Still, if you’ve had consistent periods in the past, it can be jarring when your cycle suddenly becomes shorter than your usual—and even stranger when it stays that way. But why do menstrual cycles and periods get shorter, and what can it indicate about your overall health? Here’s what you need to know. “The hypothalamus controls your cycle,” explains Christine Greves, M.D., a board-certified OB/GYN at the Winnie Palmer Hospital for Women and Babies. “If you’re exercising at a very intense level, your body may detect that it’s not a good time for you to be reproducing and interfere with your ovulation.” As a result, “you may be building up a uterine lining but not getting the signal to shed it from lack of conception,” says functional medicine gynecologist Wendie Trubow, M.D., MBA. What’s more, she adds, “if a woman is exercising enough to disrupt her ovulation, then she may be also suppressing her estrogen levels, which can lead to shorter periods since a woman doesn’t build up enough of the uterine lining and so, less sheds and shorter menstruation.” However, an older study3 found that women who work in stressful jobs are twice as likely to have short periods as those who work in jobs that aren’t considered stressful. “Extreme stress can affect cycles by interrupting ovulation or delaying ovulation,” Lew says. This can cause your periods to get shorter and lighter, the ACOG4 explains, although some women may have heavier periods—it really depends on your body. Your periods may also start to come further apart, according to Lew. A typical cycle can be anywhere from 21 to 45 days, according to the ACOG1. But, again, you know what’s normal for you. The biggest reason you might notice your cycle getting shorter is poor ovulation, says Mary Jane Minkin, M.D., a clinical professor of obstetrics and gynecology and reproductive sciences at Yale Medical School. “When we ovulate—around mid-cycle in general—the ovary turns the area from which we ovulated, the follicle, into a producer of progesterone,” she says. “Progesterone turns the lining of the uterus into an area where a fertilized egg would like to implant.” If there’s no fertilized egg, the follicle that’s making progesterone dies, she says. Then, the progesterone levels fall and you have your period. “Anything that leads to poor ovulation will lead to less progesterone, and you will get your period sooner,” Minkin says. Just like with shorter periods, this can happen with age, after you have a baby, and when you’re breastfeeding, Minkin says. “If you get one short cycle, I would ignore it—no evaluation is necessary,” Minkin says. “But if it keeps on happening, a check-in with your gynecologic provider may be worthwhile.” However, Lew points out that there is a range of what’s considered normal in medical terms—namely, cycles of every three to six weeks, with a period that lasts two to seven days. If your cycle is outside of this range or has suddenly fallen outside of it, she recommends checking in with your doctor about a possible evaluation.
