An accurate determination of whether a pregnancy is intrauterine or ectopic can be made by ultrasound. Between 30-40 days of pregnancy the gestational sac is small and will not be clearly visible through ultrasound, so the situation can be determined by HCG test. If the pregnancy is intrauterine, the doubling of HCG will be good, while ectopic pregnancy is not conducive to the growth and development of the gestational sac, which may lead to a bad doubling of HCG or a sudden stop of the growth of the HCG value, followed by a slow increase after 2 days, during which there will be obvious stomach pain and falling, accompanied by irregular vaginal bleeding, which should be considered ectopic pregnancy. After 40 days of pregnancy, the development of the gestational sac is more obvious and can be accurately determined by ultrasound.