There are a lot of reasons, including as an indicator of overall health.

> “Changes to your cycle, or abnormalities—like irregular or heavy bleeding, or severe pain—can all signal issues that benefit from medical evaluation,” says Rashmi Kudesia, MD, reproductive endocrinologist and clinical assistant professor of obstetrics and gynecology at Houston Methodist. “If something suddenly changes with your cycle, or your period is late, you may not realize it right away it if you’re not keeping track.”

> If you do keep track, it will be easier to head to your gynecologist if funky stuff starts happening—and easier for them to find out what's going on. Dr. Kudesia also mentions tracking your cycle can be helpful in pinpointing your fertility window and making small lifestyle changes around the time of your period (scheduling extra downtime to combat your low energy, or being mindful of your eating habits when your cravings are in full swing). [0]

[0] https://www.womenshealthmag.com/health/g26787041/best-period...

Gynecologists ask for your period history including how heavy it is. It’s helpful for them to know when you plan on starting or switch birth control methods. They always ask for the last date/length of your period. I’m lucky if I remembered what I had for lunch much less when I last needed a tampon.

In the old world (tm) women used to have a diary/agenda/calendar and tracked it there. The trend is not "track everything": if you have an idea that makes women carry less stuff with them, I assure you there is a market. their bags.

Data from those apps is really valuable from a marketing perspective.

The case with least value is selling it to P&G or whoever just to track how much market share do they have.

If you put a tracker on it (facebook, for example) you can build a custom audience on top of it and promote/sell whatever you want related to reproductive healt and/or sexuality. Not just women.

You could be a little evil and sell women tampons before they have menstruation.

You could be evil and build a custom Facebook audience with users from your app and make money selling them stuff using a retargeting bid (since they are part of your audience).

Or you could be very evit and target partners of women whe ceased to use your app for more than, say, 3-4 months and show ads for DNA paternity tests (which you don't sell, but someone else does and gives a referral fee for it).

Or you could have very, very evil and build an audience around partners of women who might be pregnant, capture the clicks to build another audience (this time yours) and sell porn, tinder, dating/e-whoring, and divorce advice for a fee. Will work because this is a retargeting list (you already marked them as your customers, so bidding will be low for the ads).

Advertisers can sure be creepy can't they.

Maybe FB audiences should be made public, or you're told if you're in one. It seems a lot more invasive than other Ads software I've looked into (from the perspective of what you could do).

Just do all at the same time. That's the path to maximum shareholder value, assuming you can avoid turning it into a scandal.

I think I'll quote this comment on my "why advertising is a cancer on modern society" list.

Might be missing something here, but why would women who might be pregnant be a particularly valuable audience for porn sites, tinder, etc?

Not the women - their partners.

And to clarify, it's not always because of ill intent of the partner. Depending on preexisting issues and new conditions caused by a pregnancy, it's not uncommon to get an advice from doctor (or even a written advice from the hospital) to refrain from sexual activity. This makes the partner a much more interesting target for aforementioned sites.

And for more clarity, this can swing the other way, too. Sometimes pregnant women want sex more than normal, which can be totally fine/healthy depending on the health of the mother and baby. Hormones are extremely powerful and affect people differently.

Damn, man. My evil plan was just to sell menstruating women chocolate.

It really helps with conception/contraception. It also alerts you to changes in your health. Typically you’re tracking temperature, mucus consistency, cervix properties and menstruation. The way it converges into one stat (fertility window) and also potentially assists with a variety of other health areas is very cool.

Going beyond that, we use Kindara and see a lot of women turning it into a generic key-value habit/mood/reminder tracker with emojis, etc. So it has value beyond just health.

Before the app, there was the red felt-tipped pen kept next to the paper calendar.

One has to know when to carry additional supplies beyond the gifter spare and the emergency personal reserve tampons. And when to wear different underwear. And when not to schedule dates. And when to buy chocolate. And when pregnancy is more likely. And when pregnancy is less likely. And when to eat liver. And when to buy analgesics. And when to make travel plans and hotel reservations, and when to not go anywhere for any reason.

ok the eating liver part caught me... i don't know that part. fill me in?

Protein, iron, and B-complex vitamins.

All extremely useful to replenish lost blood.

You only lose ~80ml of blood. When you donate to the blood bank your giving ~500ml and I've never heard of anyone recommending liver, other than not having an empty stomach there's no special dietary changes necessary.

Am I missing something?

> You only lose ~80ml of blood.

That's an average.

Almost all the women I have known occasionally complain about a "heavy month" every now and then. That can be either excessive bleeding in terms of volume lost over a normal time or an excessive time length of bleeding.

