A guide to infertility in men and women

Infertility refers to the inability of a couple to become pregnant despite having regular, unprotected heterosexual sex for 12 months. Around one in seven couples in the UK experience infertility. 

Infertility can affect both sexes with around a third of all cases being due to the female partner, a third due to the male partner and a third due to both partners. 

While infertility can occur at any age in men and women of reproductive age, the risk increases in women from around age 35 and in men from around age 50. 

Here, we will explore the different types of infertility, how infertility affects men and women and how it is diagnosed, as well as symptoms, risk factors and treatments. 

Types of infertility 

There are three main types of infertility: primary, secondary and unexplained. 

Primary infertility is when a pregnancy has never occurred in the past, and after 12 months of regular (two to three times a week) heterosexual sex, conception has not happened. If the woman is aged 35 or over, the duration for trying to conceive reduces to six months.  

Secondary infertility is the same as primary infertility except that one or more successful pregnancies have occurred in the past.

Unexplained infertility occurs when an underlying cause for infertility has not been identified despite investigations. 

Symptoms of infertility

The defining feature of infertility is an inability to conceive after regular heterosexual sex for a year. However, there may be symptoms that you are infertile or have low fertility prior to this. 

In women, this can include pelvic pain or having painful periods, irregular periods, no periods or a menstrual cycle that is longer than 35 days or shorter than 21 days. 

In men, symptoms of infertility can include symptoms of a hormonal problem, such as reduced body and facial hair, and/or enlargement of breast tissue, and symptoms of sexual function problems, such as difficulty maintaining an erection (erectile dysfunction) and a small amount of semen on ejaculation. 

An inability to smell can also be a sign of infertility in men as this is a symptom of the inherited disorder Kallmann syndrome, which prevents puberty from occurring or completing.

Causes of male infertility

Causes of male infertility can broadly be grouped into problems with sexual function, inherited disorders, hormone imbalances and sexually transmitted infections (STIs). 

Hormonal imbalances

Testosterone levels decrease in men from around age 40. This decrease is gradual with about a 1–2% drop in testosterone levels per year. However, men with diabetes are more likely to have lower than normal testosterone levels for their age.

As well as causing enlarged breasts, low testosterone levels can lead to a reduced sex drive (libido), low sperm count and erectile dysfunction, all of which can contribute to infertility.

Reduced levels of hormones called gonadotrophins, namely luteinising hormone (LH) and follicle-stimulating hormone (FSH), can lead to infertility in men too. These hormones are reduced if a gland at the base of the brain called the pituitary gland is not working properly, for example, due to a tumour. 

Reduced LH levels lower testosterone levels and reduced FSH levels lower sperm count. 

Inherited disorders

The inherited disorder Kallmann syndrome, which affects up to one in 50,000 people, prevents puberty from occurring or completing, resulting in infertility. 

The inherited disorder primary ciliary dyskinesia (PCD), which affects around one in 15,000 people, also causes infertility. PCD reduces the movement of sperm and causes a low sperm count. This reduces the likelihood of a sperm reaching an egg to fertilise it. 

A more common inherited disorder called cystic fibrosis, which affects one in every 2,500 people in the UK, causes infertility in men by preventing sperm from reaching the seminal fluid. Consequently, when the seminal fluid is ejaculated, it does not contain any sperm. 

Sexual function problems

Up to four in 10 cases of male infertility involve varicoceles. Varicoceles refer to swollen veins of the scrotum (the sac that covers the testicles).

Infection of the testicles (orchitis) can also cause infertility, as can infection of the tube that carries sperm out of the testicles (epididymitis). This is because inflammation triggered by an infection can block the transport of sperm. 

Infection of the prostate or injury to the testicles, such as testicular torsion, can lead to infertility by triggering the production of antisperm antibodies. These antibodies cause the body to attack its own sperm. 

Structural problems with the male reproductive system contribute to infertility too. This includes blockages that prevent the transport of sperm, such as a tumour (eg testicular cancer), scar tissue formed after an injury or surgery, or abnormal development. For example, if a male baby or child has undescended testicles, they are more likely to develop fertility problems later in life. 

Diabetes also increases the risk of infertility by damaging the nerves involved in ejaculation. This can lead to retrograde ejaculation where semen enters the bladder instead of being passed out of the penis during ejaculation. 

STIs

The STIs human immunodeficiency virus (HIV), human papillomavirus (HPV) and chlamydia can cause infertility by reducing the quality and number of sperm. 

Additionally, chlamydia can lead to epididymitis, which also increases the risk of infertility. 

Causes of female infertility

Female infertility can be caused by a problem during any stage of the reproductive cycle. 

This starts with the release of an egg from an ovary (ovulation), transport of the egg into the fallopian tube, fertilisation of the egg by sperm that has travelled through the vagina and womb and, finally, the successful attachment and growth of the fertilised egg in the womb. 

Ovulation disorders

Problems with ovulation are the leading cause of female infertility. Ovulation can fail due to several different conditions, including primary ovarian insufficiency where the ovaries stop working before age 40, and polycystic ovarian syndrome (PCOS) where cysts develop on the ovaries causing irregular ovulation. 

Irregular ovulation can also be caused by diabetes and hypothalamic dysfunction. 

