Guest Post by Dr. Jerilynn C. Prior, UBC, Centre for Menstrual Cycle and Ovulation Research

16-year-old Jody is anxious to talk to someone. This is what she wants to say:

“My period is out of whack!  I never know when it is coming. I only get it a few times a year. . . . Is that normal?”

To answer Jody we need to ask her how old she was when her period started. In asking that we’re trying to figure out how far she is into the normal process that our cycles must go through before they are fully mature. What she describes is perfectly natural for the first year after menarche. But if her period came when she was 11 (meaning she has a gynecological age of 5), she’s experiencing something that needs careful consideration. In this post, as someone who has studied menstrual cycles for at least 30 years  and who cares deeply that all girls mature into normally menstruating and ovulating women, I’ll ask the questions that Jody might ask, and answer as honestly as the evidence allows.

Menarche is a marker of our entry into womanhood. But it is not the start of our reproductive maturation. It is rather one lone step on a reproduction growing up pathway that has been going on for several years already. If you are a mother/grandmother with a preteen child you will one day become aware that her/his sweat is now strong and smelly, like a hot and bothered adult. Or that there is longer, darker hair on his/her arms and legs. These changes are officially called “adrenarche” and are evidence that the sex-hormone-producing layers of the adrenal glands (that also make the stress hormone, cortisol, a salt-retaining hormone and sympathetic nervous system hormones epinephrine and norepinephrine) are now growing up and making male-type hormones.

“What’s a  normal age to start your period?”

Jody got her first period a few months before she turned 16. All her friends (at least those who didn’t keep it a secret) had gotten their periods long before then. Her parents had divorced when she was 12, she was upset because she was close to her dad and rarely saw him anymore.   

In well-nourished girls and young women the first period occurs between the ages of 10 and 14 with an average in North America of about 12.5 years. The average age at menarche is now a year or two younger than it was about 50 years ago, perhaps because of better nutrition and health care. If a girl is 14 and has no flow, this is normal if she is showing some breast development. Getting first flow after age 16 is not normal and is associated with later life risks for fragility fracture (breaking a bone with a fall from standing height). This is usually caused by stresses and is something from which she can totally recover called hypothalamic amenorrhea. Rarely is it something genetic or a disease but rather a protective response because of stress of several kinds—emotional/social, nutritional, illness or over-exercise, and often a combination of several.

We now know that Jody has hypothalamic delay of her menarche.

“What’s normal for cycles in the first year after your period starts?” 

I would like to tell you that we’ve carefully studied large random groups of girls through their first year after menarche from whole populations. However, that would be untrue. One Swiss physician and his wife collected information from hundreds of girls and women with some of them recording from their first flow until menopause. Here’s what they found in that first year: cycles were quite far apart (about 40-50 days on average), quite irregular and unpredictable (R. Vollman, 1997). In a random population study of about 300 teens ages 15-19 from Copenhagen County in Denmark, 77% said their cycles were regular (between 21 and 35 days apart), 22% said they were irregular, and 2 of 100 had not yet reached menarche or were experiencing amenorrhea (Munster, 1992).

“Will I ever be able to have children?”

Obviously, to become pregnant and to carry a pregnancy to a normal childbirth, requires a grown-up reproductive system. The key part of that is ovulating, releasing an egg that could be fertilized, embed into the endometrium and eventually make a placenta and the very complex blood vessel system required for a healthy baby. So what’s normal for ovulation in the first year after menarche? Susan Barr (professor of nutrition at the University of British Columbia) and I studied girls ages 9 to 11 who had not yet menstruated over two years (Barr 2001). During that time some of them got their period. When they did, we asked them to collect morning saliva one day a week and especially during the third and fourth weeks from their flow. We measured progesterone in saliva and discovered that none seemed to have ovulated until 10 months from menarche (Kalyan, 2007).

Vollman, in studying young women from after their first menstruation, found that fewer than four of any 10 cycles showed evidence of ovulation during that first year (Vollman, 1977). That rare ovulation, however, was unlikely to support a pregnancy based on a Canadian study of exercising teens ages 15-19 and averaging 2.5 years after menarche. It showed that these young women might have regular cycles and that they often ovulated, but that the luteal phase (the length of the time after ovulation until flow) was very short (Bonen 1981). It takes many days for progesterone, produced during the luteal phase, to transform the endometrial uterine lining into something secretory that supports a fertilized egg. If the adult and fertile luteal phase length is 10-16 days, as evidence suggests, these teens experienced luteal lengths of 4-8 days (Bonen, 1981) that would not be fertile.

“What’s normal for menstrual cycles in older teens like me?”

