Depends on the timing. You can only get pregnant when you’re ovulating, which means an egg is mature and hanging out waiting to be fertilized. This is only true for about 36 hours a month.
This isn’t a very good way to make babies, so women also have cervical fluid designed to help keep spermies alive longer. If a man ejaculates in a woman a few days before she ovulates, the sperm are usually able to hang out and survive until the egg rolls in.
So there are probably all told about 5 days a month you can feasibly get pregnant, with about 2 of them being MUCH more likely than the other 3 or so. If you get super sperm that are virtually immortal, they might be able to exist up to 7 days, but that’s pretty unlikely.
@MrItty: Pre-ejaculate itself doesn’t contain live sperm. If a man has ejaculated recently, it can pick up some leftover sperm that were hanging out in the urethra. Spermicides are actually the worst way to prevent pregnancy with typical use. With perfect use, withdrawal is better than the sponge, the female condom, and some kinds of the rhythm method.