At first blush, period tracking apps seem like a convenient, simple way to track one’s menstrual cycle. After all, if you’ve upgraded your paper calendar to an app on your phone, it stands to reason all the stuff you used to put on your paper calendar — including period-tracking — may have gone digital as well.

When it comes to menstruation, though, period tracking apps may not be the best idea. Apps like Flo have faced class-action lawsuits over allegations that the developers shared user information with third-party companies without the users’ consent; others have similar security issues.

But nothing has triggered more scrutiny and fear around period tracking apps than last month’s Supreme Court’s decision overturning Roe v. Wade. As the nonprofit Electronic Frontier Foundation notes, people are most likely to be criminalized for their pregnancy outcomes when a third party like a healthcare worker or family member reports them to law enforcement who “may pressure them into a device search.”

Such investigations commonly use “text messages, emails, browser search histories, and other information that could straightforwardly point to someone’s intention to seek an abortion,” the EFF explains.

Of course, period tracking didn’t begin with the advent of the smartphone app. There are plenty of high and low-tech ways to track your menstrual cycle. Here’s what you should be monitoring and why it’s so important to do so.

Why is period tracking important?

Lisa Masterson, a board-certified OB/GYN in California tells Inverse, “Periods act as vital signs for women and you can obtain great insights into your health and biorhythms and fertility by tracking your period.”

Not only is a missed period one of the first signs of pregnancy, but irregular periods can also be a sign of hormone or thyroid issues, irritable bowel syndrome, and other medical concerns.

Fadwah Halaby, a certified nurse-midwife in Florida agrees. “Knowing more about your own body is always a good thing,” she tells Inverse. “I think we sometimes just hand that over to doctors and are not always interested in how our own body works…But I think that’s really important for women.”

What’s the best low-tech way to track your menstrual cycle?

When the Planned Parenthood lady came to my middle school to explain all the puberty stuff, she told us to write a P on the first day of our period as a way to track our cycle. The first day is important, says Halaby, but it’s not the only thing that matters. To understand what does, we first have to understand other parts of the menstrual cycle.

Most important for people trying to get or avoid pregnancy is the ovulation phase. That’s when a mature egg is released from the ovaries. People with female reproductive organs “typically ovulate 11 to 14 days before they bleed,” she says. That information in isolation doesn’t necessarily help if you’re trying to conceive or trying to avoid conceiving, Halaby adds. “You have to historically look at what your pattern is.”

Knowing that pattern can orient you in your cycle and give you an idea of when you will ovulate. “If you have a 28-day cycle, that’s going to be anywhere from 14 to 18 days after the first day that you had your last period, or 11 to 14 days before the first day you bleed,” Halaby says.

The day before you ovulate is when you’re most likely to get pregnant, but really anytime during the ovulation phase of the menstrual cycle is when people who are trying to get pregnant are advised to try.

While an egg can only be fertilized within 12 hours of ovulation, sperm can survive in the female reproductive tract for up to five days. Thus sex as much as five days before ovulation can result in pregnancy.

Masterson laments the security issues posed by period tracking apps in a post-Roe world. She had previously recommended using period tracking apps “not only to depict period irregularities but to use it in comparison with other metrics like PMS symptoms, athletic performance, libido, energy level, etc, and see how changes in your hormones affect different aspects of your life,” she says.

Those things can still be tracked with a detailed paper calendar or journal, says Halaby, though admittedly, an app can analyze and synthesize data more quickly and efficiently than most humans can.

Good things to include in your period tracking journal or calendar are PMS symptoms (what they are, when they started, how long they lasted) as well as things like diet and when you had sex.

You may be able to use that information to adjust things like your diet, for example, if you notice that when you eat wheat before your period you feel more bloated, you can alter your behavior,” Halaby says.

Is there a menstruation tracking tech that’s not a period tracking app?

Still, not all menstrual cycle tech necessarily has to be high risk in a post-Roe world.

Charting your basal body temperature (BBT) is one way to know when you’re ovulating. Your BBT is your body temperature when you’re completely at rest. When you ovulate, the spike in the hormone progesterone causes your body temperature to rise very slightly before dropping right before your period. If you’re pregnant, however, your body temp stays high.

In contrast to a regular thermometer, Halaby says, a basal body thermometer is much more sensitive, tracking your body temperature to 1/100th of a degree. For example, it could tell you that your body temperature is 98.67 degrees, whereas most regular thermometers would only tell you it’s 98.6 degrees.

You have to take your BBT first thing in the morning before you drink coffee or even get out of bed, Yalda Afshar, an assistant professor of Obstetrics and Gynecology in UCLA’s Division of Maternal Fetal Medicine tells Inverse. It’s also less about what your temperature is on any given morning and more about using recurring shifts in temperature to track the pattern of your cycle over several months.

“You’re most fertile the day before you ovulate,” Afshar says, “so knowing when you’re ovulating is really about understanding a trend and trying to guess, based on previous history, what the next cycle will be.” However, Afshar warns, “it’s definitely not a good way to prevent or promote pregnancy overall, because all it does is tell you that ovulation has occurred.”

She adds that “we’re not robots; we are human and any number of factors can change our body temperature, like medical conditions and medication.” That’s why tracking BBT — or your period for that matter — is about “fertility awareness, not contraception.”

Tracking your menstrual cycle is important and in lieu of period tracking apps, you can always go with a tried and true option that women have been using for decades: a paper calendar.