There are days in woman's cycle where plan B has 0% effectiveness.
It's info I posted in another thread on this sub, about a man getting a woman pregnant despite her saying she took plan B.
Most posters (rightly) focused on the possibility that she never actually took it. Relying on a woman's honesty is never a good bet, and if you're browsing that sub I assume you already agree with that statement. But it seems most the posters here are ignorant about really important info about that means of contraception.
Here's a great article, aptly titled Everything You’ve Been Told About “Plan B” Is Wrong.
Now I'll just clear misconceptions I've had to explain to too many guys. The probabilities are approximative, and the vocabulary not clinical at all, to keep it simple (and also to not have to look up every number, but I'll provide links to places where you'll find them).
This is focused on contraception only, not STD prevention, if you want to avoid STDs make sure that every sexual contact is protected with a properly used male of female condom, or a dental dam
The planned parenthood website is great for learning more, but a lot of the info will not be very useful to a single guy who wants to be able count only on himself (and not rely on trusting anyone else). Of course the best case scenario is two people having sex who'll both have their own ways to deal with contraception, but I wouldn't want to entrust my future on someone else's decisions.
First the basics of how different contraceptions work : Plan B works by preventing ovulation. Because sperm can remain inside a woman for days, and still be able to fertilize an egg. So once a woman ovulates, and there is fertile sperm inside her, fertilization is possible (i.e. "pregnancy").
So if the woman is ovulating at the time you're having sex with her, and not using hormonal birth control, the only way to prevent pregnancy is avoiding contact between sperm and her egg (male or female condom, diaphragm, sponge, IUD... whatever). Plan B would only prevent ovulation from happening after taking it, while fertile sperm is inside the woman (if ovulation has not occured yet).
Spermicide (if used alone) would work marginally (reduce the risk of pregnancy, but there would still be significant danger).
Pulling out, if done right, can b surprisingly effective (~96% success) but still a risk. Other methods considered effective (if used correctly) have at least a 98.5% effectiveness.
And of course I'll add the male MGTOW specific perspective on those :
Don't trust anything you can't check by yourself. So a woman swearing she's on the pill/implant/injection, or has an IUD, is no guarantee. A woman telling you she's using a diaphragm, sponge, cervical cap... might either not be using one, using a sabotaged one (on purpose), or just using it wrong.
Also hormonal contraception methods (pill/implant/injection, and to some extent hormonal IUDs) can be defeated by some health issues, or interaction with medication. Here are a few examples even medical doctors forget to tell patients : it doesn't work reliably on women above a certain weight, antibiotics can make them useless, some hormonal issues might also have an effect... So in case some women are reading my post here's a good link about a long list of stuff to watch for, and remember throughout your life to check for new information on that subject (every few years seems there's something new that is found out).
Spermicide is a coin toss (about cuts the chance of pregnancy by half but that's it). Some rhythm methods (if done thorougly and tracking multiple physical signs accurately) can have a crazy high rate of success, but those factors rely on a woman's honesty and intelligence (not something any poster here should want to do).
So find out what works for yourself. As a guy I'd say spermicide + male condom is very good : cheap, can be managed all by yourself, and easy to carry on your person (make sure it's your own condoms, and you can put them on right, because any mistake on your part will drop the effectiveness from about 99% to 75%). Female condoms can be good too, make sure to bring your own (but I've yet to see a woman who prefers these to the male version). The STD protection aspect is of course a nice perk.
Then there's the "holy grail" : vasectomy. But even that has to be done right. Remember to check your fertily yearly after the procedure (might do it less often after some time) because it might revert by itself. Also even with vasectomy and regular tests, there's no 100% effective method. Even if your tests are good and you're still "infertile", you'd just need to have one sperm at the wrong place at the wrong time, or for your vasectomy to naturally revert between tests to make someone pregnant. So even if it's kind of a "lightning hitting you twice" kind of chance, know the possibility is there.
In any case always try to combine two or more methods. And might as well avoid vaginal intercourse altogether if you psychologically can't accept the fact that no contraception method, or combination thereof is perfect (even though combining two effective methods will give you astronomical odds of not getting pregnant).
ここには何もないようです