When a patient goes to the hospital to check if she is pregnant, she should be registered with the gynecology department. HCG is a protein hormone synthesized by the placenta, which begins to secrete HCG on the seventh day after the fertilization of the egg, i.e., after the union of the sperm and the egg. The HCG test can only prove that the sperm and egg have united and that the pregnancy has occurred, but whether the fertilized egg is laid in the fallopian tube or in the uterine cavity must be further clarified by gynecological ultrasound. If there is no vaginal bleeding, no abdominal pain or bloating, it is usually recommended to go back to the hospital for an ultrasound to clarify whether the pregnancy is intrauterine or ectopic after the menstruation has been delayed for more than 10 days.