A population-based three year study of Grade 9 young women from schools to the south of Amsterdam followed more than 2,000 students  ages 14-17 at baseline with gynecological ages averaging about two years (van Hooff 2004). Sixty-two percent of these teens had regular cycles ranging in length from 22 to 41 days. [Note: the normal cycle length for adults is considered to be 21-35 days (Abraham 1978) but this teen normal range is based on Vollman]. Already at that age, 11% were on the Pill, 6% had not reached menarche, 10% had irregular cycles and 6% had oligomenorrhea (cycles 42-180 days apart). After three years, of those initially regular 87% had regular cycles, 12% had irregular cycles and two percent had oligomenorrhea (menstrual cycles farther apart than 36 days but shorter than 180 days (van Hooff 2004). Over half of those with oligomenorrhea at younger ages continued to have oligomenorrhea later (van Hooff 2004). Those with irregular cycles that were usually shorter than 35 days apart were more likely to develop regular cycles; those whose irregularity averaged 35-41 days apart were more likely to develop oligomenorrhea.

Why does having oligomenorrhea matter? Because those with oligomenorrhea were significantly more likely that women with other menstrual cycle types to develop what’s called polycystic ovary syndrome (PCOS) with unwanted face and body hair, acne and risks for obesity and diabetes. I call it instead, anovulatory androgen excess (AAE) because not ovulating normally is part of the cause along with an inherited risk; AAE is very treatable and reversible (a topic for another day).

“Do I need some kind of treatment?” 

We do not need to treat irregular, far apart or absent menstrual cycles during the first year after menarche.

There is no clear answer, however, when young women are two to 10 years following menarche. Why? Because although we know that silent bone loss occurs in women with abnormal cycle lengths or ovulation (Kalyan 2010) no study has followed teens with both normal and abnormal cycles monitoring their cycles, ovulation and gain in bone over time. We know something about bone risks from asking about 900 women ages 61-77 who had recorded cycle lengths over at least five years when they were in their mid-20s, about whether or not they had experienced a broken bone (Cooper 1997). Those with a later age at menarche or with persistently longer cycles were at increased risk of osteoporosis. Those who regularly had cycles longer than 31 days in their mid-20s to mid-30s were at increased risk for fragility fractures when they were older (Cooper 1997). The majority of the fractures occurred more than 10 years into menopause but 11% were in women who were still menstruating (Cooper 1997). From the same study, those with a later age at menarche (older than or equal to 14) were more likely to have a wrist fracture (Cooper 1997).

Our recent meta-analysis of six groups of women (from teens to the late 30s) all studied over time and recording cycles, ovulation and bone changes, showed that those within each group with regular cycles but more versus fewer ovulatory disturbances (anovulation and short luteal phases) were losing on average almost one percent of their spine bone a year (P =0.04)(Li 2014). Far apart menstrual cycles in the 20s and 30s that may have more ovulatory disturbances, although this wasn’t monitored, potentially can cause silent bone loss (as shown in other studies) and an increased risk for osteoporosis 30-40 years later. That means whatever treatment is used for abnormal cycles in older teen and young women needs to be effective at increasing bone density and strength.

“Mom made me go to the doctor who wrote me a prescription for the Pill to regulate my cycles. My mom doesn’t know I haven’t started it yet. I’m not ready for sex. What do you think?”

Your current “whacky” cycles are probably normal since she you are still in your first year of menstruation. For that reason alone, my answer is No. However there are a host of other reasons to avoid use of any formulation of the Pill with synthetic versions of both estrogen and progesterone, also known as combined hormonal contraception (CHC), in teenaged women like you.

Reasons for not using CHC to treat abnormal menstrual cycles:

1. Girls who are not sexually active, nor intending to be soon, do not require contraception.
2. Although blood clots are rare in teens, even the lowest dose combined hormonal contraceptives (CHC) are associated with a tripled risk of blood clots (Dinger 2014).
3. The “job” of CHC is to suppress the hypothalamus. Normal hypothalamic function is needed for your menstrual cycles to mature to regularity in length and normal ovulation.
4. Evidence says that CHC use in teens with normal menstrual cycles causes them to gain less bone than they should for their age (Scholes 2011, Polatti 1995).
5. There is no evidence that CHC treatment for abnormal menstrual cycles causes bone to increase to normal for same-aged women (Liu & Lebrun 2006) or aids in recovery of normal cycles when CHC is stopped (no studies).

“But if my period doesn’t sort itself out after a year, what should I do?”

Jerilynn C. Prior BA, MD, FRCPC, ABIM, ABEM is a Professor of Endocrinology and Metabolism at the University of British Columbia in Vancouver, B.C. She is the founder (2002) and Scientific Director of the Centre for Menstrual Cycle and Ovulation Research (CeMCOR).