Flow: The Cultural Story of Menstruation (25 page)

In seasonal ovulation, female animals periodically enter a condition known as “estrus” or, if you’re feeling folksy, “being in heat.” For these animals, their menstrual cycle actually starts before estrus. The uterine lining starts growing, ovulation occurs, and estrus finally kicks in. Estrus is the only time such a female will be even remotely interested in sex, and she will emphatically give any male the bum’s rush if he attempts to pitch woo at another time.

In some animals, an actual physical barrier prevents sex from occurring at any time outside of estrus, acting like a kind of Darwinian chastity belt. For instance, the vagina of a female guinea pig is usually protected by an impenetrable membrane, but exposure to estrogen and progesterone during ovulation makes it magically open up, not unlike Aladdin’s cave, to the lucky male guinea pig. This is not only an effective means of maximizing the investment of sex, but is also a terrific conversation starter at your next cocktail party. Similarly, unless a female rat is in heat, her ovaries don’t secrete any sex hormones, either. And without them, she can’t assume the saucy position known as “lordosis,” in which she arches her back and flips her tail aside invitingly, allowing the right male access to her rodent-y charms.

Other animals (most familiarly, cats and rabbits, but also camels, ferrets, the short-tailed tree shrew, and minks … who knew?) are what’s called reflex ovulators. For them, ovulation is actually triggered by the physical stimulation of intercourse, which makes this perhaps the most efficient way for mammals to reproduce. It’s only female primates, including humans, who can literally have sex anytime they want—without ovulation having just occurred beforehand, and without triggering ovulation in the process, either.

In a small study of women in New York City, 6/ percent said they had had a period when they weren’t expecting it … and we bet the others were lying.

There is, however, an interesting fertility notion floating about that an orgasm can actually cause a woman to ovulate right there on the spot, which would effectively make her a reflex ovulator. Could this possibly be true? In her 1999 book, Woman: An Intimate Geography, Natalie Angier ruminates on the observation that a woman is, in fact, somewhat likelier to become knocked up from sex with an excitingly adulterous lover, rather than with a lawful, presumably boring, husband.

While perhaps the underlying fantasy is that a man’s sexual prowess can be so overwhelming that it can cause even eggs to swoon right then and there, there simply hasn’t been enough research done in this area to prove or disprove this intriguing theory. As far as we know, the process that leads to menstruation is a complex cycle of hormones regularly released over a period of time, month after month, as well as their interplay with organs—not just the obvious reproductive ones, but others throughout the body.

In most animals, if sex doesn’t result in conception, the uterine lining is simply reabsorbed. In humans, however, it’s expelled down through the vagina and out the body—on average, every twenty-eight days. This, however, is a rough average. What’s considered “normal” can and will range anywhere from twenty days to forty-five, even in one’s own lifetime.

In a small study of women in New York City, 61 percent said they had had a period when they weren’t expecting it … and we bet the others were lying. Unless you’re on the Pill and are therefore experiencing that phony-baloney, regular-as-clockwork pseudo-period, perfect menstrual regularity is not unlike sightings of the Loch Ness monster or Bigfoot, rumored to exist but rarely experienced in person. Hitting one’s mark within three to four days is the best most women get—and that usually only happens in one’s twenties and thirties. Even twenty-seven-year-old Joan Benoit Samuelson, winner of the first women’s marathon in the 1984 Olympics, ran with a just-in-case tampon pinned to the inside of her shorts. If you’re in your teens or forties, your cycle will most likely occur in wildly irregular nonpatterns, flummoxing one and all. And for some reason, flight attendants seem to have it the worst—they not only have the heaviest flow, but the greatest irregularity.

At the same time, while the length of a cycle may vary wildly from month to month over the course of one’s life, and from woman to woman, the actual sequence of events that take place within the cycle is amazingly constant.

Do you remember that strange diagram of the female reproductive organs from those movies they showed girls in junior high, the one that so eerily resembled a moose’s head? To us, the uterus and ovaries, projected up there on that giant screen, seemed at least as big as a toaster oven. It’s downright disconcerting for us to realize that, in fact, the uterus is only about three inches long, and weighs a mere two ounces. Held loosely in place by ligaments, it dangles jauntily in one’s pelvis like a sailor in his hammock, tipping and shifting depending on whether one is standing, sitting, lying down, or doing the plow position in yoga class.

The two ovaries are small, vaguely resemble lumpy grapes, and are, at least when you’re young, chock-full of egg cells. And while the shelf life on human eggs is distinctly better than that of a carton of chicken eggs you get at the supermarket, it’s still incredibly limited and inflexible: pretty much fifty years for all women, throughout time, despite any and all advances in diet, medical care, and technology. From one’s mid-thirties onward, one’s egg cells start to degenerate faster than potato salad on a hot day. By fifty, no matter who you are and how much of a health nut you’ve been your whole life, those egg cells are pretty much outta there, long gone, a distant memory. Compare this to when a girl is born—she starts off with about one to two million egg cells. Yet by the time she hits menarche, it’s already down to 300,000.

The ovaries are on either side of the uterus and, like two tough customers from an old gangster movie, are literally covered with scars—one for each time an egg follicle has ruptured, releasing a mature egg during ovulation. The ovaries also produce hormones, the most important being estrogen and progesterone.

The first day of your flow is also, conveniently enough, considered day one of your menstrual cycle. This is when the hypothalamus, that almond-size gland way up in your brain, sends out a hormonal message to its neighboring gland, the pituitary, which then sends out a chemical message of its own, the follicle stimulating hormone (FSH), down to the ovaries. Like the final recipient in a game of Telephone, about twenty follicles and their eggs in one ovary (and the ovaries take turns ovulating, from month to month) thus get the cue to start ripening.

On day ten, only one follicle of the original twenty is allowed to continue developing; if two do so and pregnancy occurs, fraternal twins could be the result. As this follicle grows bigger, its egg matures. In the meantime, the other nineteen follicles and their egg cells dry up and die (which helps explain what happens to at least some of those eggs you were born with). By now, the feathery, hairy tissue tips of the fallopian tubes have begun eagerly caressing the ovary in anticipation of the big O, ovulation itself.

Sure enough, on day thirteen or thereabouts, the pituitary gland up in the brain squirts out another chemical message, the luteinizing hormone, which now tells the fully ripened follicle it’s time to ovulate. Since the ovary doesn’t have any openings, the follicle splits open—which can cause mittelschmerz, the decidedly unpleasant twinge, cramping, or occasional spotting many women experience midcycle—and the egg is pushed out into the waiting tips of one of the fallopian tubes. Over the next few hours, it will travel through that tube, hooking up with any sperm that happens to be hanging around, even from sex that occurred several days earlier. That’s because while an egg is alive for only about twenty-four hours after ovulation, sperm can last a lot longer—anywhere from three to five days, sometimes even more. As a result, a woman is fertile for the time surrounding ovulation for a total of about a week to ten days in the middle of her cycle.

With the egg safely on its way, what’s left of the ruptured, left-behind follicle secretes the hormones progesterone and estrogen. These in turn signal the lining of the uterus to grow.

The lining of the uterus (aka the endometrium) is made up of three layers of mucous membrane. Mucus, for your information, is not just the gooey stuff you blow out of your nose on occasion, but is in fact an important secretion made up of a protein, salts, and water. The top two layers are built on top of the bottom layer, which acts as a base. They’re supplied with blood through three arteries; if a woman becomes pregnant, the egg will attach to the uterine wall, and these arteries will continue to stock the placenta with blood.

But if the usual state of affairs occurs and conception doesn’t take place, the egg either dissolves or gets absorbed into the body. Hormone production abruptly ends, and progesterone and estrogen levels plummet. As a result, the day before flow is due to start, those three arteries cut off blood flow to the uterus, in effect killing off those top two layers of endometrial tissue. Then suddenly, wham, they briefly open up again like a fire hydrant, allowing blood to rush in under the dead tissue, basically forcing it to explode.

And where does it all go? You guessed it—motored by gravity and cramps, it all goes down through your cervix and out of your vagina, that’s where! Cramps are basically uterine contractions, the kind that can ultimately propel squirming babies out into the waiting world.

This, then, is menstrual flow—the mysterious stuff people have been making such an unholy racket over all these centuries. All told, it’s only about two to three ounces, or four to six tablespoons’ worth, of blood, mucus, and uterine tissue. That’s all menstrual flow is. Made up of familiar ingredients any woman has lying around her body, it’s not inherently poisonous, dangerous, or teeming with weird diseases. The blood is identical to the same old blood that comes out of your finger when you accidentally stab it with a bagel knife, with one exception—since it has relatively few platelets, menstrual blood doesn’t clot. Those impressive clumps occasionally found in one’s flow aren’t actually congealed blood, but bits of uterine tissue from those top two endometrial layers.

So if you do the math from day one (the first day of your period), you’ll notice that ovulation takes place about two weeks later. But since sperm can hang around in your fallopian tubes for several days waiting for some action, this means that the two weeks or so after your period ends is an especially fertile time. Having sex during your flow doesn’t mean you won’t get pregnant, either. For one thing, it might not actually be a period, but the occasionally heavy spotting many women get at ovulation, i.e., their most fertile time. What’s more, it’s possible for women with extremely short or, weirdly enough, very long cycles to be ovulating much closer to the time of actual bleeding. If you really don’t want to get pregnant, just make sure to use protection every time you have sex.

This elaborate Kabuki dance of glands, hormones, eggs, and follicles is, of course, totally missing when one is on the Pill. During the three weeks one is ingesting the active estrogen or estrogen/progestin-containing pills of one’s packet, the hapless body is chemically hoodwinked into thinking that it’s pregnant. Mission seemingly accomplished, it then feels no need for its usual hormonal Morse code relay from brain to uterus, that crazy monthly Battle of the Eggs, ovulation itself, the fallopian wide receiver catching the egg and transmitting it to the uterus. Being on the Pill essentially suppresses the ovaries’function, which may explain why it also significantly decreases the risk of ovarian cancer. Furthermore, while there is a mild building up of the endometrium during this time brought on by the low levels of synthetic hormones, it’s nothing like the usual heavy feeding of the dense, blood-gorged nest waiting for implantation. All of this explains why one’s period—the flow, the cramping, the symptoms—is invariably so much milder when one is on the Pill than not: because it isn’t really a period at all.