This is only kind of true. Never say never — it's not impossible. That being said, it's much less likely that you'll get pregnant while you're on your period. If your cycle isn't completely regular, you might not correctly interpret when you're ovulating, Dr. Mark P. Trolice, MD, FACOG, FACS, FACE, the director of Fertility CARE (Center of Assisted Reproduction & Endocrinology), a clinical associate professor of obstetrics and gynecology at the University of Florida in Gainesville and the University of Central Florida in Orlando, tells Romper by email. Additionally, Trolice says that it's normal for some women to spot when they're ovulating, which means it might be bleeding related to ovulation and not your period, so if you have unprotected sex during that time, you could get pregnant. It's still not likely, however, if you're truly on your period, that you'll get pregnant. But you might want to use protection just in case.

While there is some data that says that this might not be true, there's also evidence that it might be. Dr. Leah Millheiser, MD, FACOG, IF, an OB-GYN and clinical assistant professor of obstetrics and gynecology at Stanford University, says that only a very large study would be able to give a definitive answer on this. "The exact biologic mechanism is not well understood," Trolice says. But Millheiser notes that, anecdotally at least, it does seem to happen. "If you have women living together in a dorm situation, in boarding school or college, and if they’re not on the pill, for example, or some sort of hormonal contraception, you will see them start to have menstrual synchrony," she says. "I saw it in college, I see it in people like women who share offices who are not on hormonal contraception; they’ll start to sync their periods with each other. So I do believe there is some truth to menstrual synchrony."

Millheiser says that when she was growing up, she heard that you shouldn't exercise while on your period because you'll bleed more. She says that the general concept isn't true and, in fact, encourages you to exercise if you have cramping or PMS-related fatigue because it can help relieve symptoms. But she also says that it is sort of true that you might notice more blood, it's just not from increased blood flow due to exercise. "What you might notice, while you’re running, is that the blood — like if you’ve been sitting for a long time and then you get up to do strenuous exercise — you might notice more blood coming out just from going from a reclining to a standing position, but that can happen from sitting to walking around," Millheiser says. It's not because the exercise increased your blood flow.

In most cases, intense workouts won't be a problem when you're on your period, but if you have an exceptionally heavy flow, it could be a bad idea. "If the fatigue is related to extremely heavy menstrual cycle and, you know, somebody’s having a really heavy bleed — what we call menorraghia — then that can lead to anemia, so they’re having symptomatic anemia, in which case, exercise would not be a good thing because they’re basically, your ability to carry oxygen is low from having a decreased blood count, so that’s something that needs to be evaluated by a doctor," Millheiser says. "If your eyelids are pale, your tongue is dry and pale, you’re feeling really tired, you’re losing a lot of blood during your period, you’re dizzy, you’re short of breath, that has to be evaluated immediately."

Again, there's only a grain of truth to this old wives' tale. If you're using a tampon or menstrual cup, swimming while you're on your period is completely fine, Millheiser says. But if you only use sanitary pads, you might want to stay away from the water until after your period is over. A pad isn't going to "protect" you the way that other things will, she adds. "But there is no medical reason why you should avoid swimming during your period. If you’re just using pads, the blood is going to come out and it’s going to get everywhere, so it’s better to use a tampon or a menstrual cup when you’re swimming."

First of all, no, if you have a period and have regular symptoms, it's not going to impact your ability to get the job done at all. Millheiser stresses that there are even studies that have been done to show that. "The caveat to that is some women do suffer from something called premenstrual dysphoric disorder that tends to go away within the first couple of days of your period, but what women might notice right before they lead up to their period and for the first or second day is that they have significant fatigue, depression symptoms, difficulty focusing which can affect their work performance, but premenstrual dysphoric disorder is not common," she adds. "This is a rare disorder, but when women have it, it’s quite debilitating. So that's where you may see some challenges at work to focus, to concentrate, those things." So while your period might not affect your ability to do your job, there might be some truth in this old wives' tale for someone else.

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