How to calculate the time of conception

At present, the time of conception is mainly calculated by the first day of the last menstruation. For women with regular menstrual cycle, it is generally accurate to use this method to calculate the menstrual cycle in about 28-30 days. The development of the gestational sac should be seen with B-ultrasound to check whether the gestational week is normal. For some women with disordered menstrual cycle, who often come early or long delayed, it is necessary to calculate the gestational week by combining the size of the gestational sac and progesterone value of the personal B-ultrasound, which cannot be based on the time of the last menstrual period. Of course, the time of conception is not calculated from the time of cohabitation.