Hi Welcome to HealthcareMagic Pregnancy can occur when sexual intercourse occurs around time of ovulation. Timing of ovulation depends on length and regularity of menstrual cycle. In a normal regular cycle ovulation occurs 14 days prior to next expected periods. If Your cycle is of 30 days or less and its regular then pregnancy is rare. In case of doubt you can always use emergency contraceptive within 72hrs of unprotected intercourse or confirm pregnancy by urine pregnancy test if periods have been missed. Take care.