Welcome to HealthcareMagic. Anytime the penis comes into direct contact with the vaginal area, there is a chance of pregnancy
. It can occur even if there is one minute of contact of semen or sperms with the vagina. Sperms are very motile and as soon as they are in contact with vagina, they travel up in the vagina and may cause fertilization if the intercourse was close to ovulation.
Hope it helps you. Regards.