The chance of pregnancy on the first day of the safe period is very small, but not absolutely not pregnant, because the menstrual cycle is unstable will appear menstrual disorders, can lead to pregnancy, if you do not intend to get pregnant recommended good contraceptive measures. If there is no contraceptive measures to delay menstruation, it is best to observe the time of delayed menstruation, if more than a week need to carry out an early pregnancy test to rule out the possibility of pregnancy, if not pregnant may be caused by endocrine disorders, it is best to check the sex hormone six, under the guidance of the doctor reasonable take drugs to regulate, in order to promote the menstrual flow. You can use a condom or a contraceptive ring, which is relatively safe, and you can also detect follicles through ultrasound, and only if you are sure there are no follicles discharged during the safety period can you have intercourse, the chance of pregnancy is almost zero, and intercourse is safe.