For the teenager to know, it is basically taking it before the ejaculatory fluid is ejaculated. It has to be at the correct time. There are high rates of failure. At the brim of ejaculation, it can be discharged prior also. So there are chances that the woman gets pregnant with pre ejaculatory fluid. So it is a non-scientific method of contraception with high failure rate. Second it is open to any sexually transmitted diseases. So it will prevent pregnancies at certain points of time. Contraceptive pills may give a success rate of 99.5% and withdrawal method may give only 70 -75%. There are high failure rates. So our worry in young girls is sexually transmitted diseases. So barrier methods are a must for sexual activity extramarital sexual activity.
