From the Research
It typically takes 2-3 years after menarche for most adolescents to establish regular menstrual cycles. During this initial period, irregular cycles are common and considered normal as the hypothalamic-pituitary-ovarian axis matures. The most recent and highest quality study, published in 2019 1, demonstrates that healthy post-menarchal adolescent girls show multi-level reproductive axis immaturity, which contributes to menstrual irregularity. This study found that adolescents had anovulatory cycles, ovulatory cycles with a short luteal phase, or ovulatory cycles with a normal luteal phase, without differences in cycle length, chronologic or gynecologic age, or BMI.
Some key points to consider:
- In the first year after menarche, cycle lengths can vary widely, ranging from 21-45 days, with bleeding lasting 2-7 days.
- By the third year post-menarche, about 60-80% of adolescents will have established regular cycles, typically settling into a pattern of 21-35 days between periods.
- This irregularity occurs because early menstrual cycles are often anovulatory, as the body's hormonal feedback systems are still developing.
- Parents and adolescents should understand that this irregularity is a normal part of development and not necessarily cause for concern.
- However, if an adolescent experiences consistently very heavy bleeding, severe pain, cycles shorter than 21 days or longer than 45 days that persist beyond 2-3 years after menarche, or if periods stop for more than 3 months once they've been established, medical evaluation is recommended, as suggested by studies such as 2 and 3.
It's essential to note that while the 2019 study 1 provides the most recent and highest quality evidence, other studies, such as those published in 2018 4 and 2012 5, also support the idea that menstrual irregularity is common in the first few years after menarche. However, the 2019 study offers the most comprehensive and up-to-date understanding of the reproductive axis immaturity in adolescents.