Beta-human chorionic gonadotropin (β-hCG) is a specific pregnancy hormone synthesized by trophoblast cells after embryo implantation.
- Detectable in blood 6–8 days post-fertilization, making it one of the earliest markers of pregnancy.
- In urine, β-hCG reaches detectable levels1–2 days after appearing in plasma, which is why urine pregnancy tests are slightly less sensitive than blood tests.
Role of Beta-hCG in Pregnancy
- During the first trimester, β-hCG maintains corpus luteum function, ensuring the production of progesterone and estrogens.
- This process continues until the placenta fully takes over hormone production.
- In male fetuses, β-hCG stimulates Leydig cells to produce testosterone, which is essential for male reproductive development.
- Peak β-hCG levels occur around 10–11 weeks of pregnancy, then gradually decline.
- In multiple pregnancies, β-hCG levels are proportionally higher due to the presence of multiple embryos.
- The test is performed on a venous blood sample.
- Fasting (8–14 hours) is required, but water intake is allowed.
- The test can also be taken 4 hours after a light meal.
- Avoid physical and emotional stress, as well as alcohol, before testing.
In Women:
- Amenorrhea (absence of menstruation)
- Early pregnancy detection
- Suspected ectopic pregnancy
- Pregnancy monitoring (hCG dynamics)
- Diagnosis of trophoblastic diseases (e.g., choriocarcinoma, hydatidiform mole)
- Monitoring the effectiveness of treatment for trophoblastic diseases
- Prenatal screening for fetal abnormalities
In Men:
- Differential diagnosis of testicular tumors
Causes of Increased Beta-hCG Levels
In Men and Non-Pregnant Women:
- Choriocarcinoma (gestational trophoblastic disease)
- Seminoma (testicular cancer)
- Testicular teratoma
- hCG-producing gastrointestinal tumors
- Recent abortion (hCG remains elevated for 4–5 days after termination)
- hCG medication use (e.g., in fertility treatments)
In Pregnant Women:
- Multiple pregnancy
- Mismatch between expected and actual gestational age
- Severe pregnancy toxicosis or preeclampsia
- Maternal diabetes
- Chromosomal abnormalities in the fetus (e.g., Down syndrome, Edwards syndrome)
- Synthetic progestin use
Causes of Decreased Beta-hCG Levels
In Pregnant Women:
- Lower-than-expected β-hCG levels (delayed rise or insufficient increase of more than 50%)
- Ectopic pregnancy
- Missed miscarriage (early pregnancy loss)
- Risk of spontaneous abortion (miscarriage)
- Chronic placental insufficiency
- Intrauterine fetal death (2nd or 3rd trimester)
False-Negative Beta-hCG Results (No Detectable Increase During Pregnancy)
- Test performed too early (before β-hCG reaches detectable levels in blood/urine)
- Ectopic pregnancy (hCG levels rise slower than in normal pregnancy)