Sperm ejaculation at the opening does not usually lead to pregnancy, it is a form of external ejaculation, but it is not a 100% contraceptive. It is very difficult to control this, as long as a small amount of sperm is ejaculated into the vagina and the woman is ovulating, it can lead to pregnancy, so this is not the best way to prevent pregnancy. If you want to avoid pregnancy, it is advisable to wear a condom, which is the best way. Alternatively, a woman can take the pill or have an IUD placed, which are also options.