After passing a gestational sac 25 days ago, I have had brown, pink and occasional red spotting; my beta‑human chorionic gonadotropin was 6 mIU/mL last week and endometrial thickness is 8 mm, and today I have bright red bleeding—does this represent a normal menstrual period or retained products of conception?

Most Likely Diagnosis: Normal Menstrual Period

Your bleeding today is most likely your first menstrual period after the miscarriage, not retained products of conception (RPOC). With an hCG of 6 mIU/mL (essentially negative) and an endometrial thickness of 8 mm, the clinical picture strongly favors normal post-miscarriage uterine healing rather than RPOC.

Why This Is Your Period, Not RPOC

hCG Level Excludes Active Trophoblastic Tissue

• An hCG of 6 mIU/mL is essentially at the threshold of detection and indicates near-complete resolution of pregnancy tissue 1
• Serial hCG monitoring should demonstrate progressive decline to undetectable levels following complete miscarriage, which confirms resolution of trophoblastic tissue 1
• Persistent or plateauing hCG levels would indicate residual trophoblastic tissue requiring further evaluation, but your level has appropriately declined 1

Endometrial Thickness Is Normal for Post-Miscarriage Healing

• Endometrial thickness up to 20-25 mm in the early post-miscarriage period is considered nonspecific; your measurement of 8 mm is well below this range and does not suggest RPOC 1
• The shedding of residual endometrial tissue at approximately 8 mm thickness is a normal component of uterine healing after miscarriage 1
• Ultrasound findings that raise suspicion for RPOC include an echogenic endometrial mass with Doppler-detected vascularity, focal endometrial thickening with blood flow, or a discrete identifiable mass—not uniform 8 mm thickness 1

Timeline Supports First Menses

• At 25 days post-miscarriage with near-zero hCG, the return of menstruation is physiologically expected 1
• Intermittent bleeding may arise from the placental implantation site as it remodels and heals after tissue expulsion 1
• Ongoing uterine involution involves gradual breakdown and expulsion of the endometrial lining, which can produce spotting for several weeks 1

What RPOC Would Look Like (And You Don't Have This)

Ultrasound Criteria for RPOC

• An echogenic endometrial mass with internal vascularity on Doppler imaging 1, 2
• Focal endometrial thickening accompanied by blood flow on Doppler, not diffuse uniform thickness 1, 2
• A discrete, identifiable mass rather than the uniform 8 mm stripe you have 1

hCG Pattern in RPOC

• Persistent elevation or plateauing of hCG despite passage of tissue 1, 2
• Your hCG has appropriately declined to near-zero, ruling this out 1

Warning Signs That Would Require Immediate Evaluation

Return to Emergency Care If You Experience:

• Heavy vaginal bleeding (soaking more than one pad per hour for ≥2 consecutive hours) 1
• Fever ≥38°C (100.4°F) or foul-smelling vaginal discharge suggesting endometritis 1
• Hemodynamic instability such as dizziness, syncope, or orthostatic symptoms 1
• Severe lower abdominal pain beyond typical menstrual cramping 2

Red Flags for Gestational Trophoblastic Disease (Rare but Important)

• Plateau of hCG over 3-4 consecutive weekly measurements 1
• Rising hCG >10% across three values within 2 weeks 1
• Persistence of detectable hCG for ≥6 months after pregnancy loss 1
• Given your hCG is 6 mIU/mL, this is not a concern for you currently 1

Recommended Management

No Intervention Needed

• Do not diagnose RPOC solely on an endometrial thickness <20 mm; your 8 mm stripe is normal after miscarriage 1
• Dilation and curettage should be reserved for cases with heavy bleeding requiring transfusion, confirmed vascular RPOC on Doppler, or persistent/rising hCG—none of which apply to you 1

Follow-Up Plan

• Allow this bleeding episode to complete naturally as your first post-miscarriage period 1
• No repeat hCG testing is necessary unless bleeding becomes excessive or you develop warning signs 1
• Expect your menstrual cycles to normalize over the next 1-3 months 1

Common Pitfall to Avoid

The most common error is misinterpreting normal post-miscarriage endometrial shedding as RPOC. Your combination of near-zero hCG (6 mIU/mL), normal endometrial thickness (8 mm), and appropriate timeline (25 days post-miscarriage) all point to physiologic healing and return of menses, not retained tissue 1. Unnecessary intervention with dilation and curettage in this setting would expose you to surgical risks without benefit 1.