(IMB) Bleeding between periods that are otherwise regular. If it happens while on the oral contraceptive pill it's called breakthrough bleeding; if it happens over a few days before a period starts properly it's premenstrual spotting; if it happens after sex it's postcoital bleeding. These forms of IMB have different, usually important, causes. The formal term for it is metrorrhagia.

Inflammation of the cervix, usually because of infection. Sperm might or might not have trouble getting through the cervical mucus: this can be tested with a postcoital test. Occasionally cervicitis can mean that there is endometritis and salpingitis, in which case there will usually be pus present in the cervix. A cause of intermenstrual bleeding and postcoital bleeding. Clinically there might be contact bleeding when taking a PAP smear.

A polyp of the endometrium (lining of the uterus), sometimes without symptoms, sometimes with abnormal bleeding such as intermenstrual bleeding, premenstrual spotting or heavy periods. A cause of infertility (and of failure of assisted conception to result in pregnancy). Diagnosable with transvaginal ultrasound.

Traditional medical term for intermenstrual bleeding.

A form of light intermenstrual bleeding consistently timed over a few days to a week before the period starts properly, although it might not happen every month. About 80 percent of the time it signals the presence of endometriosis, making it the most predictive symptom for this condition; about 10 percent of the time it means an abnormality of the uterus such as fibroids, an endometrial polyp or endometritis; the remaining 10 percent of the time there is no explanation found. It has nothing to do with premenstrual tension, which if present is a coincidence.

A fibroid (or myoma) that grows from the wall of the uterus inwards to distort the endometrial cavity. Can be a cause of menorrhagia (heavy periods), intermenstrual bleeding, premenstrual spotting, infertility and miscarriage.