Polycystic Ovarian Syndrome.
Read about it, if interested.
It is one cause of infertility in women but not something which causes absolute infertility. Meaning, it can be treated in some cases and pregnancy can occur. Also, women with this condition may not know if they cannot conceive. They may have irregular periods though.
The man I talked about unfortunately had absolute infertility. He had “Undecended testes”. Meaning his testes never came down to where they belong, since his birth. He should have known this prior to marrying.