PSA: 100% of Condom Failures Occur During those “Fertile Days”

PSA: 100% of Condom Failures Occur During those “Fertile Days” December 9, 2014

File:Field of Flowers (7087988293).jpg
By Internet Law, I am required to include an image of a field of flowers any time we discuss Natural Family Planning.


The Atlantic reports on the increased use of fertility-awareness methods of family planning, especially among us educated-types.  Quick caution if you read the article, take a look at this quote and put on your thinking cap:

Every morning when she wakes up, Becca, a college student in Pennsylvania, puts a teardrop-shaped thermometer called the Daysy under her tongue. If it lights up green, she knows that day she and her boyfriend can have sex without a condom. If it’s red or yellow, they need to use protection.

Now let’s think about condoms.  Some percentage of the time, they don’t work.  We calculate this percentage, roughly speaking, by comparing how often they are used with how often the couple gets pregnant anyway.

Now let’s think about human fertility. Men are fertile (or as fertile as they get) all of the time.  Women, on the other hand, are fertile perhaps 25% of the time.  In a short cycle, it’s more like 33% of the time; in a long cycle it’s much less.  She ovulates one day per cycle (assuming no infertility), and thanks to the generous work of cervical mucus, she can actually conceive if she has intercourse in the week before or the day immediately after ovulation.  Your results may vary, but at most figure a women has about an eight-day window per menstrual cycle when she could conceive.

During that eight-day window is the only time that condom failure can occur.

Add to this harrowing picture the reality that a significant number of women and men are either infertile or much less fertile than the ideal; not every condom-using couple is even able to conceive if they wanted to, and many of those who could conceive actually have far less than a full week of fertile days per cycle.

Meanwhile, when the CDC publishes rates for the effectiveness of condoms (and other barrier methods of contraception), they are assuming that you are blithely using a condom whether you are fertile or not.  The pregnancy rate for condom use lumps together both the times when it was impossible to conceive (most of the time) and the sliver of time when you might have been able to conceive.

Thus if you are using fertility awareness and are counting on a condom or other barrier method to avoid pregnancy during your fertile time, be aware that your contraceptive is much less effective than the number calculated by the CDC.

Not that I have anything against babies.  Go ahead, have a baby! I love babies!  But if you have serious reasons to avoid a pregnancy, Natural Family Planning, properly employed, including abstinence during periods of fertility, is your best bet.


Meanwhile, more thinking-cap moments via The Atlantic: If some 22% of American women are using periodic abstinence to avoid pregnancy, I guess that “No one uses NFP so ignore the Catechism” thing maybe isn’t so true.


h/t to my friend Charity Horinek for bumping the link.

NFP-Awareness Image Compliance courtesy of vastateparksstaff (Field of FlowersUploaded by AlbertHerring) [CC BY 2.0], via Wikimedia Commons

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