Facts about infertility

Correct timing of certain processes in both the male and female is key for successful conception. There are several steps necessary for a couple to conceive, all of which rely strongly on timing.

The process of conceiving

Throughout her menstrual cycle, a woman’s hormones regulate the development, maturation and release of an egg from her ovary. Every month, the pituitary gland in a woman’s brain sends a hormonal signal to her ovaries to prepare an egg for ovulation. These hormones are known as follicle-stimulating (FSH) and luteinising (LH).

The pituitary gland is controlled by an area of the woman’s brain known as the hypothalamus, which sends out a hormone known as GnRH, or gonadotropin-releasing hormone. GnRH signals the pituitary gland when to release FSH and LH.

This surge of FSH stimulates the growth of the developing follicles and eggs inside the woman’s ovary.

A large increase in LH tells the ovary to release an egg – this is known as ovulation. Normally, only one of a woman’s two ovaries releases an egg during her menstrual cycle.

The egg then moves from the ovary to the fallopian tube and remains viable for approximately 24 hours.

In order to fertilise the egg, a sperm must find its way inside the fallopian tube and penetrate the egg.

If fertilisation is successful, the fertilised egg, or embryo, travels down the fallopian tube into the uterus, where it attaches, or implants, into the lining.

Reproductive system requirements

Both the man and woman’s reproductive systems need to function correctly in order for conception to take place.

In the female, this means:

• Normal ovulation occurs, releasing a viable egg.
• The fallopian tubes are open and functioning correctly, allowing the egg and sperm to meet.
• The fertilised egg is able to travel to the uterus without being blocked from attaching to the wall of the uterus.
• The sperm are able to move through the woman’s vagina, cervix, uterus and fallopian tubes without being blocked in their effort to reach the egg.

In the male, this means:

• The testicles produce viable sperm and male hormone, testosterone.
• The ability to attain an erection and participate in sexual intercourse.
• Normal ejaculation occurs, with semen going through the man’s urethra into the vagina.
• The sperm are correctly shaped and able to move quickly to the fallopian tubes to find and fertilise the egg.

Learning about the common causes of infertility can help you to better understand your situation and seek suitable treatment.

Common causes of infertility in females

Several factors can have an effect on a female’s fertility, including:

• Quality of the uterine lining: e.g. endometriosis can cause damages to reproductive tissue.
• Ability of the ovaries to produce eggs: e.g. ovulation disorders such as polycystic ovarian syndrome (PCOS), which may prevent an egg from being released.
• Fallopian tube structure: e.g. a tubal blockage that prevents the egg and sperm from meeting.
• Age is a major cause of infertility in women, affecting the quality of the eggs and limiting her ability to conceive.

Common causes of infertility in males

The main factors that determine the ability of sperm to fertilise an egg include:

• The number of sperm present.
• Sperm motility (ability to move).
• Direction and quality of movement.
• Sperm morphology (the size and shape).
• Presence or absence of antibodies.
• Integrity of the DNA in the sperm.

Causes of infertility in males may be:

• Structural abnormalities, where either the shape or movement of the sperm is affected, preventing them from finding or binding with the egg.
• Sperm production disorders, where sperm count is reduced or sperm are entirely absent, due to testicular failure or a total obstruction.
• Ejaculatory issues due to ejaculatory failure or impotence.
• Immunological disorders.

A key indication of a woman’s chance to conceive is her age. A woman’s fertility starts to decline at 35 years. By 40, her approximated conception rate is around 8 per cent to 10 per cent each month, and by age 43, it is thought to drop to roughly 1 per cent to 3 per cent each month.

Delayed pregnancy has increased in Western society due to a number of factors. A lot of couples are choosing to start a family only after they have established security both in their relationship and financially, and the amount of late and second marriages is also on the rise.

Bearing a child at 40 or even older is not impossible, but the ability to fall pregnant continues to decline with age, and the risk of chromosomal abnormalities and miscarriage increases. At age 25-29, the risk of miscarriage stands at 10 per cent, whereas it increases to 33.8 per cent for women aged 40-44. Similarly, the risk of a chromosomal abnormality for a woman aged 20 is 1/500 and this increases to 1/20 at for women aged 45.

