Will pre-ejaculate impregnate a girl? There's been many rumors that it will and won't at school. A lot of my friends who don't use protection and are sexually active say it can't, but I do not know.
A study was done was done in 2011 of 40 samples of pre-ejaculate fluid from 27 men. The samples were gathered from men masturbating prior to ejaculation. Eleven of the men had sperm present in their per-ejaculate fluid. Ten of the men had active sperm (capable of getting a woman pregnant). When sperm was present, it was in all their pre-ejaculate fluid. The amount of sperm was low. All samples had less than 23 million sperm cells, though they noted that one contained more than 23 million sperm cells. The researchers said, "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." [Sperm content of pre-ejaculatory fluid, National Institute of Health, 14 March 2011].
The study also noted that they only collected one pre-ejaculate sample per ejaculation. It is possible that more sperm was present. They also noted, "It would appear from our study that some men repeatedly leak sperm in their pre-ejaculatory fluid while others do not."
So the answer is yes, you can get a girl pregnant with just pre-ejaculate fluid.