Understanding the Causes of Infertility-image

Understanding the Causes of Infertility

Despite what we may have been led to believe by our teachers and society, getting pregnant is often not as easy as we may think. For many, the journey to parenthood can be a  challenging process, both physically and emotionally. As many as 1 in 7 heterosexual couples experience infertility in the UK, yet the causes are sometimes preventative, or treatable. We’re here to help you understand the different causes of infertility, and the options available for those who need support.


Defining Infertility

Infertility is defined as the inability to conceive within a year of trying, despite having regular unprotected sex with your partner. There are 2 types of infertility:

  • Primary infertility: If you have never conceived a child previously and have difficulty falling pregnant. 
  • Secondary Infertility: If you have had 1 or more pregnancies in the past, however, you are struggling to conceive again. 

With 1 in 7 couples struggling with infertility, we believe that opening the conversation around the topic is incredibly important, to not only help support those within the community but also spread awareness and educate others. Before we discuss the physical factors that can cause infertility, please know that if you need support on your path to parenthood, we are always here to guide you.

How lack of ovulation causes infertility  

Anovulation, also known as the inability to ovulate, is the most common cause of infertility. Ovulation is the process in which a mature egg is released from the ovary, and travels down the fallopian tube, where it prepares to be fertilised by the sperm. When trying to conceive, it is a crucial event, as it presents you with your “fertile window” – the 5-6 days in which you can get pregnant. 

Research suggests that as many as 25% of infertility cases are caused by anovulation, which can be explained by the following reasons:

  1. Gynaecological or ovarian complications: such as Polycystic Ovary Syndrome (PCOS) or Primary Ovarian Insufficiency (POI). (We’ll explore these in further detail below)
  2. Age: As you age your ovarian reserve declines as does the quality of your eggs.
  3. Endocrine disorders: Certain conditions that affect your reproductive hormones in your body such as, thyroid disease or defects in the hypothalamus, can also affect the hormones that trigger ovulation.
  4. Lifestyle and environmental factors: such as smoking, an unhealthy diet, consuming excess alcohol and/or drugs and more.
  5. Problems in the Menstrual Cycle

Another possible explanation that is linked to failure to ovulate, is a problem with the egg maturation process. This means that an “immature” egg may be released from your ovaries when it is not quite ready. In this case, it may be unable to travel down the fallopian tubes to be fertilised.


Polycystic ovary syndrome (PCOS), is the most common hormonal condition, affecting as many as 1 in 10 people with ovaries. It is also considered one of the main causes of infertility. People with PCOS produce higher levels of androgens, which are considered “male” hormones. These androgens can then interfere and disrupt your menstrual cycle and ovulation.

Although not present in all, some people with PCOS also possess tiny fluid-filled sacs, called cysts in their ovaries. These can sometimes block the release of an egg from your ovaries. As PCOS is still under-researched and misunderstood, many people are left undiagnosed and are unaware they have it until they are actively trying to conceive. If you would like to understand more about PCOS click here.


Primary ovarian insufficiency (POI), explains when the ovaries stop working “normally” before the age of 40. Due to the ovaries being responsible for producing the core hormones needed to work a regular menstrual cycle when their function is disrupted ovulation either does not occur regularly or stops completely. People with POI also often have a lower ovarian reserve, meaning fewer eggs for their age. Without a sufficient amount of eggs and the correct level of hormones needed to regulate your cycle, the possibility of conceiving is reduced considerably. According to the National Infertility Association, POI can be caused by genetics or autoimmune factors and is much less common than PCOS, affecting only 1 in 100 women younger than 40. Understand more about POI here.

Structural Infertility Causes

When thinking about your reproductive health organs, there are many different components to consider. And they all play vital roles in your fertility and general health. These organs include your ovaries, fallopian tubes and uterus. One other possible cause of infertility is explained by either a physical dysfunction or a problem in the growth or structure of these organs, disabling them to function effectively. 

These organs all play vital roles throughout the menstrual cycle, such as your egg being released from your ovaries, and travelling through your fallopian tubes to the uterus, where it awaits fertilisation – and if this occurs – is implanted. If there is any structural damage to your fallopian tubes, it can cause blockages, which can prevent the egg and sperm from meeting for the fertilisation process. 

Additionally, if the structure of your uterus is abnormal, this can also cause infertility problems, as it may prevent the implantation process needed to create a healthy embryo and pregnancy. Other possible explanations of implantation failure are:

  1. Defects in the embryo are either genetic or simply embryonic
  2. Endometrium Defects: A defect in the wall of your uterus
  3. Endometriosis
  4. Hormone resistance, in particular, progesterone.
  5. Scar tissue in the endometrium.

Structural infertility problems can also be explained by scarring of the uterus, which can increase the risk of pregnancy loss. This scarring can be caused by several factors, such as surgery, infections, or possible previous injuries. Others experience the growth of noncancerous tissues such as uterine polyps, that grow on the lining of the uterus. Polyps occur when additional tissue grows on your uterus. However, sometimes tissue grows elsewhere in your reproductive system potentially blocking your fallopian tubes and preventing pregnancy. 

Uterine Fibroids

Not too dissimilar from polyps, uterine fibroids are noncancerous tumours that affect as many as 25% of people with a uterus. They can cause symptoms such as heavy periods, intermenstrual bleeding, and pelvic pain. In some cases, depending on the location in which they grow, and whether they affect the shape of the uterus or cervix, fibroids can also cause infertility. They can also block the fallopian tubes interfering with the fertilisation and implantation process. Despite being less common than other causes of infertility, around 5-10% of infertile women and gender diverse people assigned female at birth are found to have uterine fibroids.


Endometriosis is a common reproductive health condition that affects around 1 in 10 women and people assigned female at birth, in which tissue that is similar to the lining of the womb starts to grow in other places, such as the ovaries and the fallopian tubes. This can also cause a number of life-altering symptoms, such as painful and heavy periods, pain during or after intercourse and pelvic pain. It is also another common cause of infertility, with research suggesting it is present in around 20-50% of infertility cases. The exact link between endometriosis and infertility is unknown. However, there are some theories that suggest that the tissue can also cause structural problems of the reproductive organs and also cause chemical changes in the lining of the uterus. 

Infections & Auto-immune disorders 

We are expected to contract a number of infections throughout our lives, and they can be present in any of the systems that help our body to survive. However, when considering your reproductive health system and infections, any untreated sexually transmitted infections may have serious consequences for your fertility. Infections such as chlamydia or gonorrhoea can cause scarring and blocking of your fallopian tubes. Additionally, if syphilis is left to develop, it can also cause stillbirth. There are also other forms of infections of the cervix with human papillomavirus (HPV) that could possibly cause infertility.

Dealing with Infertility

Experiencing infertility can be extremely challenging and can understandably take its toll on your mental wellbeing. Understanding your own body can help to equip you with the knowledge you need to make the right decisions for your health. At Hertility, we’re here to get you the answers you deserve and support you throughout your journey with our trusted experts. If you are struggling, please reach out to us – we’re always here to help.

Trusted Resources




Meeladah Ghani BSc (hons), MSc

Meeladah Ghani BSc (hons), MSc

Meeladah is a Ph.D. Research Student at University College London (UCL), studying her Doctoral degree with the EGA Institute of Women’s Health. Her research is focused on investigating Translational Ovarian Physiology and Pathophysiology. More specifically, the various implications of PCOS. Meeladah also has a Bachelor and Master in Experimental Pharmacology & Therapeutics, during which she was awarded the Royal Society of Biology award for her research study, which was awarded in the Houses of Parliament, on novel medications used to treat PCOS.

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