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Heather Corinna replies:
Can a woman become pregnant off of pre-cum fluid alone?
The short answer is that it is possible, yes, but is not very likely.
The longer answer is that there are a lot of variables, and we still need more study to be done on this to give a better answer.
Do we know that pre-ejaculate fluid can contain sperm? Yes, we do. We also know that there are far, far less sperm in pre-ejaculate -- when there are any at all -- than there are in a full ejaculation: a full ejaculation contains as many as 100 million sperm, whereas when sperm is in pre-ejaculate, it's more like a few million, if that many. But it only takes one active sperm and a few hundred helper sperm to create a pregnancy, so sometimes there may be more than enough sperm in pre-ejaculate when sperm are present in it to make that happen. However, sperm also need the fluid they're part of to create a pregnancy, so the limited volume of pre-ejaculate is also an issue, as is the far fewer sperm which may be (and often are not) part of it.
There's no 100% way to know at the time if pre-ejaculate contains sperm, but it's generally agreed upon that it is most likely or only likely to when a man has recently ejaculated and has not urinated afterwards (urine flushes the urethra out, removing traces of sperm). It's generally considered to be least likely to contain sperm when a man either hasn't ejaculated in a while and/or has recently urinated before he's pre-ejaculating.
Since you'll often hear a lot of argument when it comes to whether sperm are or are not present in pre-ejaculate, here's what some other credible folks have to say on the matter:
Go Ask Alice at Columbia University says:
Sperm could be in pre-cum, but only after a recent ejaculation, after which some sperm may be left hanging around in the urethra. "Recent" means masturbating earlier and then having sex with a woman, or during the same sexual episode of the recent ejaculation. Urinating in between ejaculations flushes the urethra of stray sperm and makes the way clear for the sperm-less pre-ejaculate fluid. If sperm remains after a prior ejaculation, then it's possible that they can enter the vagina and make their way to meet an egg.
The Feminist Women's Health Center says about it:
During sex, the penis releases two kinds of fluids. The first is pre-ejaculate or pre-cum, a lubricant made in a gland in the penis. This fluid usually contains no sperm, but can transmit infections. The second, released with ejaculation, is semen, which is made in the testicles and carries thousands of sperm in addition to any sexually transmittable infections that may be present.
Many sources that discuss the ineffectiveness of withdrawal argue that pre-cum can contain sperm. This is because previous ejaculations can leave some sperm behind in the folds of the penis. While there is a need for further study, it is likely that urination before intercourse washes leftover sperm from the urethra, the tube from which both urine and semen exit the penis.
Here's what Student Health Services at Oregon State University has to say:
Pre-cum is the pre-ejaculate fluid that can be released from the penis during sexual activity. It is usually released before the male reaches orgasm, which results in the ejaculation of semen. Pre-cum prepares the urethra for the semen and helps in lubrication during sexual intercourse. Also the pre-cum may contain sperm. Since the pre-ejaculate can contain sperm, a pregnancy can occur if the man's pre-cum comes in contact with the woman's vaginal canal.
However, there is inconclusive evidence as to where the sperm in the pre-ejaculate comes from. Many researchers suggest that the sperm in the pre-ejaculate comes from leftover sperm from a previous ejaculation of semen. These researchers suggest that urinating after the ejaculation of semen will remove any sperm from the urethra, so as to prevent the pre-ejaculate from containing sperm. However, research is still being conducted to support this widely accepted idea.
And here's what Contraceptive Technology has to say:
Some concern exists that the pre-ejaculate fluid may carry sperm into the vagina. In itself, the pre-ejaculate, a lubricating secretion produced by the Littre or Cowper's glands, contains no sperm. A study examining the pre-ejaculate for the presence of spermatozoa found none in the samples of 16 men. However, a previous ejaculation may have left some sperm hidden within the folds of the urethral lining. In examinations of the pre-ejaculate in a small study, the pre-ejaculate was free of spermatozoa in all of 11 HIV-seronegative men and 4 or 12 seropositive men. Although the 8 samples containing spermatozoa revealed only small clumps of a few hundred sperm, these could possibly pose a risk of fertilization. In all likelihood, the spermatozoa left from a previous ejaculation could be washed out with the force of a normal urination. However, this remains unstudied.
So again, the only right answer we can give right now is a maybe.
But we also do know that withdrawal isn't one of the most effective birth control methods, in either perfect or typical use, and that enough people report using it perfectly -- saying they withdrew well before ejaculation -- and still becoming pregnant (including my parents as well as a close friend of mine, for a personal perspective), that we'd be remiss to rule out pre-ejaculate as a pregnancy risk. Bear in mind that during the Baby Boom in the United States -- a period in history when we had more births than any other -- that withdrawal was the most common method of birth control people were using. Of course, many of those pregnancies may well have been due to men who said they pulled out on time not realizing they had actually ejaculated, and we have no way of knowing what the real deal was. What we can know, for sure, are the success and failure rates of withdrawal as a method, however it is practiced, and know that most other methods of birth control are more effective.
Too, unprotected sex, period -- ejaculate or no -- poses risks of all sexually transmitted infections, which should be just as great a concern as pregnancy. And pre-ejaculate can transmit the HIV virus just as much as full ejaculate can.
So, having unprotected sex, period, just isn't a good idea unless you are trying to become pregnant AND you and your partner have both been practicing safer sex for at least six months, monogamously, AND each have at least TWO full and clear STI screens under your belts. While it'd be nice if we had more data on pre-ejaculate at this point, at the same time, it's not all that essential. We already have the essential information we need, which is that ANY unprotected intercourse presents risks of pregnancy and STIs, and that people who want to prevent pregnancy achieve that best with the most reliable methods of contraception, used properly and consistently, or by abstaining from the kinds of sex which present pregnancy risks.
If you want to engage in intercourse safely, you need a condom at a minimum, and if, for whatever reason, that or some other reliable method is not an option, then the only good choice is to choose not to have sex until sound contraception can be used.
Here are some extra links to grow on: