During a normal ovulatory cycle, a single ovum is released from the ovaries. If fertilisation does not occur the ovum is removed as part of the menstrual bleed (period). The body will also expel some of the thickened endometrial wall that develops each month in preparation for implantation of a fertilised egg.
The complication is that menstrual cycles vary in length and anything from 21 to 35 days is considered normal. A period, when present, will usually occur 10-14 days after ovulation.
Abnormal uterine bleeding
If bleeding occurs at a different time it is considered to be abnormal uterine bleeding. When the bleeding is not part of the normal menses and/or starts before day 20 of the menstrual cycle, it is considered to be intermenstrual bleeding. Studies have suggested that between 14 and 17% of women have bleeding between periods.
What causes intermenstrual bleeding?
The first thing to consider is whether age may be contributing.
Irregular periods are very common in girls who have only just started their periods. In fact, it can take up to six years for the menstrual cycle to become regular. Thus, whilst it is worth monitoring dates and timings, irregularities in menstruation in females of this age are rarely anything to be concerned about.
Abnormal cycles are also frequently seen in women who are approaching the menopause. The years that precede the menopause are known as the perimenopause. It is during these years that ovulation starts to slow down and menstruation becomes irregular, then sporadic, before ceasing altogether.
It is also important to establish the type of bleeding; whether it is heavy and period-like, or spotting. Spotting is light, there will not be enough to fill a tampon or pad, and the blood will usually be dark red or brown. It can happen during pregnancy (particularly in the early stages when the fertilised egg first implants) and as a side effect to hormonal birth control. Spotting is not usually anything to worry about and can simply be an indication that not all of the endometrial tissue was removed during menstruation. Monitor any spotting and if it is consistent and becoming heavier see your doctor.
Heavy bleeding between periods can be caused by structural abnormalities, such as polyps and fibroids; or hormonal imbalances causing ovulatory dysfunction. If you are experiencing heavy intermenstrual bleeding your doctor may want to check your progesterone levels across your cycle to identify whether you have an endocrine disorder.
Another cause of intermenstrual bleeding is infection. Vaginal bleeding can be a symptom of an infection of the reproductive tract. Often the body is able to clear infections without the need for medical intervention; but you should still consult a doctor for confirmation and to ensure that there will be no lasting negative effects. In severe cases, infection-induced scarring of the reproductive organs can result in difficulties in conceiving.
The health risks of intermenstrual bleeding
One of the main health risks of heavy bleeding between periods is anaemia. The symptoms of anaemia are fatigue, headaches, dizziness and an irregular heartbeat. It can be treated with iron supplements.
You may also wonder whether frequent episodes of intermenstrual bleeding will have an effect on fertility. This will largely depend on the reason for the bleeding. If fluctuating hormone levels are responsible, you may experience difficulty conceiving because your hormones need to be present at exactly the right levels for ovulation to occur. Likewise, structural barriers can impede fertilisation. If the bleeding occurs as a single episode, you are unlikely to fall pregnant that cycle, but may find that your fertility is actually enhanced during the cycle that follows. Subsequent cycles should not be affected. Repetitive episodes of intermenstrual bleeding probably will lower your overall chances of conceiving.
No woman should have to put up with persistent bleeding. It can be draining from a financial, physical and emotional perspective. Diagnosis may have to be made via a process of elimination, but it is essential that doctors consider all eventualities and perform the necessary tests, so that the right treatment can be instigated.
Nabta is reshaping women’s healthcare. We support women with their personal health journeys, from everyday wellbeing to the uniquely female experiences of fertility, pregnancy, and menopause.
Get in touch if you have any questions about this article or any aspect of women’s health. We’re here for you.
- “Abnormal Uterine Bleeding (Booklet).” ReproductiveFacts.org, The American Society for Reproductive Medicine, www.reproductivefacts.org/news-and-publications/patient-fact-sheets-and-booklets/documents/fact-sheets-and-info-booklets/abnormal-uterine-bleeding/. Revised 2012.
- Crawford, Natalie M., et al. “Prospective Evaluation of the Impact of Intermenstrual Bleeding on Natural Fertility.” Fertility and Sterility, vol. 105, no. 5, May 2016, pp. 1294–1300., doi:10.1016/j.fertnstert.2016.01.015.
- Shapley, M, et al. “An Epidemiological Survey of Symptoms of Menstrual Loss in the Community.” The British Journal of General Practice, vol. 54, no. 502, May 2004, pp. 359–363.
- “Vaginitis.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 13 Nov. 2019, www.mayoclinic.org/diseases-conditions/vaginitis/symptoms-causes/syc-20354707.
- Whitaker, L, and H O D Critchley. “Abnormal Uterine Bleeding.” Best Practice & Research. Clinical Obstetrics and Gynaecology, vol. 34, July 2016, pp. 54–65., doi:10.1016/j.bpobgyn.2015.11.012.