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Usually having intercourse just before your periods/menstrual bleeding or during your periods/menstrual bleeding does not result in pregnancy since the chances of egg being present in your system is minimal. For a regular menstrual cycle of 28-30 days, the usual fertile days would lie between days 8-18 taking day 1 as first day of bleeding. If you are sexually active without additional protection around ovulation time, chances of pregnancy are possible. If fertile mucus had been present at time of intercourse, sperms can stay alive for 5-7 days and fertilize the egg upon ovulation. After ovulation, egg has about 24-48 hours to get fertilized. Wait and watch for your periods. Look out for development of any other new symptoms if pregnancy is suspected. If periods do not start within 10 days of expected period dates, or if you get abnormal periods, or if you suspect chances of pregnancy, consider visiting your doctor/gynecologist at the earliest for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). If pregnancy gets ruled out, and if you are not ready for pregnancy, but intend to remain sexually active, you should consider getting started on suitable regular birth control measures to be protected (after your periods). Avoid unprotected sexual contact within 2-3 weeks of getting started on hormonal contraceptive (as most of the hormonal contraceptives start giving you effective protection after 2-3 weeks). Be regular with birth control use as instructed. Avoid having unprotected sexual contact if you are not ready for pregnancy.
Take care.