Factors that can have an impact on female fertility include:

Trouble releasing eggs, called ovulating, or trouble with regular periods. Hormone-related conditions can affect the release of eggs from the ovaries. These conditions include polycystic ovary syndrome, high prolactin hormone levels and thyroid conditions. Other conditions that may change ovulation or periods are poorly controlled diabetes and some autoimmune diseases such as lupus.
Uterine or cervical conditions. This includes growths in the uterus, such as polyps or fibroids.
Fallopian tube damage or blockage. This can be in one or both tubes through which eggs travel from the ovaries to the uterus. These tubes are the fallopian tubes. Often the cause is pelvic inflammatory disease.
Having the tissue that lines the inside of the uterus grow outside the uterus. This is called endometriosis.
Early menopause, also called primary ovarian insufficiency. This happens when the ovaries stop working and periods stop before age 40.
Bands of scar tissue that bind organs together. These bands are called pelvic or uterine adhesions. They can happen after a pelvic infection, appendicitis, or abdominal or pelvic surgery.
Aging. Waiting to try to get pregnant can lower the chance of being able to conceive. As you move closer to your 40s, you lose eggs at a faster rate. And the eggs you have are less likely to become fertile.