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DEMYSTIFYING MENSTRUATION: U-M professor Sioban Harlow answers questions about a topic many find difficult to approach
DEMYSTIFYING MENSTRUATION: U-M professor Sioban Harlow answers questions about a topic many find difficult to approach

January 11, 2005
BY PATRICIA ANSTETT
FREE PRESS MEDICAL WRITER

Leading women's health experts are paying more attention to menstruation as a vital sign of a woman's general health. Variations may indicate problems with fertility, bone strength, heart disease and other problems.

But the menstrual period remains clouded in mystery and lack of information. Sioban Harlow, PhD, professor of public health at the University of Michigan, has spent her career studying menstruation. Here are excerpts from a recent interview with her about the latest research on menstruation:

Q: How many years will the average woman menstruate in her lifetime?
A: The median age of menarche (beginning of menstruation) is about 12 in our society. The median age of menopause (the point at which a woman has not had a period for one year) is about 51. So a woman can expect to menstruate for 39-40 years.

Q: How long, typically, is the time from one period to the next? How does that change over a woman's lifetime?
A: Twenty-eight days. The common pattern one tends to see is that cycles will be slightly longer in adolescence, perhaps 30 days, and they shorten to about 27 days, on average, in a population. Until age 25, cycles are somewhat more variable. Then, from 25 to 35 there's less variation. Then, in later reproductive life, one starts to get shorter cycles but with greater variability. There's more change in the length of the cycle, from one bleeding period to the next.

Q: How long does the typical period last?
A: Anywhere from two to five or six days, but it can be shorter or longer. Right after menarche, teenage girls may bleed slightly longer in the first five to seven years. As you age, you tend to have shorter cycles, into your 30s, and you bleed a little less. And as women move into the transition to menopause, they may bleed a little more. So over a woman's lifetime, what is usual (in the menstrual cycle) changes.

Q: What do we know about early menstruation?
A: The first six months tend to be slightly more variable, and a girl is less likely to ovulate. At age 25, cycles tend to be more variable. If a girl has amenorrhea (not menstruating), or delays having a period for three months, it suggests something else may be going on.

Q: What percentage of girls develop amenorrhea?
A: About 4 percent of women have cycles (between periods) longer than 90 days, or what we consider amenhorrea. But there isn't wonderful data on that.

Q: How do you define irregularity?
A: I like to use the term variability. How much does the cycle change from cycle to cycle? Is it very similar? Some people perceive a difference of one day as variability. What some have is more variable cycles when younger. There are things a woman needs to be concerned about when this happens. There are conditions such as polycystic ovaries (enlarged ovaries with cysts), which is characterized by amenorrhea or very infrequent cycling. Variability also is associated with insulin resistance and infertility. Women with very heavy bleeding, bleeding through protection or having to double up on it, should seek medical help.

Q: Is it important to keep a menstrual diary?
A: A diary can help girls and women understand what their menstrual pattern is. It can be particularly helpful for girls to keep diaries when they start to menstruate and through the teenage years. Keeping track of the cycle can be very helpful again as women move toward the end of reproductive life and begin to experience the changes of the menopausal transition.

Q: What causes menstrual cramps? What percentage of women/girls get them?
A: Menstrual cramps are associated with contractions in the uterine muscles and with the production of a set of chemicals in the body called prostaglandins. The most effective medications for these cramps are anti-prostaglandins, particularly the NSAIDS (nonsteroidal anti-inflammatory drugs) such as ibuprofen (Advil, Motrin). They should begin taking medication the day before they expect their period to start.

Menstrual cramps that begin in adult women can also be a sign of other diseases such as uterine infection, endometriosis or fibroids. About 10 percent to 15 percent of women and girls have severe cramps during most of their periods. About 75 percent of adolescents will have at least some pain with menstruation, and about 50 percent of adult women will have at least some pain with menstruation.

