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In Germany (and most other western countries) it is considered common knowledge, taught in sex-ed, that pre-cum contains live sperm making the Withdrawal/Pull Out Method ineffective.

Translated statistic Source: Bauer Media Group, 2009

I found no sufficient evidence/sources for that statement, nor did I find enough credible sources to debunk it.

According to Wikipedia, the perfect use failure rate (Pearl Index) of the pull-out method is comparatively effective (4% failure rate).

I found conflicting evidence over whether pre-cum contains live sperm. This study says no while this one says yes. Neither has a large number of subjects.

I don't want to talk about the disadvantages of this method, I'm certainly aware that it does not protect from STDs and is still less effective than other contraception methods.

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    I've trimmed all the X/Y stuff out the question, it was completely tangential to it - we dont need to know your knowledge/bias for this to be a good question. – Jamiec Nov 3 '15 at 9:41
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    I've edited the question quite a bit, but I am unhappy with it. It still contains three different claims: Pre-cum contains sperm. The Withdrawal Method is not effective. The Withdrawal Method is not efficacious. They may all have different answers. Note: It's alleged typical use failure rate of 18% is sufficient to explain why it is deprecated in Sex Ed classes. – Oddthinking Nov 3 '15 at 10:23
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    It really depends on how you define "effective". Unprotected intercourse, for example, is typically about 15% effective as a method of birth control. – Mark Nov 4 '15 at 5:15
  • Mark, please provide sources for such a claim. In the wikipedia sourced table unprotected sex has a perfect use failure rate of 85%, so i don't see anything close to 15% only. – James Cameron Nov 4 '15 at 14:11
  • @JamesCameron: I think Mark was doing math of the form 100 percentage points - 85 percent points (failure rate) = 15 percent points (rate of being effective as a method of birth control) . – purposeful porpoise Nov 5 '15 at 0:25
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Firstly, the 4% perfect use failure rate is merely someone's guess, particularly James Trussell as author of "Contraceptive failure in the United States", Contraception vol. 70, pages 89-96:

Our estimate of the proportion becoming pregnant during a year of perfect use of withdrawal is an educated guess based on the reasoning that pregnancy resulting from pre-ejaculatory fluid is unlikely [citations to two 1992 articles]

On the surface, the two studies cited in the question sound contradictory, but it is important to consider the details, especially the experimental methods. Because the 2011 study cites the early study and gives reasoning for the differing results, it should be considered to supersede the earlier study.

The reason why our study was able to demonstrate motile sperm in pre-ejaculatory fluid whereas other studies have failed to do so might lie in the promptness with which we examined the samples. In our IVF unit, the room where men are able to produce their samples is immediately adjacent to the laboratory. We briefed our volunteers appropriately and arranged for an embryologist to be positioned at the microscope awaiting each sample, and we are confident that samples were examined within 2 min of production. After this time, low volume samples can dry out and microscopic examination becomes extremely difficult.

and

the actual number of sperm in the pre-ejaculates was very low.

Furthermore:

It would appear from our study that some men repeatedly leak sperm in their pre-ejaculatory fluid while others do not.

Also, the earlier study asked men to abstain from ejaculation for 3 days. Obviously immediately after a man ejaculates there is still sperm in the urethra. Since most men are ready and able again in much less than 3 days, maybe even an hour or less, there is risk of sperm being present from a previous ejaculation. According to Longevity of spermatozoa in the post-ejaculatory urine of fertile men, motile sperm remains detectable in urine for several hours after ejaculation.

In conclusion, the state of knowledge is merely that there is some non-zero probability of pregnancy for reasons other than ejaculation, plus there is difficulty for a scientist to distinguish between perfect and not perfect use for withdrawal, particularly:

  1. There can be sperm still in the urethra from a previous ejaculation.
  2. Some men leak sperm into pre-ejaculatory fluid ("We are unable to say how this finding might translate into the chances of pregnancy if these samples of pre-ejaculate were deposited in the vagina except that the chances would not be zero" according to the 2011 article)
  3. "Men may be unable to predict the moment of their ejaculation and subsequently fail to admit to this" (2011 article)
  • Your quotes address "Does pre-cum contains sperm?" They do not address the question of whether or why the withdrawal technique fails, and whether men are perfectly aware/in control of their bodies. – Oddthinking Nov 3 '15 at 13:53
  • @Oddthinking I added another reference. I have support for reasons #1 and 2 in the references. – DavePhD Nov 3 '15 at 13:58
  • I agree that #1 and #2 have been substantiated. However, #3 hasn't, and, even if all are true, none of the three have been shown to be the reason that the withdrawal technique fails (assuming it does). Given the original question meanders around three claims, I would simply edit it to say you are only addressing the claim about where there is sperm in pre-cum. – Oddthinking Nov 3 '15 at 14:02
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    Comments are not for extended discussion; this conversation has been moved to chat. – Oddthinking Nov 4 '15 at 12:45
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    @Christian The 4% cited by the question and Wikipedia specifically traces back to James Trussell. – DavePhD Nov 4 '15 at 20:43

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