Questions? Call0808 2085194orMessage us

Causes of infertility

If you’re having trouble getting pregnant, it can be upsetting and frustrating, especially when you don’t know what’s behind it. Here are the common causes of fertility problems, with suggestions for next steps you can take.

What are the causes of infertility?

What is infertility?

The simplest definition of fertility is when you’re able to make a baby within one year of regular unprotected sex.

Sometimes it can take longer, which doesn’t always mean you’re infertile.

Fertility exists on a spectrum:

  • Optimal fertility - there are little to no delays in getting pregnant

  • Subfertility - it takes longer but is still possible naturally or with fertility treatment

  • Infertility - pregnancy is unlikely without fertility treatment and or donor eggs/sperm

1 in 7 couples in the UK struggle to get pregnant, which can be related to their eggs, their sperm, or both.

Primary vs secondary infertility

There are two types of infertility:

  • Primary infertility – where you’ve never had a pregnancy before and are unable to get pregnant now

  • Secondary infertility – where you’ve had one or more pregnancies in the past but are unable to get pregnant now

Secondary infertility is more likely to be caused by recent conditions or lifestyle factors, instead of a condition you were born with.

tfp-trasferimento-di-embrioni crop

Common causes of infertility in women

Age and egg quality

You’re born with all your eggs, which means that as you age, so do they.

This is why getting older is the most common reason for female infertility.

In your thirties, your fertility starts to reduce until, eventually, you're no longer fertile (around age 45).

At the end of this process is menopause, when your periods stop.

Ovulation problems

Ovulation is when you release an egg, 12 - 16 days before your period.

Infertility is often related to ovulation problems, which can be caused by:

Ovulation might stop completely, or it can become irregular (not every month).

Damaged fallopian tubes or womb

The fallopian tubes are how the egg travels from the ovaries to the womb, so it can be fertilised by sperm.

Conditions that scar or damage the tubes or womb can cause infertility.

These include:

  • Pelvic or cervical surgery such as a C-section

  • Fibroids - non-cancerous growths in the womb

  • Endometriosis

  • Pelvic inflammatory disease - an infection caused by STIs

This can sometimes be reversed with surgery.

Medical treatments

Medicines and treatments that can affect female fertility include:

  • Chemotherapy or radiotherapy to treat cancer

  • Long-term or high doses of NSAIDs like ibuprofen and aspirin

  • Antipsychotic medicines

  • Spironolactone (aka Aldactone), a medicine for fluid retention that can temporarily reduce fertility

Illegal drugs may also affect fertility.

Common causes of infertility in men

Sperm quality

Sperm is considered low quality when there are:

  • Low numbers or no sperm in the semen (azoospermia or oligospermia)

  • Sperm that do not swim properly, making it hard for them to reach an egg

  • Sperm with an abnormal shape, size or appearance

Learn more about male fertility, including how to improve sperm quality.

Problems with testicles

Damage to your testicles can stop you from making healthy sperm.

This can be from:

  • Infections such as STIs

  • Cancer or tumours

  • Congenital conditions (something you were born with)

  • Injury or scrotal injury

It’s not always obvious from looking at them if there’s a problem with your testicles.

Blocked tubes

The tubes that sperm travels through can become blocked, stopping it from leaving the testicles.

Tubes can be blocked due to:

  • Infection

  • Surgery of the bladder, urethra or prostate

  • Swelling

  • Problems with the way the tubes have developed

Medical treatments

Medicines and drugs that can affect male fertility include:

  • Chemotherapy or radiotherapy to treat cancer

  • Anabolic steroids, which are synthetic hormones for medical or personal use

  • Some herbal remedies - cottonseed extract (Gossypol) or Thunder God vine extract (Tripterygium wilfordii)

  • Sulfasalazine (aka Azulfidine) – an anti-inflammatory medicine that can temporarily reduce sperm

Illegal drugs may also affect fertility.

Learn more about fertility conditions

What else affects fertility?

Your lifestyle plays an important part in your overall fertility, including:

  • Weight ­- being above or below your healthy weight

  • Smoking - harmful chemicals impact egg production

  • Alcohol - affects sperm quality

  • Extreme stress - can reduce sperm production or ovulation

Broken cigarette

Fertility tests and when to see a specialist

If you’ve been trying to get pregnant for over a year, a fertility test can help you understand your reproductive health so you can plan your next steps.

You might also consider a fertility assessment if:

  • You’re over 35 and have been trying for 6 months

  • You’re over 40 and want to start trying

  • You have a condition that can affect fertility

  • Your periods have stopped or are irregular


If you’re worried about your fertility or are struggling to get pregnant, a fertility assessment and consultation with a specialist can give you the answers you’re looking for.

