The pull-out method (removing your penis from the vagina right before ejaculating) has controversially been used as a way avoid unwanted pregnancy against the advice of medical experts—and for good reason.
Although you are improving your chances of not getting someone pregnant by not directly ejaculating inside them, there's still a little thing known as precumthat could render this method completely futile.
What is precum and what is its use?
Precum is a clear fluid that secretes out of the penis when a man is aroused. It is often found on the urethra and essentially acts as a natural lubricant both to facilitate intercourse and help the sperm travel out of the body.
Whereas sperm is produced by a man's testicles, male pre-seminal fluid comes from the Cowper's gland: a pair of pea-sized glands that are connected to the urethra by ducts. Since ejaculate and urine both come out of the penis from the same tube, the urine's acidity level can actually affect the quality of the sperm making it harder to fertilize an egg.
Being an alkaline mucus, precum can neutralize the acidity left over by urine, clearing the path for sperm to exit the body without compromising its integrity. The quantity of precum secreted varies from one person to another, but generally speaking, most people leak up to 4ml at a time.
Can precum cause pregnancy?
Though precum itself doest not contain any sperm, it can very well pick some of it up lingering in the urethra on its way out. For instance, if you have ejaculated recently before having intercourse in which you secreted precum, trace amounts of live sperm can mix with pre-seminal fluid and eventually make its way to an egg.
One study found that 41% of men had precum that contained live sperm. However, if precum comes in contact with the outside of a vulva, the chances of that resulting in a pregnancy are highly unlikely.