Three and a half weeks after a miscarriage, with an 8 mm endometrial thickness showing small Doppler flow, an empty uterus on ultrasound, and a serum β‑hCG of 6.2 IU/mL, should I undergo hysteroscopy to evaluate for retained products of conception?

You do not need hysteroscopy at this time—your clinical picture is consistent with normal post-miscarriage resolution

Based on your hCG of 6.2 IU/mL (essentially normalized), empty uterus on ultrasound, and timeline of 3.5 weeks post-miscarriage, the bleeding you're experiencing is most likely either residual shedding or return of normal menses, not retained products of conception (RPOC). 1

Why Hysteroscopy Is Not Indicated Now

Your hCG Level Rules Out Active Trophoblastic Tissue

• An hCG of 6.2 IU/mL is essentially at the threshold of detection (<5 IU/mL is considered negative), which effectively excludes significant retained trophoblastic tissue. 1
• If substantial RPOC were present, your hCG would be plateauing at higher levels (typically >50-100 IU/mL) or rising, not declining to near-zero. 2, 1
• The pattern of hCG decline in complete miscarriage shows a rate of 60-84% decrease at 7 days depending on initial levels; your near-complete resolution at 3.5 weeks confirms appropriate clearance. 3

The 8mm Endometrial Thickness with Doppler Flow Is Not Diagnostic of RPOC

• An 8mm endometrial stripe with some vascularity on color Doppler does not definitively indicate retained tissue—this can represent normal post-miscarriage endometrial regeneration, blood clot, or early proliferative endometrium if you're resuming normal cycles. 2
• Doppler flow alone cannot distinguish between benign regenerating endometrium and pathologic tissue; it requires correlation with hCG trends and clinical symptoms. 2
• The "empty uterus" finding on your scan argues against significant RPOC, which would typically show an echogenic mass or heterogeneous material within the cavity. 1

Your Bleeding Pattern Is Consistent with Normal Post-Miscarriage Recovery

• Light spotting and bleeding for 3-4 weeks after miscarriage is common and expected as the endometrium regenerates and hCG normalizes. 1
• The "period-like" bleeding at 3.5 weeks likely represents either final shedding of residual decidua or the return of your first normal menstrual cycle, which can occur once hCG drops below 10-20 IU/mL. 1

What You Should Do Instead

Serial hCG Monitoring Is the Appropriate Next Step

• Repeat your serum hCG in 1 week to confirm it continues declining toward <5 IU/mL. 2, 1
• If hCG plateaus (four consecutive similar values over 3 weeks) or rises, that would trigger concern for gestational trophoblastic neoplasia (GTN) and warrant further evaluation. 2, 1
• Continue weekly hCG measurements until you have one confirmatory value <5 IU/mL, at which point you can be discharged from monitoring. 2, 1

When to Seek Immediate Evaluation

• Return immediately if you develop severe abdominal pain, heavy bleeding (soaking a pad per hour), fever >38°C, foul-smelling discharge, or hemodynamic instability (dizziness, syncope). 1
• These symptoms would suggest complications such as infection or hemorrhage requiring urgent intervention. 1

Hysteroscopy Would Be Indicated Only If:

• Your hCG plateaus or rises on serial measurements (suggesting GTN). 2, 1
• You develop persistent heavy bleeding with hemodynamic compromise despite conservative management. 2
• Your hCG fails to decline to <5 IU/mL after 6-8 weeks, suggesting retained tissue. 2, 1

Important Caveats

The 5.9% Risk of Missed Ectopic Pregnancy

• Approximately 6% of women with apparent complete miscarriage (history of heavy bleeding, empty uterus on scan) actually have an underlying ectopic pregnancy. 4
• This is why serial hCG monitoring is mandatory—a plateauing or rising hCG would unmask an ectopic that was missed on initial imaging. 4
• Your declining hCG to 6.2 IU/mL makes ectopic pregnancy extremely unlikely, but continue monitoring until <5 IU/mL to definitively exclude it. 4

Hysteroscopy Carries Procedural Risks

• Diagnostic hysteroscopy, while generally safe, carries risks of uterine perforation, hemorrhage, infection, and fluid overload—complications that are not justified when your clinical picture suggests normal resolution. 5, 6
• Performing hysteroscopy prematurely (when hCG is near-normal and ultrasound shows an empty uterus) would expose you to unnecessary procedural risk without diagnostic benefit. 5, 6

In summary: Continue serial hCG monitoring weekly until <5 IU/mL, expect your bleeding to resolve over the next 1-2 weeks as your endometrium stabilizes, and reserve hysteroscopy only if hCG plateaus/rises or you develop concerning symptoms. 2, 1, 4