Woman holding anatomical drawing
CTA button

See a fertility specialist

We offer fertility assessments for male and female individuals and couples, for fast and accurate fertility insights. We’ll sensitively discuss the problems you’re experiencing and arrange for you to have some tests to identify any problems and help you plan your next steps.

Unexplained infertility


For 1 in 4 couples, the cause of infertility is unknown.

This can be difficult news, leaving you feeling helpless about what to do next.

But it doesn’t mean giving up on your fertility journey.

At TFP Fertility UK, we help many people with unexplained infertility to become parents.

We offer a choice of specialist fertility treatments to suit you and counselling to support you at any point in your journey.

Infertility treatment


Not everyone struggling with fertility has to have treatment to get pregnant.

Some people go on to have a baby naturally - it just takes more time.

But it’s good to know that there are lots of options for you to explore, especially if you’re getting to an age where fertility is a worry.

Treating conditions

If you have a specific condition that affects your fertility, then there are often treatments to ease symptoms or to help conceive.

Conditions that may need treatment include:

The treatment could be surgery or medicine.

Sometimes this is enough to restore fertility, but for other people, fertility treatment is also needed to get pregnant.

Fertility treatment

Fertility treatment is medicine or procedures that have the specific aim of pregnancy, rather than treating the condition itself.

At TFP Fertility, we offer a range of specialist fertility services for:

  • Female and male infertility

  • Individuals or couples

  • LGBTQ + fertility services

We offer full fertility assessments and treatment to help people conceive and have the families they long for, including intrauterine insemination (IUI) and in vitro fertilisation (IVF).

Getting started with fertility treatment.

Woman laughing and holding her daughter while talking to a nurse

Find out more at our fertility events

When it comes to infertility, tests and treatment, there can be a lot to take in. Talk to our friendly experts face-to-face at one of our in-person or online events, and get your fertility questions answered.


What are the signs of infertility?

The main sign of infertility is not being able to get pregnant within a year of having unprotected sex every 2-3 days.

You might not have any other signs any symptoms, as it depends on the cause.

Other signs of female infertility can include:

  • No periods

  • Irregular or missed periods

Other signs of male infertility can include:

  • Problems with ejaculation

  • Cloudy urine after sex

Why have my periods stopped?

There are many reasons why periods can stop.

You should see your GP if you miss three periods in a row.

The most common reasons for missed or stopped periods are:

  • Pregnancy

  • Stress

  • Sudden weight loss

  • Being overweight

  • Too much exercise

  • Taking the contraceptive pill

  • Menopause

  • Polycystic ovary syndrome (PCOS)

Can taking contraception make you infertile?

Contraception does not permanently affect your fertility.

Once you stop taking it, your fertility will eventually return, unless you have reached menopause.

It can take time for your cycle or your fertility to come back after taking contraception.

Our specialists can advise you on how long this might be, as it depends on the type of contraception and how long you took it.

Can an abortion cause infertility?

Having an abortion or miscarriage does not affect your fertility unless you get a complication like an infection.

If you’re worried about pregnancy or fertility after a miscarriage or procedure, speak to one of our expert team for confidential advice and support.

Can STIs and infections cause infertility?

Infections known to cause infertility include:

  • Chlamydia

  • Gonorrhoea

  • HIV

  • Pelvic inflammatory disease

If left untreated, these infections can damage the female and male reproductive organs.

STIs don’t always cause symptoms, which is why it’s important to get tested if you’ve had unprotected sex. 

Not all STIs cause infertility. Herpes and HPV are not linked to infertility.

Is infertility genetic?

As with most health-related concerns, infertility is likely to have a genetic influence.

But for most people, it’s impossible to say for sure whether infertility is caused by their genetics unless they have a specific condition.

Genetic conditions known to cause female infertility include:

  • Turner syndrome (rare)

  • Fragile X syndrome (uncommon)

  • Kallmann syndrome (very rare)

Genetic conditions known to cause male infertility include:

  • Cystic fibrosis (rare)

  • Kleinfelter syndrome (rare)

If you’re worried about a genetic condition affecting your fertility, speak to a specialist.

Does vaping affect fertility?

While smoking is a well-known factor in reduced fertility, there’s less research on vaping.

It’s too soon to say what its long-term effects could be.

So far, it’s not thought to cause infertility.

Vapes are free from tobacco and many other chemicals that are in cigarettes.

But they still contain nicotine, which affects fertility, along with other substances with unknown effects.

So, while vaping may be an alternative to smoking cigarettes, we recommend staying free from all nicotine-based products.


Ready to start your fertility journey? We're here for you

Schedule an appointment to start your fertility journey with us.