A 22 year old man had unprotected sex with his friend. He said that it was his second attempt in a night, the first being masturbation. He claimed that he had washed his organ properly before the next act. He was sure that there was no discharge in her but was worried about pregnancy. I asked him to wait for his girl friend to have her periods on the expected date. If she missed it, they better rush to a gynaecologist.
The penis is capable of re-erection after a sexual encounter after a lag period, which varies from individual to individual. Penetration in the vagina is possible when the penis is in erect position. The past sexual fantasy (masturbation in this case) has no relation to the present sexual encounter (when he penetrated his partner).
Washing immediately after masturbation may help in getting rid of the ejaculated semen. However, semen is released in subsequent sexual encounters in majority cases. The pre-ejaculated fluid may also contain sperms at times. Even a single sperm is capable of making a female pregnant. He was requested to use some form of contraception like a condom before indulging in any sexual intercourse.