During a normal ovulatory cycle, a single egg (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. The only thing that is consistent is that a period will always occur 10-14 days after ovulation.
If bleeding occurs at a different time it is considered to be abnormal uterine bleeding. Studies have suggested that 25% of women of reproductive age experience abnormal uterine bleeding and between 14 and 17% have bleeding between periods.
The first thing to consider is whether age may be contributing.
In girls who have only just started their periods, irregular bleeding is very common. 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. There are health implications to going through the menopause, particularly for those women who experience an early menopause, as oestrogen levels drop and normally this hormone plays a critical protective role against osteoporosis, breast cancer and heart disease. Thus, whilst irregular periods might be an inevitable sign of aging, the full health implications of the menopause should not be trivialised.
It is also important to establish whether the bleeding 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. Heavy, persistent bleeding during pregnancy is a sign of miscarriage and should always be checked by a doctor.
Heavy bleeding between periods can be caused by structural anomalies, such as fibroids; ovulatory dysfunction; or medical conditions, such as hypothyroidism. Click here for a comprehensive review on how these conditions, and others, cause abnormal uterine bleeding.
One health risk of heavy bleeding between periods is anaemia, which is a consequence of not having sufficient iron in the blood. The symptoms of anaemia are fatigue, headaches, dizziness and an irregular heartbeat. It can be treated with iron supplements.
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.
- Shapley, M, et al. “An Epidemiological Survey of Symptoms of Menstrual Loss in the Community.” The British Journal of Genera Practice, vol. 54, no. 502, May 2004, pp. 359–363.
- 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.
- “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.
- Purdie, J. “What Causes Two Periods in One Month?” Healthline, www.healthline.com/health/womens-health/two-periods-in-one-month. Medically reviewed by Debra Sullivan, PhD, MSN, RN, CNE, COI on January 15, 2019.