From a conventional medical perspective, the main categories of female subfertility include:

1. Ovulation and cycle disorders ~

Ovulation problems are one of the most common causes of subfertility in women. They may include:

• Polycystic ovary syndrome (PCOS) – characterised by irregular or absent ovulation, elevated androgens, multiple follicles on ultrasound, and often insulin resistance. 
• Functional hypothalamic amenorrhoea – where stress, under‑eating, excessive exercise or low body weight suppress the hormonal signals that trigger ovulation.  
• Thyroid disorders – both underactive (hypothyroidism) and overactive (hyperthyroidism) thyroid can disrupt cycles and ovulation.  
• Hyperprolactinaemia – elevated prolactin can interfere with ovulation and luteal function.  
• Luteal phase problems – insufficient progesterone production or too short a luteal phase may impair implantation.
• These disturbances can lead to irregular cycles, absent periods, anovulation or subtle problems with egg maturation and endometrial development.

2. Tubal and pelvic pathology ~

The fallopian tubes play a crucial role: they pick up the egg, provide the environment for fertilisation and transport the embryo to the uterus. If the tubes are damaged, blocked or surrounded by adhesions, this can significantly reduce the chance of pregnancy.

Important causes are:  

• Pelvic inflammatory disease (PID) – often following sexually transmitted infections such as chlamydia, sometimes with few or no symptoms at the time.  
• Endometriosis – where endometrial‑like tissue grows outside the uterus, potentially causing inflammation, adhesions and distorted pelvic anatomy.  
• Previous abdominal or pelvic surgery– which can lead to adhesions and altered tube mobility.  

Tubal pathology not only reduces the chance of conception but also increases the risk of ectopic (tubal) pregnancy.

3. Uterine and cervical factors ~

Structural or functional uterine factors can affect both implantation and the ability to carry a pregnancy:

• Congenital uterine anomalies (such as a septate uterus, bicornuate uterus or double uterus).  
• Fibroids (myomas) that distort the cavity or interfere with blood flow.  
• Severe endometrial pathology or scarring (Asherman’s syndrome).  

Cervical factors, such as very unfavourable cervical mucus or problems with the interaction between sperm and mucus, can also play a role in some couples.

4. Lifestyle, comorbidities and other factors ~

A range of broader health and lifestyle factors can influence female fertility, for example:

• Smoking, alcohol and drugs – associated with lower fertility and higher miscarriage risk.  
• Body weight – both underweight and overweight can disrupt hormonal balance, ovulation and implantation.  
• Metabolic issues – such as insulin resistance, diabetes and metabolic syndrome.  
• Autoimmune and systemic diseases – like autoimmune thyroid disease or rheumatological conditions.  
• Occupational and environmental exposures – contact with certain chemicals, heavy metals or endocrine‑disrupting substances.  

These factors often interact with each other and with more specific gynaecological causes.

5. Unexplained subfertility ~

In roughly 30% of couples, all standard tests (for both partners) are within reference ranges, yet pregnancy does not occur. In that case, the fertility clinic may speak of ‘unexplained subfertility’.

This does not mean there is no cause, but that current routine tests cannot detect it. Often there are more subtle issues in hormone regulation, egg quality, endometrial receptivity, immune balance, microbiome or systemic health.