Most girls get their first period around the age of 12; this is usually about two years after the first signs of puberty. The medical name for starting your periods is menarche. Whilst 12 is the average, menarche can occur in girls as young as 8 years old. Furthermore, there is evidence that, particularly in some countries, the average age of puberty is falling.
Certainly, 200 years ago it was normal for a girl to start her periods between the ages of 15 and 17. However, nowadays that is the exception, rather than the norm; and up to 98% of girls will have started their periods before their fifteenth birthday.
So should you be worried if your daughter falls into the 2% of girls who have not yet started their periods?
The answer is, probably not. Some teenagers are just ‘late bloomers’ and, as the age of puberty tends to have a familial component, if you started your periods later than many of your friends, it is likely that your daughter will experience a similar thing.
Lifestyle factors can also play a role. Being overweight or underweight can delay the start of puberty, as can excessive exercise. This is why ballerinas and gymnasts very often start their periods later than their counterparts. Having an eating disorder or suffering from intense stress can also delay menstruation. For any of these factors, resolving the underlying issue should rectify the issue; for example:
- Finding a healthy way to lose or gain weight.
- Reducing the intensity of an existing exercise schedule.
- Identifying and acting to resolve the things that are causing stress.
In some cases there will be an underlying medical issue. Some cancer treatment might delay or prevent puberty from occurring. There may be a structural problem whereby part of the reproductive system is missing or blocked; endometriosis, characterised by the build up of endometrial deposits outside of the uterus, is probably the most well known structural impediment to normal reproductive function. A congenital condition called Müllerian agenesis results in complete or partial absence of parts of the uterus and vagina.
Other genetic disorders, including Turner syndrome can delay puberty, as can problems with the hypothalamus or pituitary gland. Hypothalamic dysfunction that occurs before puberty often resolves itself over time. Another medical complication that can cause girls to fail to have regular menstrual cycles is polycystic ovary syndrome (PCOS). Research has shown that girls with clinically-diagnosed PCOS often start their periods earlier or later than average. Furthermore, PCOS regularly causes menstruation disturbances, such as irregular periods, which can be exacerbated in those who have only just been through puberty.
Any of these medical conditions will need to be diagnosed by a doctor, who will then be able to offer advice on the best way of managing the symptoms.
The age at which a girl starts her periods is influenced by a combination of genetic markers (predispositions) and environmental factors such as diet and exercise. To date, the research and clinical community has limited data on which specific genes are involved; however, with the advent of genome-wide association studies (GWAS), potential genetic targets can be identified and explored further.
More research is needed to understand the factors contributing to the timing of menstruation.
If your daughter has not had her first period by the age of 15 you may wish to consult a doctor for peace of mind, particularly if she has none of the typical signs of puberty. If, however, her breasts have started to form and she is developing pubic hair, it is very likely that her periods will start in the near future.
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- Carroll, Jessica, et al. “Environmental and Genetic Factors Influence Age at Menarche in Women with Polycystic Ovary Syndrome.” Journal of Pediatric Endocrinology and Metabolism, vol. 25, no. 5-6, 19 Apr. 2012, pp. 459–466., doi:10.1515/jpem-2012-0047.
- Karapanou, Olga, and Anastasios Papadimitriou. “Determinants of Menarche.” Reproductive Biology and Endocrinology, vol. 8, no. 1, 30 Sept. 2010, p. 115., doi:10.1186/1477-7827-8-115.
- Müller, Jørn. “Disturbance of Pubertal Development after Cancer Treatment.” Best Practice & Research Clinical Endocrinology & Metabolism, vol. 16, no. 1, Mar. 2002, pp. 91–103., doi:10.1053/beem.2002.0183.
- Practice Committee of American Society for Reproductive Medicine. “Current Evaluation of Amenorrhea.” Fertility and Sterility, vol. 90, no. 5 (suppl.), Nov. 2008, pp. S219–S225., doi:10.1016/j.fertnstert.2008.08.038.
- “Delayed Periods.” NHS, www.nhs.uk/conditions/periods/delayed-periods/.