From the Guidelines
The average age for the onset of menses is approximately 12 years old, as reported in a recent study published in 2018 [@25@].
Factors Influencing Menarche
The onset of menarche is influenced by various factors including genetics, body weight, nutrition, and overall health status.
- Genetic factors play a significant role, with daughters often experiencing menarche at similar ages as their mothers.
- Body weight and nutrition are also important, as girls with higher body fat percentages tend to start menstruation earlier due to the contribution of adipose tissue to estrogen production.
- There has been a gradual decrease in the average age of menarche over the past century, likely due to improved nutrition and health conditions, as observed in studies such as [@25@].
Clinical Considerations
If a girl hasn't started menstruating by age 15 (primary amenorrhea), or if menstruation begins before age 8 in girls, medical evaluation is recommended as these situations may indicate underlying health concerns.
- Early or late onset of menarche can be associated with various health issues, and timely medical evaluation can help identify and manage these conditions.
- Studies such as 2 highlight the importance of considering environmental and chemical exposures in the context of reproductive health and development.
Recommendations
Based on the most recent and highest quality evidence, it is essential to monitor girls' development and seek medical attention if menarche occurs outside the typical age range [@25@].
- Healthcare providers should be aware of the factors influencing menarche and the potential health implications of early or late onset.
- Further research is needed to fully understand the effects of environmental and chemical exposures on reproductive development, as suggested by studies such as [@14@] and [@17@].
From the Research
Average Age for Onset of Menses
- The average age for the onset of menses, also known as menarche, has varied throughout history and across different populations 5.
- In prehistoric times, menarche is believed to have occurred between 7 and 13 years of age, while in classical and medieval times, it occurred at around 14 years of age 5.
- In the 20th century, the age at menarche decreased significantly in industrialized countries, occurring at around 12-13 years of age, due to improvements in socioeconomic conditions 5.
- A more recent study found that the average age of menarche in a group of transgender male and gender nonbinary adolescents was 15 years (SD 1.6) years 6.
- However, it's worth noting that the age at menarche can vary widely among individuals and is influenced by a combination of genetic and environmental factors 5, 7.
Factors Influencing Menarche
- Hormonal changes play a crucial role in the onset of menarche, with the hypothalamic-pituitary-ovarian axis regulating the menstrual cycle 7.
- Gonadotropin-releasing hormone (GnRH) secretion increases at the onset of puberty, stimulating follicle-stimulating hormone (FSH) and luteinizing hormone (LH) production, which in turn regulate estrogen production in the ovaries 7.
- Other factors, such as primary ovarian insufficiency, can also impact the age at menarche and menstrual regularity 8.