes, called oocytes (or eggs). At puberty, the pituitary gland, located in the central part of the brain, starts making hormones that stimulate the ovaries to produce female sex hormones such as oestrogen and progesterone. The secretion of these hormones causes a girl to develop into a sexually mature woman. Towards the end of puberty, girls begin to release the oocytes as part of a process called the menstrual cycle. For more information, see our resource article on ‘the menstrual cycle’.
An oocyte is released from either one of the ovaries approximately once per month in a process called ovulation. The oocyte can survive for approximately 24 hours, during which time it moves into the fallopian tube and awaits fertilisation by a sperm. While this is occurring, the lining of the uterus (the endometrium) is thickening and preparing to accept and nurture an embryo.
If sex occurs, the sperm travel from the vagina through the neck of the cervix, through the uterus and along the fallopian tubes to meet the oocyte. Once the oocyte is fertilised by a sperm, an embryo is created. Over the next four to six days, the embryo moves down the fallopian tube to the uterus where it attaches to the lining in a process called ‘implantation’ and hopefully flourishes during a healthy pregnancy.
If fertilisation does not occur, the oocyte dries up and leaves the body along with the blood and tissues from the inner lining of the uterus about two weeks later. This process is called menstruation (or period). The whole process of ovulation generally repeats again in the next month, giving rise to another fertile period and a chance of achieving a pregnancy.
A female’s chance of achieving a pregnancy can be affected by:
Females are born with all of the oocytes they will ever have. By the time of the first menstruation, this number will have dropped to approximately 300,000. Once a female reaches the age of 35, her fertility begins to decline. Not only does the number of oocytes decrease, but the quality of the oocytes that are left also diminishes. For more information, see our resource article on the impact of age on fertility and our medical director in the media raising awareness of the impact of age on fertility.
The delicate and narrow fallopian tubes can easily become blocked or damaged. This can result in problems with the sperm reaching the oocyte, interfering with embryo development and uterus implantation. Surgery can sometimes treat tubal infertility but if this is not possible, or if surgery is unsuccessful, in vitro fertilisation (IVF) may be recommended.
This is a condition in which the tissue (endometrium) that normally lines the inside of the uterus grows in places in the pelvis where it doesn’t belong, such as on the ovaries, fallopian tubes, outside of the uterus. This tissue acts the same as that found in the uterus and responds to changes in hormones during the menstrual cycle, resulting in the tissue breaking down and bleeding. This can cause pain before and after menstruation, may cause the formation of scar tissue and adhesions (organs sticking together). Treatment may involve medications, surgery or fertility treatment, such as in vitro fertilisation (IVF). For more information see our resource article on endometriosis.
If the menstrual cycle is irregular or absent, the production and release of oocytes may be affected. About 40 percent of women who are infertile will have problems with ovulation. Infrequent periods (oligomenorrhoea) or the absence of periods (amenorrhoea) are most often caused by deficiency in one of the controlling hormones and may be able to be treated with medications.
Uterine fibroids or uterine myomas occur more frequently with advancing age. A fibroid is a non-cancerous growth of the muscle in the uterus. These may require treatment if they are causing problems with fertility.
This is a condition in which too many male hormones (androgens) are produced by the ovaries. This causes the ovaries to become enlarged, with a smooth but thicker than normal outer surface. Many small cysts cover this surface, which are themselves harmless, but may cause infrequent or absent periods, impacting fertility. The condition may be treated with medication. Larger cysts may need to be surgically removed. For more information, see our resource article on polycystic ovarian syndrome (PCOS).
Some forms of medical treatment, particularly chemotherapy and radiotherapy, can have an adverse effect on fertility in women. For more information, see our resource articles on ‘fertility preservation options for females’ and ‘fertility preservation options for males’.
Also known as idiopathic infertility, this is defined as not being able to conceive after one year, even though the menstrual cycle is normal, semen is normal, and the results of fertility examinations are normal.
Today, there are a number of assisted reproductive technology (ART) treatments available to help overcome difficulty conceiving. Read more about fertility and treatment options.View our fertility and treatment options
When a male reaches sexual maturity, the two testes produce and store millions of male gametes each day, called sperm. The testes also produce the male sex hormones, such as testosterone. The sperm move into the epididymis to complete their development. It takes about 70 days for sperm to be produced and become mature. The male reproductive accessory glands, such as the seminal vesicles and prostate gland, produce a white liquid called seminal fluid, which mixes with the mature sperm during transit to form semen.
At the time of ejaculation, muscles around the reproductive organs contract and force the semen through the duct system, out of the male’s body through his urethra: a process called ejaculation. Each ejaculate can contain up to 500 million sperm.
When the male ejaculates during intercourse, semen is deposited into the female’s vagina. From the vagina, the sperm make their way up through the cervix and move through the uterus with assistance from uterine contractions. If a mature oocyte (egg) is in one of the female’s fallopian tubes, a single sperm may penetrate it, and fertilisation occurs, creating an embryo. Over the next four to six days, the embryo moves down the fallopian tube to the uterus where it attaches to the lining in a process called implantation, and hopefully flourishes during a healthy pregnancy.
A male’s fertility potential can be affected by a number of conditions, such as:
These can be due to a number of factors such as an infection, failure of the testes to descend at birth (undescended testes), genetic causes, torsion (twisting of the testis in the scrotum), varicocele (varicose veins of the testes) or damage as a result of medicine, chemical or radiation.
This can be due to an infection, absence of the vas deferens, an accessory gland problem or as a result of a prior vasectomy.
This may be the result of premature ejaculation, failure of ejaculation, erectile dysfunction, spinal cord injury or damage to nerves.
These can be due to pituitary tumours or problem, or anabolic (androgenic) steroid abuse.
This can be the result of an injury or infection in the epididymis, a prior vasectomy or for unknown reasons.
Today, there are a number of assisted reproductive technology (ART) treatments available to overcome difficulty conceiving. Read more about fertility and treatment options.View our fertility and treatment options
Same Sex Couples
Advances in reproductive technologies mean there are now more options than ever for lesbian, gay, transgender and intersex people wanting to fulfil their dream of having a child and building a family.
Many same-sex couples will not have a fertility problem and our team can discuss using the mildest form of fertility treatment to conceive. Donor sperm can be used for either intrauterine insemination (IUI) or in vitro fertilisation (IVF).View our fertility and treatment options
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