Top reasons for infertility in women

About 1 in 7 couples in the UK have problems conceiving. (1) That’s 3.5 million people: over 3 times the population of Birmingham. Traditionally, infertility is defined as the inability to conceive after 1 year of trying. However, after 1 year of having regular, unprotected sex, 84 in 100 couples will conceive naturally; after 3 years of trying, that figure rises to 93 in 100 couples. (1)

So why is it that some couples can’t get pregnant?

For one-quarter of couples with fertility issues, a cause cannot be found. (1) In the remaining cases, the problems can be separated into male and female causes. We’ll discuss female fertility issues in this article, however, it’s important to remember that in 40% of couples with fertility issues, both male and female disorders are at play. (1)

Let’s get some background facts straight first. 

Fertility in women essentially comes down to the 3 main parts of the reproductive system: the ovaries, the womb (medically known as the uterus), the Fallopian tubes… and a man’s sperm. The ovaries are two, almond-like structures found on either side of the uterus. They make and store the eggs which are released monthly, known as ovulation. The growth and release of an egg during ovulation are regulated by various hormones in the body. Once released, the eggs travel down the Fallopian tubes into the uterus for potential fertilisation by a male sperm.

Figure 1: Diagram of the female reproductive tract from Pixabay, edited by Emma Hadley.

#1: Ovaries and ovulation

Ovaries and ovulation problems are the most common cause of infertility in women. (2) Fertility is affected by:

      1. The ‘ovarian reserve’: number of eggs stored in the ovaries
      2. The release of eggs during ovulation


Ovarian reserve

Women are born with a finite number of eggs, their ‘ovarian reserve’. The number of eggs in women’s ovaries is fixed while we are still foetuses, at around 5 months of being in babies in the womb, and has already started dropping by the time a baby girl is born! (2) Indeed, several eggs in the ovaries die every month. Once a girl hits puberty, monthly ovulation starts but the monthly decrease in eggs continues. Therefore, over time, there are fewer eggs stored in the ovaries.

What are the reasons why women may have a low ovarian reserve?

    • Age. Due to the monthly death of eggs in the ovaries, older women have a lower number of eggs in their ovaries, making pregnancy more difficult to achieve. The decline in fertility is particularly marked between the ages of 35 and 37, with 1 in 4 women having problems conceiving. This rises to 1 in 3 between the ages of 40 and 44. By the age of 44, the chances of achieving pregnancy are very low. (2) 
    • Tobacco use.
    • Surgery to the ovaries.
    • Certain cancer treatments like chemotherapy or radiation of the pelvis.
    • Rare inherited genetic conditions linked to the X chromosome.



Ovulation problems are caused by problems with the ovaries themselves, or hormone level imbalances in the body. Some causes of ovulation issues include:

    • Menopause: ovulation stops at menopause, so a woman can no longer get pregnant.
    • Polycystic ovary syndrome (PCOS): cysts on the ovaries are underdeveloped and often unable to release an egg, so ovulation cannot take place.
    • Premature ovarian insufficiency: when a woman’s ovaries stop working before the age of 40 but ovulation still occurs occasionally.
    • Hormone problems.
    • Being very overweight or underweight, and excessive exercise all affect hormone balances, and therefore ovulation.
    • Chronic illnesses such as diabetes, chronic kidney disease, thyroid problems.
    • Medication: some chemotherapy medicines, recreational drugs like cannabis and cocaine.


#2: Male subfertility

Male causes are the second main reason couples may have fertility issues. (2) As discussed above, this article will focus on female problems with fertility.

#3 Fallopian tubes

Fallopian tubes are essential to fertility, as they allow the egg to travel from the ovaries into the uterus where it can meet the male sperm for fertilisation. Fallopian tubes can be blocked due to pelvic inflammatory disease following a sexually transmitted infection (STI). They can also be damaged after pelvic surgery, due to the build-up of scar tissue.

#4: Problems with the uterus and surrounding structures

The womb (uterus) is where the female egg meets the male sperm for fertilisation, and where the embryo and later fœtus will develop if fertilisation is successful. Different conditions can affect the uterus and cervix, affecting fertility.

These include:

    • Fibroids: large fibroids can cause the womb to change shape and make implantation of the embryo more difficult.
    • Endometriosis
    • Cervix problems: previous surgery can shorten and scar the cervix. Some women may have cervical mucus defects making fertilisation more difficult.


#5: Other causes

Lifestyle and environment also affect female fertility, often in unknown ways. Exposure to certain pesticides and toxic solvents can decrease fertility. Stress is an important factor in both men and women, as stress can affect the relationship and decrease each partner’s sex drive, and therefore chances of falling pregnant. Finally, lifestyle choices such as smoking, obesity, and excessive alcohol drinking all decrease fertility.

What next?

If you have been trying to conceive for one year without success, you may want to get in touch with your GP. Do consider contacting your GP earlier if you are over 36 years old or either member of the couple has had fertility problems in the past. (3) Your GP will be able to talk through potential causes, investigate these and talk about steps going forward. In the meantime, the best thing you can do is to lead a healthy lifestyle with regular but moderate exercise, maintain a healthy weight and limit alcohol intake. Remember that although many couples may experience fertility problems at some point in their relationship, most couples who keep trying will go on to a successful pregnancy! 


      1. CKS is only available in the UK [Internet]. NICE. [cited 2022 Jan 20]. Available from: https://www.google.com/url?q=https://cks.nice.org.uk/topics/infertility/&sa=D&source=docs&ust=1642710264606884&usg=AOvVaw0TJdGNN9r1iiOwH9cksRzh
      2. Women’s Healthcast – podcast about women’s health by the University of Wisconsin-Madison Department of Obstetrics and Gynaecology 
      3. University of Wisconsin-Madison Department of Obstetrics and Gynaecology. Women’s Healthcast – podcast about women’s health


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