If a man has an erection, there is a fluid from the Cowper's Gland that comes even before he ejaculates. It ordinarily does not contain sperm, but if the man has ejaculated recently, it will carry sperm in it from the previous ejaculation because some will have been left in his urethra from that earlier time. So, if a couple is having sex and he has not ejaculated yet, he can still have deposited sperm in the woman because it would have ridden in on his fluid from the Cowper's Gland.