Pregnancy is calculated according to the start of the last menstrual period, which is considered a normal cycle start, until the 30th day without menstruation when the urine HCG test shows pregnancy, there will be 30 days of pregnancy at present. When the gestational sac appears, it takes time, as far as possible, from the first day of menstruation, and around the 42nd day you can go to the hospital and register for an ultrasound examination of the abdomen to determine whether the pregnancy is intrauterine or ectopic, because not all pregnancies are intrauterine and there are cases of ectopic pregnancy. However, if you have any abdominal pain or bleeding before 42 days or during the observation period, you can go to the hospital at any time to have blood tests, including ultrasound, there is no time limit for this.