The size of the gestational sac on the 35th day of pregnancy is about 0.5mm, but there will be individual differences. Women with regular menstrual cycles can test for pregnancy on their own by using early pregnancy tests when they are overdue for menstruation. After a positive result confirms pregnancy, the earliest intrauterine gestational sac can be seen by ultrasonography on the 35th day after menopause, with a size of about 0.5cm, but the size of the sac can vary depending on the menstrual cycle and the period of ovulation. After the intrauterine pregnancy is confirmed on the 35th day of menopause, those who are in good condition can follow the doctor’s instructions to have a follow-up examination in about 1 week to know the condition of the fetal buds and the fetal heart. However, when there are symptoms of miscarriage such as abdominal pain and vaginal bleeding, it is necessary to take into account the results of progesterone and HCG (human chorionic gonadotropin) test results, and follow the doctor’s advice to preserve the fetus.