Quantitative serum hCG levels are helpful in evaluating suspected ectopic pregnancy because the classical triad of abdominal pain, delayed menses, and vaginal bleeding occurs in less than 20% of cases. Most ectopic pregnancies produce sufficient amounts of hCG to test positive with urine pregnancy tests. A urine pregnancy test can confirm that a woman is pregnant much faster and cheaper than a serum quantitative hCG. Serum hCG quantitation can then be done to determine if a fetus is large enough to be visualized by ultrasound. Gestational sacs are visible by transvaginal ultrasonography when serum hCG levels equal or exceed 1600 mIU/mL. If the hCG level is this high and no sac is visible in the uterus, ectopic pregnancy is suspected. Quantitation of serum hCG levels in paired specimens drawn 48 hours apart can also be used to help diagnose ectopic pregnancy. Women with uncomplicated pregnancies increase their serum hCG levels at least 1.6 fold during this interval. Smaller increments are consistent with ectopic or complicated pregnancy.. iu/L. Reference Range. S HCG Non pregnant Female or Male < 4.0 iu/L. Test Usage. Human chorionic gonadotropin (hCG) is a glycoprotein secreted by the placenta during pregnancy that consists of an alpha and beta subunit. The alpha subunit is structurally similar to the alpha subunits of FSH, LH and TSH. The beta subunit is distinct for hCG. The . The most sensitive, accurate and reliable pregnancy test is a blood test for the presence of beta HCG (human chorionic gonadotropin), often just called beta. The HCG is produced by the embryo, and is the embryo's signal to the mother that pregnancy has occurred. Beta HCG levels vary according to the gestational age. In a non-pregnant woman .