IVF Babble
What causes infertility?
Infertility is a delicate and challenging subject. If you're struggling to conceive, the grief, shame, anger, and frustration can start to consume your entire life. Knowing the causes of your infertility can help you make informed decisions about your treatment options.

It can be hard to find reliable information on the internet – there’s tons of conflicting information out there. But there are some things you should know if you’re trying to have a baby – especially if you are in your late 30s or 40s and are having trouble conceiving. That’s why we’ve compiled this guide to help you understand the most common causes of infertility.

The causes of infertility are often broken down into three categories: male-factor fertility problems (e.g., low sperm count or poor motility), female-factor fertility problems (e.g., endometriosis, PCOS, and fibroids), and unexplained infertility. The cause of infertility may vary from person to person and couple to couple, but there are some common causes that we’ll talk about now.

Common causes of infertility in women

There are many different conditions and factors that can cause infertility in women and AFAB (assigned female at birth) people.

Polycystic Ovarian Syndrome (PCOS)

Polycystic Ovarian Syndrome (PCOS) describes a set of symptoms in women that are related to elevated androgens. It can cause fertility problems and other complications, such as weight gain, excessive hair growth, baldness, or very long periods.

The term ‘polycystic’ means that the ovaries become enlarged due to fluid-filled sacs, called follicles or “follicular cysts” (despite not being cysts). These sacs produce hormones, including oestrogen and testosterone, but usually more androgen (a male sex hormone) than usual. This excess androgen production disturbs your menstrual cycle, making it difficult for your ovaries to release eggs each month.

Thankfully, PCOS can often be treated with hormone therapy and/or medication. Weight loss can also help to improve PCOS symptoms, as can a healthy diet and getting plenty of exercise.

Thyroid Problems

Thyroid problems are one of the leading causes of infertility. Having an overactive or underactive thyroid gland can prevent ovulation, making it harder to get pregnant. However, not every woman with thyroid problems will have infertility issues.

That said, if you are trying to get pregnant and facing difficulty, your doctor may run tests on both your pituitary gland and your thyroid levels.

The body’s two main types of thyroid hormone are triiodothyronine (T-three) and thyroxine (T-four). If you produce too much or too little of either one, you can experience weight gain or loss, increased intolerance to cold, constipation, fatigue, trouble sleeping, pain in your joints, and hair loss. In most cases, thyroid problems can be treated with medications – speak to your GP and fertility specialist.


Endometriosis occurs when the cells from the lining (endometrium) of your uterus (womb) grow in other parts of the body. For example, they can grow on your ovaries or fallopian tubes, and in your stomach, liver, kidneys and even brain. This can cause pain and fertility problems, especially if the growths are inside or attached to your ovaries.

Endometriosis can be treated with hormone therapy drugs such as gonadotropin-releasing hormone (GnRH) analogues that lower oestrogen levels, contraceptive pills that contain progesterone, or surgery to remove the excess tissue

Uterine Fibroids

Fibroids are non-cancerous tumours that grow from the smooth muscle cells of the uterus. Though they are more common in women who have gone through menopause, they can also occur in younger women. They can cause pain and menstrual problems, including heavy periods, infertility, and recurrent miscarriage.

Treatments for uterine fibroids include hormone therapy and/or surgery to remove the fibroids.


Adenomyosis is a condition where the tissue that usually lines your womb (endometrium) grows into your uterine muscle. This can cause painful periods and make it harder to get pregnant.

Treatment options for adenomyosis include hormone therapy or surgery to remove the tissue that is causing pain, depending on what symptoms you have. If your condition has caused abnormal bleeding, other treatments may also be needed (like a hysterectomy). That said, there are currently no formal recommendations about treating adenomyosis to increase the chance of conception. So, it’s important to speak to your fertility specialist.

Uterine Malformations

Uterine malformations, such as a bicornuate uterus or Asherman’s Syndrome, can be congenital (something you are born with) or can be acquired. They can make it very difficult to get and stay pregnant.

A bicornuate or septate uterus is a congenital condition that causes a physical division in your womb. This can make it difficult for you to conceive naturally and can cause miscarriage if you do get pregnant. Asherman’s Syndrome, on the other hand, occurs where there are scars inside your uterus, which can cause it to become rigid. This can also make getting pregnant difficult and increase the risk of miscarriage if you do conceive. Surgery is the only treatment for uterine malformations – speak to your doctor and fertility specialist.