Why does fertility decline with increasing age?

As a woman ages, the eggs in her ovaries also age, making them less capable of fertilisation and their embryos less able to implant. Ageing, although part of the normal changes that affect all organs and tissues, is the main reason why fertility declines.

With increasing age, fertilisation is associated with a higher risk of genetic abnormalities such as chromosomal disorders. Advanced maternal age also increases the risk of autosomal-dominant diseases such as Marfan’s syndrome, neurofibromatosis and achondroplasia.

As a woman gets older, she has more time to develop gynaecological problems like pelvic infection, tubal damage, endometriosis, fibroids and ovulation difficulties, which will adversely affect her fertility. Sexual function, including libido and frequency of intercourse, tends to decrease with age as well.

The effect of ageing on endometrial receptivity (ability of the endometrium to receive the embryo) is controversial. There is increasing evidence that the receptivity decreases with age.

Older women are more likely to be counselled about the potential complications of pregnancy, such as high blood pressure, bleeding and diabetes.

Ageing does not just affect women but also men, though to a much lesser degree. It affects sperm and coital frequency. However, there is no maximum age at which men are not capable of conceiving a child.

Investigations of infertility in older women

Several tests may be useful in assessing the fertility potential in older women: for example, blood tests to examine the levels of the hormones FSH, LH, estradiol and inhibin on day three of your menstruation. It is advisable to seek the advice of your specialist so investigations and treatment can start.

Chromosomal genetic abnormalities associated with ageing

Each cell in the body has 46 chromosomes; an egg must reduce this number to 23 to combine with the 23 chromosomes that the sperm contributes to the embryo. As a woman gets older, there is more chance that the egg will contain the wrong number of chromosomes. For example, in the disorder Down syndrome, there are three copies of chromosome 21. See the table below for the risks of chromosomal abnormality in newborns by maternal age.

Risk of chromosomal abnormality in newborns by maternal age

Reproductive potential in older women

by P.R. Gindoff and R. Jewelewicz. Fertility & Sterility. 46:989; 1986

Chromosome abnormalities are also the most common cause of miscarriage. The table below shows the risk of miscarriage with increased age.

Risk of miscarriage with increased age

Lifestyle factors, including weight and exercise, have been known to affect fertility. This includes weight levels on both ends of the scale.

Infertility and being underweight

Losing weight or being underweight can lead to a reduction in an important hormonal signal that the brain sends to the ovaries in women, and the testicles in men. This gonadotropin-releasing hormone (GnRH) is produced in the part of the brain called the hypothalamus. The release of GnRH causes the pituitary gland to trigger the hormonal messengers LH and FSH (the gonadotropins). LH and FSH are crucial for the growth of eggs in the ovaries and sperm in the testes.

In mild cases of weight loss, the ovaries may still produce and release eggs, but the lining of the uterus may not be ready to accept a fertilised egg because of insufficient ovarian hormone production. In more severe cases of weight loss, ovulation can cease altogether and menstrual cycles can become irregular or completely absent.

In males, losing weight or being underweight can lead to a decline in sperm function or sperm count. When weight loss is diagnosed as the cause of infertility, treatment often involves ceasing losing weight and even gaining weight if necessary.

Infertility and being overweight

Similarly, being overweight or obese has an effect on hormonal messages to the ovaries and testicles.

For women, increased weight may raise insulin levels, which can result in the ovaries overproducing male hormones, leading to a reduction in egg release. Often, treatment consists of losing weight, and sometimes drugs such as clomiphene citrate or gonadotropins are prescribed to overweight patients. Glucose (blood sugar) levels must be normal in overweight patients before attempting to conceive, and certain metabolic causes of obesity should not be present.

A healthy diet and regular exercise are essential to maintaining good health and weight management.

However, excessive and intense exercise can result in a decline in sperm production and the cessation of ovulation by reducing the brain signal to the ovaries and testes. Generally, running more than 16 kilometres per week is considered too much when trying to conceive. The most effective way to treat reproductive problems associated with extreme exercise is to simply reduce or adjust fitness regimes.