When do human chorionic gonadotropin (hCG) levels decrease after a missed miscarriage?

hCG Decline After Missed Miscarriage

After a missed miscarriage, hCG levels typically decrease by approximately 70% within 3 days and by over 90% within 5 days of the pregnancy loss. 1, 2

Normal hCG Decline Pattern

• Most standard urine pregnancy tests (sensitivity of 20-25 mIU/mL) will become negative within 2 weeks after a miscarriage 3
• The rate of hCG decline follows a predictable pattern:
  • Day 3 after miscarriage: Mean decline of 70.0% ± 10.6% (range 36.9-98.6%) 2
  • Day 5 after miscarriage: Mean decline of 91.4% ± 4.4% (range 68.4-97.7%) 2
  • Days 7-9 after miscarriage: Mean decline of 97.1% ± 1.7% (range 92.4-99.2%) 2
  • Days 10-14 after miscarriage: Mean decline of 98.5-98.7% 2

Factors Affecting hCG Clearance

• The rate of hCG decline is not significantly affected by:
  • Initial hCG level before the miscarriage 2
  • Gestational duration (up to 63 days) 2
• However, higher initial hCG concentrations tend to show a more rapid rate of decline 4

Clinical Significance of hCG Patterns

• A decline in hCG of less than 21% at 2 days or less than 60% at 7 days after miscarriage may suggest:

  • Retained products of conception
  • Incomplete miscarriage
  • Possible ectopic pregnancy 4

• For complete miscarriage, the expected decline in serum hCG is approximately:

  • 48-66% within 24 hours 5
  • 60-84% at 7 days (depending on initial hCG value) 4

Warning Signs Requiring Medical Attention

• Plateaued or rising hCG levels after an initial decline may indicate:

  • Retained products of conception requiring further intervention 3
  • In rare cases, development of gestational trophoblastic disease (especially after molar pregnancy) 6, 7

• If hCG levels plateau (defined as <15% change over 48 hours) for two consecutive measurements, further evaluation is needed 7

Practical Applications

• Healthcare providers can be reasonably certain that a woman is not pregnant if she is ≤7 days after a spontaneous or induced abortion 3
• For women who require confirmation of complete abortion sooner than 1 week, a single repeat hCG on Day 5 may be clinically useful due to the predictable decline pattern 2
• After molar pregnancy, more prolonged hCG follow-up is required (up to 6 months) due to risk of gestational trophoblastic neoplasia 7, 6

Monitoring Recommendations

• For routine miscarriage: A repeat hCG test at 2 weeks is usually sufficient to confirm appropriate decline 3
• For cases with clinical concerns: Serial measurements every 48 hours until a clear declining pattern is established 7
• For suspected retained products: Ultrasound evaluation in addition to hCG monitoring 3