The absolute value of serum HCG varies greatly between different periods of pregnancy and between pregnant women, generally non-pregnant women have blood HCG <100 IU/L. Serum HCG levels during pregnancy are shown below.
Gestational weeks HCG (IU/L)
0.2-1 5-50
1-2 50-500
2-3 100-5000
3-4 500-10000
4-5 1000-50,000
5-6 10,000-100,000
6-8 15000-200000
2-3 10,000-100,000
During the first 3 months of pregnancy, HCG levels approximately double every (2.2 ± 0.5) days.
Serial blood HCG measurements should be done in patients with suspected ectopic pregnancy, and an abnormal pregnancy should be considered if the blood HCG rises <50% at 48-hour intervals.
Blood HCG levels are lower in 85% of patients with ectopic pregnancy than in patients with intrauterine pregnancy of the same gestational age. 2.5% of patients with normal intrauterine pregnancy have blood HCG levels below the 95% normal limit. Blood HCG levels are also lower in patients with spontaneous abortion at all stages. The three blood HCG levels overlap.
The doubling time of blood HCG in normal early intrauterine pregnancy is 1.4-2.2 days, while the doubling time of blood HCG in abnormal pregnancy (ectopic pregnancy, miscarriage) is 3-8 days.
In general, the positive predictive value of a normal rise in HCG to rule out ectopic pregnancy is about 95%. Ectopic pregnancy can also be estimated by comparing ultrasound findings with HCG concentrations. Intrauterine gestational sacs should be identified by vaginal ultrasound when HCG reaches 1000 U/L and must reach 6500 U/L for abdominal ultrasound to identify intrauterine gestational sacs, if this is not the case, ectopic pregnancy should be suspected.
Clinical significance.
1, diagnosis of early pregnancy blood hCG quantitative immunoassay concentration >251,t/L is defined as positive for pregnancy; suspicious between 5-251u/L. Using enzyme-linked immunosorbent assay (ELISA) to determine hCG, the sensitivity is generally between 20-501u/L, which is the level of hCG about 10 days after conception, so it is used for early pregnancy diagnosis quickly, easily and inexpensively than blood concentration determination. At present, the commonly used diagnostic test strip for early pregnancy, namely monoclonal antibody early pregnancy test, can detect the lowest amount of hCG in urine as 251u/L.
2.Estimating the prognosis of pre-eclampsia when the urinary hCG drops to 6251u/L or the hCG concentration is measured every 2-3 days, if it does not rise exponentially, then miscarriage is inevitable and birth control treatment can be unnecessary.
3.Diagnosis of ectopic pregnancy In ectopic pregnancy, the hCG value is often lower than normal. If the B-hCG value is not exponentially increasing and there are no signs of intrauterine pregnancy on ultrasonography, ectopic pregnancy should be highly suspected. If the blood B-hCG value is <1001u/l, rupture of ectopic pregnancy rarely occurs.
4, diagnosis and condition monitoring of trophoblastic tumor hCG blood concentration often exceeds 100,0001u/L in case of gravida. If hCG maintains high concentration after the third trimester and does not fall, it suggests gravida; after removal of gravid fetal masses, hCG should show a substantial decrease and fall to negative level at 16 weeks after removal. If the decrease is slow or rises after the decrease, or if it does not turn negative at 16 weeks, it is a sign of erosive staphyloma. hCG decrease is consistent with the outcome of treatment for erosive staphyloma. In choriocarcinoma, the hCG level can be very high and is often used for diagnosis and detection of the disease and treatment effect.
5.Supportive diagnosis and disease monitoring of other tumors Some tumors can secrete hCG, such as choriocarcinoma of hypothalamus or pineal germ cells, ovarian choriocarcinoma, teratoma, ovarian asexual cell tumor, etc. The detection of blood hCG level is not only beneficial to diagnosis, but also important for disease monitoring. In addition, the blood hCG level of patients with hepatocellular carcinoma, intestinal cancer, liver cancer, lung cancer, pancreatic cancer and gastric cancer can also be increased to a certain extent, which should be noted during clinical diagnosis.