Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site noscvax.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!whuxl!houxm!ihnp4!qantel!hplabs!sdcrdcf!sdcsvax!noscvax!powers From: powers@noscvax.UUCP (William J. Powers) Newsgroups: net.abortion Subject: Re: Who's Life Anyway? Message-ID: <1009@noscvax.UUCP> Date: Sat, 13-Jul-85 15:55:10 EDT Article-I.D.: noscvax.1009 Posted: Sat Jul 13 15:55:10 1985 Date-Received: Wed, 17-Jul-85 21:17:49 EDT References: <556@bgsuvax.UUCP> <283@vaxwalislr.UUCP> Organization: Naval Ocean Systems Center, San Diego Lines: 58 > >> As I understand it (and what I was working from) the pill runs about > >> 99.9% success. Anyone want to look it up/correct me? > >> Jean Marie Diaz > > > > If this figure is correct, then a woman who is on the pill and who has > >intercourse every other night has one chance in six of becoming pregnant > >in any given year. > > > >Jeff Sonntag > > > A 99.9% reliability for the pill means that if a woman is > using the pill and is sexually active, she has a .1% chance of getting > pregnant in a given year, NOT each time she has sex. This last statement is clearly wrong. Though it is unclear exactly what 99.9% reliability means, if the statement is to have any meaning, it can't mean that a women has a 99.9% chance of getting pregnant in a year. First, let me say that such a statistic could certainly be obtained. You would just take data on how many people that use the pill get pregnant in a year (note that this statistic is independent of proper usage of the pill). However, such a statistic is virtually useless, since the result is independent of the number of times one has sex. If I have sex every night or once a year certainly makes a difference in my chances of getting pregnant. Such a statistic would be useless in my being able to judge what my chances of getting pregnant were unless I had some idea of the number of times this average group of women had sex in a year. If I had the answer to that question, however, I could assign some estimate of the probabilty of getting pregnant given that I have sex. The point is that probability of getting pregnant per sexual encounter while using the pill is a useful statistic; the average number of pregnancies for women while using the pill in a year is a useless statistic unless I know how many times they had sex in that year. Secondly, as I have pointed out previously, if a women has sex three times a week, she will get pregnant on average of about once every 6.4 years. That means that she has about a one in six chance of becoming pregnant in any given year. (This result assumes that the chance of getting pregnant while using the pill is 1/1000.) However, it is worth pointing out that this probability undoubtedly includes those cases where someone forgot to use the pill, and other such misapplications of the pill. It is also worth pointing out that by simply abstaining during times that you think you're fertile (the temperature method will give you a accurate way of doing this), then the probability of getting pregnant while using the pill will decrease dramatically. It is interesting to note that in 1979 there were less than 3.9 million births. If we use assume that one out of every four pregnancies end in an abortion (the 1980 figure), then there were about 5.2 million pregnancies in 1979. In 1980 there were about 43.2 million women between the ages of 15 and 45. These figures would imply that the chances of getting pregnant in a year, even when you want to, is about 1 in eight. Either there are a lot of women who cannot get pregnant or the number of sexual encounters is far lower than three times per week. I suspect that it is the latter assumption which is greatly exaggerated. Bill Powers