How should I interpret serum hCG levels in a patient with suspected ectopic pregnancy, and what follow-up is recommended?

Interpretation of serum hCG levels in suspected ectopic pregnancy:

• Serum hCG levels should not be used alone to determine the location of the pregnancy, as they cannot reliably distinguish ectopic from intrauterine pregnancies.
• In women with a pregnancy of unknown location (PUL), clinical symptoms take precedence over hCG levels for assessment.
• Two serum hCG measurements should be taken approximately 48 hours apart to assess the trend in hCG levels, which helps guide management.
• An increase in serum hCG greater than 63% over 48 hours suggests a likely developing intrauterine pregnancy, but ectopic pregnancy cannot be excluded; a transvaginal ultrasound scan is recommended between 7 and 14 days later, or earlier if hCG ≥1500 IU/L.
• A decrease in serum hCG greater than 50% over 48 hours suggests the pregnancy is unlikely to continue; a urine pregnancy test should be done 14 days after the second hCG test to confirm resolution.
• If hCG levels decrease less than 50% or increase less than 63%, urgent clinical review within 24 hours is required.

Follow-up investigations:

• Transvaginal ultrasound is the diagnostic tool of choice to locate the pregnancy and assess for ectopic pregnancy.
• Repeat transvaginal scans and serial hCG measurements may be used to confirm diagnosis if initial imaging is inconclusive.
• Laparoscopy may be considered if diagnosis remains uncertain or if clinical condition deteriorates.

Management recommendations based on hCG levels and clinical findings:

• Expectant management may be appropriate for clinically stable, pain-free women with declining hCG levels (drop ≥15% on days 2, 4, and 7) and no signs of rupture.
• Methotrexate medical management is offered to women with unruptured ectopic pregnancy, serum hCG <1500 IU/L, adnexal mass <35 mm, no visible heartbeat, no intrauterine pregnancy, and ability to return for follow-up.
• Surgical management is indicated for women with significant pain, adnexal mass ≥35 mm, visible fetal heartbeat, serum hCG ≥5000 IU/L, or inability to follow up after methotrexate.
• Women treated with methotrexate require serial hCG monitoring on days 4 and 7 post-treatment, then weekly until hCG is negative; plateau or rising hCG warrants reassessment.
• Women undergoing surgery should have hCG monitored weekly until negative; anti-D immunoglobulin is offered to rhesus-negative women after surgical management.

Women with PUL or ectopic pregnancy should be given written information on symptoms warranting urgent review and access to emergency care 24/7.

Future pregnancies should be reported early to arrange early ultrasound to confirm location and viability.

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