And, a 90lb female losing even 200ml of blood is going to feel effects far more than a 250lb male losing 500ml.

My mother ate liver and onions once a month. It might not have been necessary, but it's still something she did.

Iron?

Most people using menstrual trackers will be trying to get pregnant, which is potentially pretty valuable info for advertisers.

Also, for people with irregular cycles, knowing when you (probably) ovulated can help you predict when you’ll start bleeding.

Compared to most health tracking, tracking your menstrual cycle gives you clearly actionable info.

>Most people using menstrual trackers will be trying to get pregnant, which is potentially pretty valuable info for advertisers

New and expecting parents might be the most valuable demographic, period.

In America, where childbirth can easily come with a five-figure price tag, and where half of the people don't have 500 dollars to their name?

this is a strange cross roads. isn't it?

my wife gave birth 18 months ago, we have good insurance and a lot of family that gave us a lot of stuff we needed as gifts. without that we would easily be on the very upper end of the 5 figures by now.

Upper end of 5 figures is somewhere more than $50,000. Unless you went to an out of network hospital, and the kid ended up in the NICU, I doubt the total would be that high.

my largely medically uneventful labor, induction, and unplanned c-section birth at a bay area hospital two years ago cost me a $500 copay, but the insurance paid amount was somewhere in the neighborhood of $38k.

i also exclusively pumped for a year, which cost a few thousand dollars. the pumps alone were $1200. then replacement parts, accessories, random necessities.. can't even count the time and the calorie investment involved (i was eating upwards of 1000 extra calories a day to prevent weight loss).

throw in gear and clothing and...going past $50k for the first 18 months doesn't seem so unrealistic?

I wouldn’t count what the insurance pays to have any relevance, especially with the fuzzy nature of costs in healthcare field.

Also, one pump is required to be provided by the health insurance company by law, and as now, a new pump costs a a few hundred dollars. This is the most popular one:

http://www.medelabreastfeedingus.com/products/573/pump-in-st...

A crib/car seat/rocking chair/stroller can be had for $1k total if you stick to mid level stuff, maybe a few thousand if you go super fancy. Food and clothes might be another few thousand.

I wouldn’t count one’s time cost to be of importance to the conversation either, as it’s universal. If we’re comparing how much money came out of parents’ pockets with a baby versus not having baby, I would say at most $10k for most people, I would budget for $15k though (and lost wages due to time off if you don’t have paid parental leave).

I would include the costs of what insurance pays, because it is in fact part of the cost of bringing a life into this world in the US. You are scratching to prove your point, and keep moving the mark. If you don't want to include what insurance covers, how about including insurance premiums, at least two years worth since you cant just hop on insurance once you get pregnant. Lost wages are another factor, but those can easily cost thousands for many people, i wouldnt minimize those down so low.

based on your math and assumptions i really wonder if you have had a child in the US recently.

I had no idea my daughter costs my entire post tax salary. I wonder how we pay the mortgage?

But look at all these new credit card offers available!

I'd say anywhere where capitalism reigns. Childcare & natal items are all door busters (and expensive) for big retail shops. They know that you are coming to shop, they just need to get you in their space.

If you get a bill but don't actually pay it does it still have a five-figure price tag?

Assuming your insurance company's machine learning algorithm doesn't decide to deny your payout for UNKNOWN_REASON, that is.

I'm talking about with no insurance. You know the debtors prisons were closed a century ago right? It will screw up your credit score for a couple of years and that's about it.

Many uses. Why do people check the weather before deciding whether to pack an umbrella?

Cycles aren't regular, so just adding an event every 27th day in your calendar, won't be of much use to a lot of women.

These apps can get quite good at predicting irregular cycles.

Some apps will give users warnings of the type "PMS starts tomorrow, expect moodswings", or "expect extreme tiredness" and for people who are heavily affected by their period, this can be a big help in controlling their feelings or just understand their well-being.

Because of the monthly hormone cycle, women can have a difficult time getting taken seriously at the doctor. "Your hormone levels are shifting, that's probably why you're experiencing _symptom_".

If you can show it happens throughout the month, and you have specific data relating whatever symptoms you're experiencing with your cycle, you're a lot more likely to actually get treated for the aliment.

Excuse me but what kind of an idiot doctor doesn't know what menstruation is or what it can potentially cause? And you really need to show him an app for that instead of just saying it happens every period? I'd rather change a doctor to someone who didn't sleep through their medical school...

