A woman who has two days left to menstruate can test if she is pregnant. The most reliable way to detect pregnancy is to take a blood test for HCG, which is called human chorionic gonadotropin and is a protein hormone secreted by the trophoblast of the placental syncytium. Therefore, the earliest time to detect pregnancy is the eighth day after the formation of the fertilized egg, when the HCG level in the mother’s blood can be detected. The time of ovulation is 14 days before the next menstrual period, so if the menstrual period is only two days old, ovulation is at least 10 days old, and it is possible to detect pregnancy by drawing blood for HCG two days before the menstrual period.