Cumulative contraception failure over 5 years
While surfing tonight, found this site on birth control, including the following paragraph:
"If your method of contraception has an average failure rate of eighteen percent over five years, your likelihood of pregnancy is greater than fifty percent. Figure that during those five years, 63 out of 100 womenwho used a diaphragm will have become pregnant at least once. The average woman with reversible contraception can expect 2 unintended pregnancies in her lifetime... even a low annual risk of contraceptive failure implies a risk of getting pregnant during amany years of use."
Of course, there are contraceptive failures, but to me that's as though the person who manages this website is saying that a woman who uses even effective contraceptives (pill, depo) WILL become pregnant in a few years or so time, even if using it correctly!! This goes against what I have been taught about contraception...the whole point, after all, is to prevent pregnancy! I know that women can use the pill for 10 years or more and never have a pregnancy, or depo for a year or two. In fact, I always thought that the longer a woman uses her method, especially if it's a hormonal method, will only decrease her chances of getting pregnant on her method.
Is this just some misleading info put on the net?
This seems to be a non-sequitur. The statement about an 18% failure rate applies to a birth control method such as withdrawal (which isn't a very good method). If the failure rate is as high as 18%, the author is right. The cumulative pregnancy rate over 5 years will be over 50% and by probability, actually 63%.
For all methods of birth control, there is a theoretical pregnancy rate (assumes perfect use) and an actual rate (imperfect use by humans who forget). Of the major contraceptives only diaphragms and cervical caps approach 18% failure rate in actual use.
Depo-Provera® runs 0.3% in actual use while birth control pills run 3%.
The longer a woman uses a method, presumably she gets more perfect in its use and therefore her pregnancy rate approximates that of "perfect use" which for pills would be 0.1% and for Depo-Provera® is about the same.
I agree that the statement is misleading.