Ectopic pregnancy, also known as ectopic pregnancy, mainly includes tubal pregnancy (most commonly in the jugular abdomen of the fallopian tube), interstitial pregnancy, uterine horn pregnancy, ovarian pregnancy, incision pregnancy, cervical pregnancy, abdominal pregnancy, stumpy horn pregnancy, as well as other rare and unknown parts of the pregnancy, and the most common type is tubal pregnancy. Ectopic pregnancy is one of the main causes of maternal mortality in the first 3 months of pregnancy, and early diagnosis and treatment of ectopic pregnancy should be given due attention.Can HCG identify ectopic pregnancy? The answer is: there is an important reference. HCG is secreted by the trophoblast cells of the placenta, which increases the secretion of progesterone and other hormones by the corpus luteum of pregnancy, so that the embryo can grow peacefully in the body. Patients with ectopic pregnancy have poorly developed trophoblast cells, which weakens the ability to secrete HCG. Drawing blood to check for beta-HCG is an important method for early diagnosis of ectopic pregnancy. Ectopic pregnancies have low β-HCG values on the first test, and some are close to normal pregnancies, i.e., there is a large overlap interval between the β-HCG of early ectopic and intrauterine pregnancies. For women undergoing assisted reproduction, blood is drawn for HCG value 12-14 days after ovulation is detected or after in vitro embryo transfer, and intrauterine pregnancy usually reaches 150-200 IU/L and above; if the blood is not drawn in advance and the β-HCG is low, ectopic pregnancy should be investigated. Women who are naturally pregnant and do not know the day of ovulation, such as those with irregular menstrual cycles, may have low HCG levels at 4 weeks after menopause due to delayed ovulation and delayed implantation of the embryo. Dynamic observation of HCG to watch for doubling becomes necessary. Beta-HCG doubling time in ectopic pregnancy takes 3-8 days, significantly less than the 1.4-2.1 days in normal pregnancy. Clinical review of blood values is often done after 2-3 days, and inadequate doubling should be used to screen for ectopic pregnancies, etc., but there are also reports in the literature of 48-h increases as low as 53% in normal intrauterine pregnancies. The gestational sac is usually visible on transvaginal ultrasound when the blood β-HCG reaches approximately 2500 IU/L (the threshold fluctuates between 1500-2500 IU/L depending on the testing organization). If no intrauterine gestational sac is seen, ectopic pregnancy should be highly suspected. False gestational sac can sometimes be seen in the uterus (meconium tubular pattern and blood formation), or ectopic pregnancy miscarriage resulting in the absence of gestational sac outside the uterus, which will increase the difficulty of diagnosis, and needs to be combined with the early dynamic observation of the situation, combined with the clinical symptoms, and further auxiliary examination, if necessary, to diagnose and treat. At the same time, the detection of progesterone decreased, CA-125 increased, etc. also has a certain reference value. Ectopic pregnancy occurs for many reasons, maternal, embryonic and male factors will affect the pregnancy outcome. The important thing is early detection and treatment to avoid risks.