Is a beta human chorionic gonadotropin (beta hCG) level of 220, with transvaginal ultrasound findings of an empty uterus and no free fluid, indicative of an ectopic pregnancy in a female of reproductive age with no known significant medical history?

β-hCG of 220 with Empty Uterus: Diagnostic Approach

A β-hCG of 220 mIU/mL with an empty uterus and no free fluid does NOT definitively indicate ectopic pregnancy—this represents a pregnancy of unknown location (PUL) requiring serial β-hCG monitoring every 48 hours and close follow-up, as ectopic pregnancy cannot be excluded or confirmed based on these findings alone. 1

Why This Is Not Definitively Ectopic

• At β-hCG 220 mIU/mL, you are well below the discriminatory threshold (1,500-3,000 mIU/mL) where an intrauterine gestational sac should be visible on transvaginal ultrasound 1, 2
• This level is too low to expect visualization of any pregnancy—either intrauterine or ectopic—on ultrasound 2
• Transvaginal ultrasound has only 33% sensitivity for detecting intrauterine pregnancy and 25% sensitivity for detecting ectopic pregnancy when β-hCG is below 1,500 mIU/mL 3
• The absence of free fluid is reassuring, as it suggests no rupture has occurred 4

What This Clinical Picture Represents

This is classified as a pregnancy of unknown location (PUL), which has three possible outcomes: 1

• 36-69% will be normal early intrauterine pregnancies that are simply too early to visualize 2
• 7-20% will ultimately be diagnosed as ectopic pregnancy 1, 2
• The remainder will be failing/nonviable intrauterine pregnancies 1

Critical Management Algorithm

Immediate actions: 1

1. Obtain specialty consultation or arrange close outpatient follow-up for all patients with indeterminate ultrasound 1
2. Schedule repeat quantitative β-hCG in exactly 48 hours to assess for appropriate rise or fall 1
3. Do not initiate any treatment based solely on this initial β-hCG level—follow-up is essential 1, 2

Interpreting the 48-hour β-hCG: 1

• Viable intrauterine pregnancy: β-hCG typically doubles (rises 53-66%) every 48-72 hours 1
• Nonviable pregnancy: β-hCG fails to rise appropriately or decreases 1
• Abnormal pregnancy requiring immediate evaluation: β-hCG plateaus (<15% change) or rises >10% but <53% for two consecutive measurements 1

When to repeat ultrasound: 1

• Continue serial β-hCG measurements every 48 hours until levels reach 1,500-2,000 mIU/mL 1
• Repeat transvaginal ultrasound when β-hCG reaches the discriminatory threshold 1
• At that point, absence of intrauterine gestational sac becomes highly concerning for ectopic pregnancy 2

Critical Red Flags Requiring Emergency Evaluation

Instruct the patient to return immediately if: 2

• Severe or worsening abdominal pain (especially unilateral) 2
• Shoulder pain (suggests hemoperitoneum from rupture) 2
• Heavy vaginal bleeding 2
• Dizziness, syncope, or signs of hemodynamic instability 2

Important Caveats

• Never use a single β-hCG value to exclude ectopic pregnancy in patients with indeterminate ultrasound 1
• Approximately 22% of ectopic pregnancies present with β-hCG levels below 1,000 mIU/mL, and 50% present below 1,500 mIU/mL 3, 5
• 44% of ruptured ectopic pregnancies had β-hCG levels less than 1,500 mIU/mL at presentation 5
• Use the same laboratory for all serial measurements, as different assays have varying sensitivities 1, 2
• Document all findings carefully, as the diagnosis will evolve over time 1, 2

Risk Stratification Context

• Patients with β-hCG >2,000 mIU/mL and no visible intrauterine pregnancy have a likelihood ratio of 19 for ectopic pregnancy 1
• At your patient's level of 220 mIU/mL, the risk is substantially lower but cannot be quantified without serial measurements 1
• The absence of free fluid reduces immediate rupture risk but does not exclude ectopic pregnancy 4, 5