The dark area of pregnancy may turn into a gestational sac after one week in general, but it is not absolute, and it may not always turn into a gestational sac. Usually regular menstrual cycle, usually in five weeks after menopause vaginal ultrasound can be seen in the uterine cavity cystic dark area, normal pregnancy cystic dark area about a week can become a gestational sac. The presence of a dark cystic area in the uterine cavity by ultrasound is not a confirmation of pregnancy, but may be a blood clot, and a blood test for HCG (human chorionic gonadotropin) is needed to determine whether pregnancy is present. If the dark area in the uterine cavity still does not change into a gestational sac after one week, ectopic pregnancy should be suspected. If the dark area in the uterine cavity is accompanied by lower abdominal pain and other discomforts, it is also necessary to go to the hospital to have a blood test for HCG and a puncture of the posterior fornix of the vagina to determine the likelihood of ectopic pregnancy and to make a treatment. After pregnancy, you need to undergo regular maternity checkups and consult your doctor promptly if you find any abnormalities.