A woman may not realise that she is pregnant, and an abnormal bleed may be caused by a very early miscarriage. Up to 15% of all pregnancies end as a miscarriage, usually because of some abnormality in the developing foetus or placenta.
During the menopause, instead of cycling smoothly and evenly through the monthly changes, sex hormone levels start to change suddenly and inappropriately. This causes irregular menstrual periods, hot flushes, headaches, irritability, personality changes, breast tenderness, tiredness and pelvic discomfort. Postmenopausal bleeding (PMB) is a particular sinister sign and requires immediate investigation.
Taking the oral contraceptive pill will normally regulate the menstrual cycle very effectively, but if a pill is missed, or fails to work because of vomiting, diarrhoea or interaction with other medications (e.g. antibiotics), the sudden change in hormone levels may cause an irregular bleed. A similar effect can occur when taking hormone replacement therapy after the menopause.
Endometriosis is a sinister disease which is due to cells that normally line the inside of the uterus becoming displaced, and moving through the Fallopian tubes to settle around the ovary, in the tubes themselves, or on other organs in the belly. In these abnormal positions they proliferate, and when a menstrual period occurs, they bleed as though they were still in the uterus. This results in pain, adhesions, damage to the organs they are attached to, and infertility.
A psychological stress (e.g. death in family, losing job) may affect a woman’s pituitary gland under the brain and thus her sex hormone levels so that her menstrual periods stop or become frequent and irregular.
Other uterine causes of abnormal vaginal bleeding include:
- fibroids (balls of scar tissue in the muscular wall of the uterus),
- pelvic inflammatory disease,
- ectopic pregnancy (pregnancy outside the uterus),
- a prolapsed uterus (uterus slips down into vagina),
- irritation of the uterus after an abortion,
- a hydatidiform mole (an overdeveloped cystic placenta),
- polyps, tumours or cancer of the uterus (endometrial carcinoma).
Vaginal causes include:
- an infection of the vagina (vaginitis),
- ulceration and bleeding from the wall of the vagina,
- ulcerated or cancerous cervix or vagina,
- an injury to the vagina from over enthusiastic sex,
- using mechanical sex aids,
- a fall astride a bar.
Ovarian causes include mittelschmerz (slight blood loss and pain at the time of ovulation), and tumours, cysts or cancer of the ovary.
Any disease that slows the rate at which blood clots, and drugs used to slow blood clotting (e.g. warfarin) may cause abnormal vaginal bleeding if the dose is too high.