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