Infertility: classification, causes, history and investigations

1. Big picture

Infertility is a couple-based diagnosis, not only a female diagnosis. In the exam, start with this logic:

Infertility
        ↓
Evaluate both partners together
        ↓
Is ovulation occurring?
        ↓
Are sperm adequate?
        ↓
Are tubes patent?
        ↓
Is the uterus/cervix suitable for implantation and pregnancy?
        ↓
If all normal → unexplained infertility

The examiner wants you to show a structured diagnostic approach:

1. Define infertility correctly.
2. Classify it: primary/secondary; male/female/mixed/unexplained.
3. Take a targeted history from both partners.
4. Investigate the four essential fertility requirements: