Pre-cum is something that everyone with a penis does when arousal happens. Pre-cum—officially called pre-ejaculate—is a clear, sticky fluid released by the penis between the beginning of arousal and ejaculation. There isn’t an exact moment someone has pre-ejaculate, it just happens sometime during arousal. Doctors believe that pre-ejaculate helps make the urethra and the vagina less acidic, allowing sperm to survive longer. Some people release a small amount of pre-ejaculate; others may release quite a bit.
Although pre-ejaculate does not contain sperm when it is produced, it can pick up leftover sperm in the urethra. This means that pre-ejaculate can contain sperm when it leaves the body, creating a risk for pregnancy. Pre-ejaculate can also transmit STIs.