Pre-teen girls typically begin their menstruation cycle, or period, at 12 years old. In the first two to three years, period cycles may take a while to establish monthly regularity, resulting in irregular periods. Beyond that two-to-three-year mark, irregular periods can indicate a health issue.   

Arkansas Children’s has the only two fellowship-trained pediatric and adolescent gynecologists in the state, including Kathryn C. Stambough, M.D., service chief for the Arkansas Children’s Hospital pediatric and adolescent gynecology clinic in Little Rock. She is also an assistant professor in the division of pediatric and adolescent gynecology in the department of obstetrics and gynecology at the University of Arkansas for Medical Sciences.   

"What sets us apart is we went through extensive formal training in obstetrics and gynecology and then did additional training to tailor that care to the reproductive needs of children and teens. It is rare to have this extra training in a general OBGYN setting," Stambough said. "Children and teenagers are not just little adults. We are thoughtful about the reproductive needs of our pediatric patient population."  

Even if they have not started their period cycles, girls between 13 and 15 should make an appointment with a gynecologist. Stambough said this allows young patients to receive crucial medical guidance, ensuring there are no concerns as they go through puberty and explaining normal parameters about what to expect from their first period and future cycles.   

After two to three years following their first cycle, a person should have a minimum of eight periods a year. It is normal to occasionally miss a cycle or have a longer time in between periods due to stress, nutrition, exercise and illness. 
 
However, for example, having three months or more in between cycles indicates an irregular period. About 20 to 25% of daily appointments at the ACH gynecology clinic handle patient concerns regarding irregular periods.  

Stambough shared the following five questions parents should ask regarding irregular periods: 

1. What is an irregular period?   

A period occurring more frequently or less frequently than a typical monthly cycle.   

The definition varies depending on the age of the patient. In the first two to three years of an adolescent patient starting their period, there will be some irregularity as the body establishes monthly periods.  

Anywhere from 21 to 45 days between cycles is considered normal in the early years. 

Anything more than three months between cycles or more frequently than 21 days between cycles would be considered an irregular period, even within the first three years of a child starting their period.  

As patients age, periods typically become more consistent, roughly 21 to 35 days between cycles. Once a regular monthly period is established, it would not suddenly become irregular without an underlying cause.   

2. What’s the most common reason that periods are irregular?   

The most common reason a period might be irregular in the first two to three years after periods start is hypothalamic pituitary ovarian (HPO) axis immaturity. This means the body is still sorting out the coordinated signaling every month from the brain to the ovaries to the uterus to have a set period cycle.   

As patients get older and pass the age for HPO axis immaturity, other common causes include thyroid disease and polycystic ovarian syndrome (PCOS), which occurs in about one in 10 patients. These causes require treatment.   

Because the symptoms of PCOS can overlap with puberty, including increased hormones, excess hair and acne, parents often worry their child's period irregularity might indicate PCOS. However, this is not always the case. Gynecologists recommend giving a child's period time to become regular in at least the first two to three years before making a PCOS diagnosis.    

3. What evaluation would a patient have for an irregular period?   

When a patient comes to the ACH gynecology clinic with an irregular cycle, the first thing our medical experts do is document the patient’s period history, asking: 

  • When the first period started
  • Frequency of periods over time   
  • How long their period usually lasts  
  • Amount of menstruation products a patient uses each day of their period  
  • Any other symptoms associated with their cycle   


A pelvic exam or ultrasound is not typically required to evaluate an irregular period cycle in a pediatric or adolescent patient. If the questionnaire indicates HPO axis immaturity, gynecologists may recommend using a menstrual calendar to see if the cycle regulates over time.   

Bloodwork may be drawn to test for causes of irregularity, like thyroid disease, if a patient’s period has been irregular for a significant amount of time. 

4. Why take irregular periods seriously?    

When patients go significant amounts of time without a cycle and eventually get their period, it can be heavier or longer than a regular menstrual cycle. As patients get older, if they continue to have prolonged episodes of no periods, it can impact their uterine health.   

5. What is the treatment for irregular periods?   

Treatments for irregular periods vary. It may include a menstrual calendar and observation, a short course of medication or hormonal therapies to regulate a cycle.   

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