Abnormal Beta HCG
Anne Kennedy, MD
DIFFERENTIAL DIAGNOSIS
Common
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Imprecise Menstrual Dates
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Multiple Gestations
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Ectopic Pregnancy
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Retained Products of Conception (RPOC)
Less Common
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Complete Hydatidiform Mole
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Trisomy 21
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Trisomy 18
Rare but Important
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Invasive Mole
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Choriocarcinoma
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Embryonic/Fetal Demise
ESSENTIAL INFORMATION
Helpful Clues for Common Diagnoses
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Imprecise Menstrual Dates
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Maternal serum screening provides numerical risk for certain conditions based on expected levels of certain hormones
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Levels reported as multiples of the median (MOM) for gestational age
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Incorrect menstrual data → incorrect gestational age assessment at time of blood draw → spurious ↑ or ↓ of levels
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All patients with abnormal serum screen should have ultrasound as next step
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Verify gestational age
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Look for sonographic signs of aneuploidy
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If dates are incorrect, risk often recalculated or test redrawn
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Multiple Gestations
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Maternal serum hormone levels are higher in multiple than singletons
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Greater amount of fetal tissue per gestational age week
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Ectopic Pregnancy
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Ectopic pregnancies are not normal pregnancies
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Beta hCG often lower than for corresponding gestational age (GA) in a normal early pregnancy
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Normal “doubling” of beta hCG every 48 hours in early pregnancy may not occur
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Tubal ectopic is commonest type
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No intrauterine pregnancy + tubal mass + echogenic cul-de-sac fluid
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Echogenic fluid in a pregnant patient has a 90% positive predictive value for ectopic pregnancy
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Look for ring-like mass separate from ovary
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May have yolk sac or embryonic pole with or without cardiac activity
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“Ring of fire”: Increased flow seen in trophoblastic tissue around ectopic
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Do not confuse with increased flow around corpus luteum
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Amorphous adnexal mass may be due to hematosalpinx or clot adherent to ruptured tube
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Pseudogestational sac sign
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Decidual cast surrounds fluid collection central in endometrial cavity
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Lacks double decidual sac sign of normal intrauterine pregnancy
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Retained Products of Conception (RPOC)
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Residual trophoblastic tissue continues to produce beta hCG
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Levels do not fall to 0 as expected
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If levels remain elevated > 4 months post delivery, consider persistent gestational trophoblastic neoplasia
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Solid, heterogeneous, echogenic mass in endometrial cavity
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Persistent, thickened endometrium
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Irregular interface between endometrium and myometrium
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May see high velocity, low resistance flow
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Helpful Clues for Less Common Diagnoses
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Complete Hydatidiform Mole
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No embryo or fetus
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Beta HCG markedly elevated
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Enlarged uterus with “swiss cheese” endometrium
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Heterogeneous, echogenic intrauterine mass
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Completely fills uterine cavity
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Individual cysts that vary in size can be seen
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Mass is vascular with high velocity, low impedance flow (mean resistive index of 0.55)
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Bilateral, complex theca lutein ovarian cysts in 25-50%
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Trisomy 21
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High beta hCG associated with low unconjugated estriol, alpha fetoprotein
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First trimester ultrasound findings
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Increased nuchal translucency, absent nasal bone, abnormal ductus venosus flow
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Second trimester ultrasound findings
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Increased nuchal fold, short femur/humerus, duodenal atresia, atrioventricular septal defect
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More minor finding include echogenic bowel, mild pyelectasis, mild ventriculomegaly, echogenic intracardiac focus
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Trisomy 18
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Low beta hCG associated with low unconjugated estriol, alpha fetoprotein
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Multiple anomalies, intrauterine growth restriction
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Helpful Clues for Rare Diagnoses
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Invasive Mole
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Echogenic, cystic mass filling uterus and invading into myometrium
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