Infertility is when a couple cannot get pregnant (conceive) despite having regular unprotected sex upto one year.
Around 1 in 7 couples may have difficulty conceiving.
About 84% of couples will conceive naturally within a year if they have regular unprotected sex (every 2 or 3 days).
For couples who have been trying to conceive for more than 3 years without success, the likelihood of getting pregnant naturally within the next year is 1 in 4, or less.
Some people get pregnant quickly, but for others it can take longer. It’s a good idea to see a GP if you have not conceived after a year of trying.
Women aged 36 and over, and anyone who’s already aware they may have fertility problems, should see their GP sooner.
They can check for common causes of fertility problems and suggest treatments that could help.
Infertility is usually only diagnosed when a couple have not managed to conceive after a year of trying.
There are 2 types of infertility:
- primary infertility – where someone who’s never conceived a child in the past has difficulty conceiving
- secondary infertility – where someone has had 1 or more pregnancies in the past, but is having difficulty conceiving again
Read more about how infertility is diagnosed.
Fertility treatments include:
- Medical treatment for lack of regular ovulation
- Surgical procedures such as treatment for endometriosis, repair of the fallopian tubes, or removal of scarring (adhesions) within the womb or abdominal cavity
- Assisted conception such as intrauterine insemination (IUI) or IVF
The treatment offered will depend on what’s causing the fertility problems and what’s available from your local clinical commissioning group (CCG).
Some treatments for infertility, such as IVF, can cause complications.
- Multiple pregnancy – if more than 1 embryo is placed in the womb as part of IVF treatment there’s an increased chance of having twins; this may not seem like a bad thing, but it significantly increases the risk of complications for you and your babies
- Ectopic pregnancy – the risk of having an ectopic pregnancy is slightly increased if you have IVF
Read more about How infertility is treated.
What causes infertility?
There are many possible causes of infertility, and fertility problems can affect either partner. But in a quarter of cases it is not possible to identify the cause.
Common causes of infertility include:
- Lack of regular ovulation (the monthly release of an egg)
- Poor quality semen
- Blocked or damaged fallopian tubes
- Endometriosis – where tissue that behaves like the lining of the womb (the endometrium) is found outside the womb
- Age – fertility declines with age
- Weight – being overweight or obese (having a BMI of 30 or over) reduces fertility; in women, being overweight or severely underweight can affect ovulation
- Sexually transmitted infections (STIs) – several STIs, including chlamydia, can affect fertility
- Smoking – can affect fertility: smoking (including passive smoking) affects your chance of conceiving and can reduce semen quality; read more about quitting smoking
- Alcohol – the safest approach is not to drink alcohol at all to keep risks to your baby to a minimum. Drinking too much alcohol can also affect the quality of sperm (the chief medical officers for the UK recommend adults should drink no more than 14 units of alcohol a week, which should be spread evenly over 3 days or more)
- Environmental factors – exposure to certain pesticides, solvents and metals has been shown to affect fertility, particularly in men
- Stress – can affect your relationship with your partner and cause a loss of sex drive; in severe cases, stress may also affect ovulation and sperm production
There’s no evidence to suggest caffeinated drinks, such as tea, coffee and colas, are associated with fertility problems.
To find out more about what you can do to improve your fertility, see:
- How can I increase my chances of getting pregnant?
- How can I improve my chances of becoming a dad?
Infertility can be caused by many different things. For 1 in 4 couples, a cause cannot be identified.
Infertility in women
Infertility is commonly caused by problems with ovulation (the monthly release of an egg from the ovaries).
Some problems stop an egg being released at all, while others prevent an egg being released during some cycles but not others.
Ovulation problems can be a result of:
- Polycystic Ovary Syndrome (PCOS)
- Thyroid Problems – both an overactive thyroid gland and an underactive thyroid gland can prevent ovulation
- Premature Ovarian Failure – where the ovaries stop working before the age of 40
Cervical mucus problems
When you’re ovulating, mucus in your cervix becomes thinner so sperm can swim through it more easily. If there’s a problem with the mucus, it can make it harder to conceive.
Non-cancerous growths called fibroids in or around the womb can affect fertility. In some cases, they may prevent a fertilised egg attaching itself in the womb, or they may block a fallopian tube.
Endometriosis is a condition where small pieces of the womb lining (the endometrium) start growing in other places, such as the ovaries.
This can damage the ovaries or fallopian tubes and cause fertility problems.
Some women choose to be sterilised if they do not want to have any more children.
Sterilisation involves blocking the fallopian tubes to make it impossible for an egg to travel to the womb.
It’s rarely reversible – if you do have a sterilisation reversed, you will not necessarily be able to have a child.
Illegal drugs, such as marijuana and cocaine, can seriously affect fertility and make ovulation more difficult.
Infertility in men
Semen and sperm
A common cause of infertility in men is poor-quality semen, the fluid containing sperm that’s ejaculated during sex.
Possible reasons for abnormal semen include:
- a lack of sperm – you may have a very low sperm count or no sperm at all
- sperm that are not moving properly – this will make it harder for sperm to swim to the egg
- abnormal sperm – sperm can sometimes be an abnormal shape, making it harder for them to move and fertilise an egg
Many cases of abnormal semen are unexplained.
There’s a link between increased temperature of the scrotum and reduced semen quality, but it’s uncertain whether wearing loose-fitting underwear improves fertility.
The testicles produce and store sperm. If they’re damaged, it can seriously affect the quality of your semen.
This can happen as a result of:
- an infection of your testicles
- testicular cancer
- testicular surgery
- a problem with your testicles you were born with (a congenital defect)
- when 1 or both testicles has not descended into the scrotum (the loose sac of skin that contains your testicles (undescended testicles))
- injury to your testicles
Some men choose to have a vasectomy if they do not want children or any more children.
It involves cutting and sealing off the tubes that carry sperm out of your testicles (the vas deferens) so your semen will no longer contain any sperm.
A vasectomy can be reversed, but reversals are not usually successful.
Some men experience ejaculation problems that can make it difficult for them to release semen during sex (ejaculate).
Hypogonadism is an abnormally low level of testosterone, the male sex hormone involved in making sperm.
It could be caused by a tumour, taking illegal drugs, or Klinefelter syndrome (a rare syndrome involving an extra female chromosome).
Illegal drugs, such as marijuana and cocaine, can also affect semen quality.
In the UK, unexplained infertility accounts for around 1 in 4 cases of infertility. This is when no cause can be identified in either partner.
If a cause for your fertility problems has not been found, talk to your doctor about the next steps.
The National Institute for Health and Care Excellence (NICE) recommends that women with unexplained infertility who have not conceived after 2 years of having regular unprotected sex should be offered IVF treatment.
The NICE guidance has more about unexplained infertility.
Find out more about fertility tests and how problems are diagnosed.