Hypothalamic dysfunction interferes with a part of the brain called the hypothalamus. This prevents a gland called the pituitary gland from releasing the correct amounts of hormones that regulate ovulation. 

Severe emotional or physical stress, sudden weight loss or gain and/or being very underweight or overweight can all trigger hypothalamic dysfunction. 

Ovulation may also stop altogether due to a pituitary gland tumour. 

Vaginal and cervical problems

In some women, when semen enters the vagina, it triggers an immune reaction that produces antisperm antibodies. These antibodies destroy the sperm before they can travel onward to fertilise an egg. 

The cervix is the entrance to the womb. If it is too narrow, which occurs in cervical stenosis, sperm can fail to pass through it, which prevents fertilisation of an egg. 

Sperm can also fail to pass through the cervix if the mucus that lines it is too thick. 

Fallopian tube damage

Damage to the fallopian tubes can block the transport of sperm to an egg or block the transport of a fertilised egg to the womb. 

The fallopian tubes can become blocked by persistent inflammation due to pelvic inflammatory disease (PID). The most common cause of PID is STIs, such as chlamydia and gonorrhoea. 

The fallopian tubes can also become blocked due scarring from surgery (eg to treat an ectopic pregnancy or endometriosis), non-cancerous growths (eg uterine fibroids), tumours and accumulation of fluid in the fallopian tubes near the ovaries (hydrosalpinx).

The inherited disorder primary ciliary dyskinesia can impair the transport of an egg and/or sperm through the fallopian tubes. This is thought to be caused by problems with hair-like structures called cilia that line the fallopian tubes.

Problems with implantation

Poor-quality eggs that are fertilised are often not equipped to attach to the womb wall (implantation) or fail to develop after implantation. 

Endometriosis can reduce egg quality and also change the lining of the womb (endometrium) to make implantation less likely. 

Tumours and an abnormally shaped womb can also interfere with implantation.

When to seek help for infertility

If you have tried conceiving naturally for 12 months (or six months in cases where the female partner is aged over 35) but have not become pregnant, see your GP. 

You should also see your GP about infertility if you have had cancer treatment or an STI and are concerned about how this has affected your fertility. 

How is infertility diagnosed? 

It can be helpful for you and your partner to see a doctor so that both of you can have investigations for any potential fertility problems.

Your doctor will ask you questions about your medical history, lifestyle and any symptoms that may be associated with your fertility problems. 

They will ask about any previous pregnancies and/or miscarriages, how long you have been trying to conceive, how often you have sex and whether you have any difficulties during sex. 

A physical examination may also be performed to check for any signs of growths or infection in your pelvic and genital areas. 

They can then refer you for investigations to help identify the underlying cause of your infertility. 

In women, this may involve having blood tests for hormonal imbalances, vaginal swab tests for STIs, and an ultrasound scan to check for growths or scarring affecting the womb, ovaries and/or fallopian tubes. 

In men, this may also involve blood tests for hormonal imbalances, as well as a urine test for chlamydia and semen analysis. 

Infertility treatments

Depending on the results of investigations into your fertility, your doctor may recommend specific treatments. 

For example, in men with low testosterone, testosterone replacement therapy may be recommended, while men with varicoceles can have surgery to remove these swollen veins. There are also several different treatments for erectile dysfunction. 

In women, surgery can be used to remove ovarian cysts, fibroids and excess endometrial tissue that has grown outside the womb due to endometriosis. Antibiotics can be used to treat pelvic inflammatory disease and hormone therapy can help stimulate ovulation. 

If treatment of your underlying health condition does not result in conception, your doctor may recommend assisted conception.

Assisted conception 

Assisted conception includes egg or sperm donation, in utero insemination (IUI), in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI)

Egg or sperm donation can help treat infertility if the cause is due to poor egg or sperm quality. It involves using healthy eggs or sperm donated by a third person. These eggs or sperm can then be used as part of IUI, IVF or ICSI. 

IUI involves placing sperm directly into the womb (uterus) during ovulation. The sperm is first prepared to remove any poor-quality sperm and, therefore, increase the chances of fertilisation. 

IVF involves adding sperm to eggs in a dish or test tube ie outside the body. Both the sperm and eggs are first prepared so that only the highest quality sperm and eggs are used. The sperm are allowed to naturally fertilise the eggs. Several fertilised eggs are then placed in the womb. 

ICSI is similar to IVF except a single sperm is directly injected into a single egg. 

In some cases, these assisted conception treatments may involve a surrogate to carry the pregnancy.

Lifestyle tips to improve your fertility

Leading a healthy lifestyle can improve your fertility, particularly if you are overweight or obese, as carrying excess weight is linked to reduced fertility in both men and women. 

Exercising regularly, following a healthy balanced diet, quitting smoking and avoiding or reducing how much alcohol you drink can all help improve your fertility. You should also practice good sexual hygiene to avoid catching an STI.

As stress can reduce your fertility, it is important to develop practices that help you destress. This could involve mindfulness, yoga or breathing exercises, or taking part in hobbies that help you relax. 

In men, wearing loose underwear can also help as tight underwear can raise the temperature of the testicles, which can reduce sperm quality.