This unfortunately seems to be rather common (at least in the US), John Oliver did an episode on it a short while ago. It has a lot to do with the history of the medical field as opposed to modern Mal-intent. For example a lot of testing was done on men and then that data was taken and also used for women. If you search for "John Oliver medical bias" you'll find the video.

Because lots of weird shit happens to women.

Pregnant or not? Maybe your hormones aren't right - one of the signs is usually change in monthly cycle. Whenever you have to go to the doctor for pap smears and so on, the doctor asks about it. For some folks, their weight determines their cycle length - too much or too little fat can change fertility. Perhaps you get really, really bad PMS (PMDD) and need to take anti-depressants around 2 weeks before the beginning of your cycle.

And more, I'm guessing. I just can't think of another example right now, but in any case, monthly cycles are a big indicator of health issues and can be a great help with life issues as well.

If you have an autoimmune disease, it helps greatly to know when your estrogen and progesterone levels are highest as they both impact the immune system.

A lot of dudes keep track of their girlfriend's periods, because every month there is one "safe" weekend where you can have unprotected sex and get away with it.

This is sometimes called the "Rhythm Method" or "Fertility Awareness" and a lot of men have self-interested reasons for wanting to know this about a woman.

There is a history of apps optimized for this purpose. Some wholesome for married couples to use, and some for skeezy bachelors who want to track multiple women.

https://gizmodo.com/iamaman-period-tracking-iphone-app-for-s...

https://jezebel.com/another-innovative-menstrual-tracker-app...

> and some for skeezy bachelors who want to track multiple women

Isn't this crazy - the amount of work people would put in just to have occasional unprotected sex. People are animals.

It's not crazy. Sex is one of the most fundamental and powerful desires we have. What's actually crazy, in a mostly positive way, is how much control we've managed to achieve over it at individual and social level.

> People are animals

Well, yes, we're really just pretending otherwise. Also agree with TeMPOralL's sentiment :)

Wowowow, isn't it like 10 days that are safe? I might be in very risky territory here.

Within the span of ten days, you can be sure there is at least one weekend.

If there was EVER any doubt about the demographics of HN... Let this be a lesson to everyone that we work and live in a massive bubble.

Why don't you explain him rather than demonizing him in front of all HN audience. Treat others as you'd like to be treated.

I agree that ignorance of other peoples’ experiences isn’t a blameworthy thing. But it does demonstrate one reason diversity is important. A smart person acting in good faith can miss things that are completely obvious to people with different life experiences. We all only know what it’s like to be us.

It's such a basic question that it would be better to do an internet search or read the wikipedia article on the topic. You might as well ask why heart attacks are a big deal.

I might as well ask what are heart attack apps useful for. I wouldn't know what are heart attacks apps for.

Strange/stretched comparison. Menstruation is all about the cycle. Even as a man one would/should know because the basic methods of avoiding pregnancy when having sex should be of interest to men too. Because of the importance of that cycle its also indicative for a woman's health in general (lots of hormonal changes within the cycle; regular blood loss too).

Heart attacks are just point-events on the other hand, they happen and that's that. So knowing full well what a menstruation app is useful for one would still not understand what a similar app for heart attacks could possibly even mean. Calculate your heart attack window? That would be something new indeed, so you are right not to see the point. Just as there is no point in using heart attacks to understand the menstruation cycle.

Plenty of other people already explained. I decided to leverage this as a teaching moment.

Thank you for the kind lesson. I genuinely didn't know.

Your post is much, much more indicative of the demographics of HN and what sort of a bubble people live in than the grandparent.

I think this thread suggests that is not the case, at least as I’m seeing it now. The ratio of informed to ignorant comments is unremarkable for HN.

Wait until you see posts about unaffordable housing in Silicon Valley and you see HN posters wondering how anyone can live off the $100-$160K salaries developers in most of the metro areas in the US make....

One data point is the demographics of HN?

Among other things, trying to increase/decrease chances of pregnancy.

Prediction. Menstruation apps are useful for prediction. Don't want to bleed all over the office furniture at work? It might be useful to have an idea of when you will start bleeding.

If a woman is trying to conceive it could be helpful to predict her fertility window using menstrual cycle tracking. Same with if she were trying NOT to conceive (so-called "natural family planning")

Doctors ask you if you have a regular cycle, the only way to know that is to track your cycle.

If you're having some sort of issue with your reproductive organs you may track your cycle for a few months to try to better pin down the issue.

They’re often used for predicting your next cycle or for fertility planning. Just to satisfy my curiosity, are you female?

As a dude, I use it to track my mood / fatigue for lifting which worked OK.

Whether you are late?