Premature Ovarian Insufficiency

Premature Ovarian Insufficiency (also known as Preterm Ovarian Failure) occurs when a woman experiences menopause before the age of 40. It can cause infertility and other health issues, such as osteoporosis. Premature Ovarian Failure is often caused by a medical condition, such as chemotherapy. It can also be the result of genetic abnormalities or autoimmune disease that attacks healthy ovarian tissue.

Symptoms of Premature Ovarian Failure include menstrual irregularities, such as heavy periods, irregular bleeding, and the absence of menstruation, hot flushes, and vaginal dryness.

If you start experiencing symptoms of Premature Ovarian Failure, it’s crucial that you speak with your doctor immediately and start looking into possible causes. You might also wish to take measures to protect their fertility, such as freezing your eggs.

Pelvic Inflammatory Disease

Pelvic Inflammatory Disease (PID) is an infection that can affect your reproductive organs, especially your fallopian tubes. Symptoms of PID include abdominal pain and tenderness, fever, unusual vaginal discharge with a foul odour, or menstrual bleeding between periods.

The symptoms can be mild to severe in some cases and may last from a few days to a few months. PID can cause infertility in severe cases or even lead to life-threatening complications, such as sepsis and ectopic pregnancy.

PID is usually caused by an untreated sexually transmitted infection (STI), like chlamydia or gonorrhoea. In many cases, it can be treated with medications, and your fertility can be fully restored. However, if left untreated, it can cause a build-up of scar tissue that makes it difficult or impossible for an egg to travel down your fallopian tubes.

Cervical Mucous Problems

Your cervical mucous is meant to get thinner when you ovulate, allowing sperm to swim easily through your vaginal canal and fallopian tubes to reach the egg. However, if your cervical mucous is too thick or too acidic, it can be difficult for the sperm to find its way. Minor problems will often resolve themselves, but more severe problems can require hormonal medication or fertility treatments to overcome.

Common causes of infertility in men

Here are some of the most common causes of infertility in men and other AMAB (assigned male at birth) people.

Low Sperm Count

Low sperm count is one of the most common causes of infertility in men. The average number for normal fertility levels ranges from 20 million/ml-120million/mL. If your numbers fall below this range, you may have issues with being able to conceive naturally. Low sperm count is often caused by a varicocele, exposure to toxins, like pesticides and heavy metals, STIs, such as gonorrhoea or chlamydia, and testicular trauma.

Poor Motility

Poor sperm motility is also a common cause of infertility in men. Healthy sperm move quickly and with purpose, but poor motility means that it takes more energy for the cells to travel, which often leads them to get stuck or lost along their journey. This can be caused by an infection like chlamydia or gonorrhoea, as well as issues such as varicoceles and testicular trauma and low sperm count.

Issues with Sperm Shape (Morphology)

Sperm shape (morphology) is another common cause of infertility in men. The head should be oval-shaped so that it can effectively piece the outer membrane of the egg. However, if the cell has two tails or is too rounded, it cannot effectively fertilise the egg. Poor sperm morphology is caused by increased testicular temperature, toxic chemical exposure, STIs, and genetic traits.

Varicocele and Testicular Abnormalities

A varicocele is an abnormal enlargement of the veins in the spermatic cord. It is a common cause of infertility and can be treated with surgery. However, it is important to find out what’s causing your varicocele before you seek surgical options. some of the most common causes of varicocele include injury to the scrotum, failure of the valves in the veins, and abnormal blood flow.

Varicoceles can lead to male infertility if left untreated. This is especially true for those with a varicocele on both sides, as this could cause damage to more than half of your sperm-producing capacity.


Hypogonadism occurs when the testes do not produce enough testosterone, causing low semen volume and poor sperm production. The condition can be caused by genetic issues, radiation exposure, or an autoimmune disease that turns off your body’s natural ability to produce testosterone.

You can treat hypogonadism by taking exogenous testosterone, but it may be possible to treat the condition without pharmaceutical aids. Speak to your GP or a specialist about your options.

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