As women get older and get sudden menstrual pain or worsened menstrual pain, that's a sign something is going on. It could be an infection, fibroids or endometriosis perhaps. Heavy bleeding is associated with fibroids, (non-cancerous growths), which we are finding occur in girls earlier than we thought. There are medications for heavy bleeding if it happens more than once and a woman has to change protection frequently. Choice of contraception can make a difference. There's also surgery.

Q: How would you advise parents to discuss menstruation with their daughters? What information should they convey? When should the conversation occur?
A: I would suggest that parents discuss menstruation with their daughters and sons, conveying the basics of the normal biology when young children ask questions and continuing to provide more information when they begin to discuss the body changes of puberty. In addition to the basic information about why we menstruate and menstrual hygiene, I would encourage girls to observe their own bodily changes closely so they understand the rhythms of their own cycle. One important fact to communicate is that maintaining the uterine lining, or endometrium, requires lots of energy, which is why we shed it when there is no pregnancy. That energy demand increases our need for food, and many girls and women need to consume more calories to satisfy their hunger in the second half of their menstrual cycle. It is not really that women develop food cravings before their period; it is just that their body needs more food, so remembering to eat breakfast and increasing food intake can be very helpful.

Q: What should a boy know about menstruation?
A: Just as girls should understand the changes boys go through during puberty, boys should understand the changes girls go through during puberty. Another important piece of information for both boys and girls is to understand the relationship between menstruation, ovulation, and the probability of getting pregnant.

Q: How do you convey a positive view of menstruation when talking about it with children? What words do you avoid or prefer?
A: It is important to explain menstruation as a normal biological function, like breathing. It is one of the normal biological rhythms, and observing that rhythm is important just as it is important to know when our bodies are tired and need to sleep. ... I think it is important to not use negative words and to provide information to help girls successfully manage the pain that can accompany menstruation.

Q: What do you think of menstrual suppression?
A: In the absence of pregnancy and lactation, the normal physiologic response is to menstruate. If a woman is not using contraception and is not pregnant or lactating, then absence of menstruation can signal a health problem and should be evaluated. When women use hormonal contraception of any type, they do not menstruate. The monthly bleeding on oral contraceptives is designed to mimic menstruation by what we call withdrawal bleeding, but the woman is not having a biologic menstrual cycle; the contraceptive hormones override the normal biology. In using any type of medication, it is important to balance the risks and benefits. We really do not know, as yet, whether it is important to mimic menstruation or not when women are using hormonal contraception. That is we do not know the effects on the uterus of long-term contraceptive use without withdrawal bleeding.

It is important to recognize, however, that using hormonal contraception and not menstruating is not biologically the same experience as being pregnant or lactating and not menstruating.

Q: What are some of the bigger questions about menstruation that researchers like you hope to get answered?
A: We are trying to understand more about the patterns that women experience throughout their life so that women and clinicians can know what to expect as women transition into, through and out of reproductive life. Information is very important to understanding the difference between normal changes and abnormality. We are currently very interested in developing a better understanding about the stages of reproductive aging, again so women can understand what to expect as they transition through to menopause. Another major question is how reproductive aging is, or is not, related to other aspects of aging and risks of chronic disease. Finally, understanding how stress affects reproductive function and developing new ideas about how women can influence the health of their reproductive system is a major priority.

Q: How did you get interested in menstruation as an academic subject?
A: When I was a senior in college (University of California, Berkeley), I was interested in women's health and occupational health, and I had to write a senior thesis. I just happened to read a book about menstruation. In the debate about coeducation in the late 1880s, one of the arguments against women going to college was menstruation. The theory was the body needed a certain amount of energy and women would need a certain amount of it during menstruation. When you look at the literature over 100 years, the question always was: What does menstruation prevent a women from doing? So I became interested in the question of how menstruation interferes with a woman's ability to work. I became aware of how little we knew about normative menstrual function and what are the factors that cause problems and alter it. So I've spent my career trying to understand what is the nature of change in menstruation as a woman ages.

Contact PATRICIA ANSTETT at anstett@freepress.com.