Birth control pills are supposed to be something like 99% effective. So I’m curious- how can they fail? I understand the woman is supposed to take one pill every day at the same time. Can taking it a few hours late one day cause a pregnancy?
Also, are there some kinds of prescription medication that could conflict?
Yes, some prescriptions can conflict; I’ve been told to stay away from St. John’s Wort, and certain (rarer than people think) antibiotics. Most times the pill fails, though, is because people miss one. Missing one is variously dangerous depending on where you are in your cycle. For optimal results one should take them at the same time every day; it helps you never forget one, but taking one a few hours late shouldn’t really do much harm unless you’re a habitual pill-forgetter.
I take mine continuously, however, and if I’m more than four hours or so late on one I’ll have breakthrough bleeding and have to go through a normal period before I start up again. I really don’t think that this is a pregnancy risk, but it does suggest that not keeping the hormones steady over time can have some effect.
Still; the “typical use” is so much lower because people foret.
Like Zsofia said, as long as it’s not due to another medication, it’s about forgetting. My doctor gave me a figure of something like four to six hours after your normal time where you’re still okay if you forget it (though not if you do this habitually). Miss by more than that and you should use back-up contraception for the rest of the pill cycle.
I’ve actually found that having to be such a nazi about taking my BC on time has done a lot to help me take my other meds–before I got on the pill I was always forgetting them.
Another way is if you take the pill when you’re sick - ie throwing up and crapping - even if you take the pill at the right time, your body doesn’t have the chance to absorb it - do this for a couple of days and you could be in trouble.
Primarily I think it’s user error, as the other posters have said, however.
At least two articles about seasickness in boat magazines have warned that seasickness can cause pregnancy. If you barf, and you’re on the pill, use some other contraception until the start of your next cycle.
The Planned Parenthood website (I’m at work, no link) says that only 28% of women take the Pill correctly. With those stats, its success rate of 95% (with typical use) is very, very good. When used perfectly, it is over 99% effective.
Some oral antibiotics can interfere with the Pill, and (IIRC) you should use a backup method as long as you are on the antibiotics.
Even with absolutely perfect use, it’s still only 97-99% effective, depending on what cite you’re looking at. So one of the ways it can fail is to just not work.
And note that the effectiveness rates are calculated as how many women out of 100 don’t get pregnant within a year of taking it. So a 99% ideal effectiveness (i.e., woman takes it perfectly each time, doesn’t barf it up, doesn’t take conflicting meds) really means that out of 100 women who took it perfectly, 99 weren’t pregnant after a year. That means that one is, and is possibly angry that the pill didn’t work for her.
I have a 4 year old grandson that arrived via oral antibiotics and their interaction with birth control pills.
Isn’t there a small percentage of women for whom the pill simply doesn’t work? It doesn’t affect their body chemistry, or something? Is this an issue of dosage, or something else?
Only Rifampin has been shown to decrease BCP effectiveness. Anecdotes abound about women getting pregnant on the pill while on other antibiotics, but no studies have borne this out for any antibiotic other than Rifampin.
Of course that doesn’t mean it’s not possible, just not proven.
If you take it correctly, you won’t get pregnant. I have been taking it for 11 years, and haven’t gotten pregnant while on the pill. If your girlfriend got pregnant, it was because she didn’t take it correctly.
p.s. The 99% effectiveness that the pharmaceutical companies must disclose is not based on a sample population who take it 100% perfectly. Unless the researchers/drug companies monitor the women 24 hours a day, 7 days a week, there is no way to know if they took it perfectly. It is a sample, which means some of them did it perfectly, and some people didn’t. So average them together, and you get 99%.
Not so. There is a failure rate of under 1% or around 1% for 1 year of perfect use, not for regular use. Just because you didn’t get pregnant for 11 years only means that for each of those years, you - not surprisingly - didn’t roll that 1%. Essentially, you had only 11 chances to hit that 1% mark and did not.
I’ve taken the pill sometimes perfectly, sometimes imperfectly, for several years and not gotten pregnant, but I certainly wouldn’t extrapolate from that to say anything at all about how effective that means the pill would be for others. Every woman’s body is different, and some may not respond properly to the hormone dose in a particular pill.
I am inclined to be skeptical of this claim. In the studies they do - the clinical trials of these pills - there is no way the researchers can completely monitor a woman’s usage of the pill. There is no way they can verify 100% that the woman took the pill perfectly - at the same time every day, and without contraindicated medicines, and without any sickness, etc. Unless the researchers were physically with the woman every day for the duration of the trial watching them take it at the same exact time every day, there is no way to verify “perfect use.”
In these trials, the way they gague “perfect use” is through the subject’s account. The subjects are asked, did you take it perfectly? And their answer is trusted. But in reality, the true accuracy of the subjects’ statements has a wide margin of error, so that must be factored in.
So I am inclined to think that, if there really was a reliable way of monitoring “perfect use” in a trial, then the actual failure rate would be much much lower than 1%.
IMO a substantial chunk of the “it failed” cohort is due to the impact of FTTIAOP (forgot to take it accidently on purpose). More than a few women make unilateral executive decisions to become pregnant, because of a desire to make their relationships with an SO exclusive, or simply because they wish to be mothers.
The "about 1% " failure rate is listed for “perfect use,” and that number was arrived by from animal testing (where they can monitor 24/7.
Human testing has never reached 99% success. The studies I’ve seen are around 95%, including women who report taking it incorrectly.
From planned parenthood:
And I’ve never seen a study, but I think that Astro is (sadly) right. Which is why you fellas should always wear your rubbers, no matter how much you trust her.
I don’t know about the statistics, but my best friend was adamant that she did NOT want children. She took her pill every day at the same time and never missed one. And she got pregnant.
I’ve known other people who say they were taking their pill properly and still got pregnant, but I don’t trust them. With my best friend, I know for a fact how anal retentive she was about taking that pill.
She wanted to sue Ortho-Tri Cyclen. haha. Her kiddo is 3 now.
New studies have shown birth control pills to be less effective in women who weigh more than 155 pounds. Here’s a Link
Further, I was considering doing a drug study about ten years ago (not for the pill). I was advised that each participant would report to the clinic at the same time every day to obtain and ingest their medication in front of the researcher. They would be asked questions about their general health, any medications or herbal supplements, etc. Also regular blood tests were to be done to rule out infection, other drug use, etc. So no, they do not have to rely entirely on the participant accounts in order to obtain “perfect use” statistics.
I think your “substantial” is a bit overboard and rather vague. Are there SOME women that use this tactic? Probably. There is a “substantial chunk”? Now I want proof.
My gf’s best friend is one of those whose bc failed cause of antibiotics. My mum threw up her pill when she was much younger and got pregnant.
My gf is on implanon, a bc implant, which according to the notes that come with it has a hundred percent success rate. It’s only downside is that 1 in 10 women will have trouble with it.