Early Pregnancy Bleeding: Differentiating Implantation Bleeding from Menstruation and Pathology

Bleeding in early pregnancy is common (20–30%) but never "normal." Implantation bleeding is a diagnosis of exclusion.

Implantation Bleeding Characteristics

• Timing: 6–12 days post-ovulation (cycle day 20–26); before expected menses.
• Volume: Spotting only (few drops, pantyliner); never heavy.
• Color: Light pink, brown (oxidized); not bright red.
• Duration: Hours to 1–2 days.
• Symptoms: Mild cramping possible; no clots.

Menstrual Bleeding

• On time or slightly early/late; progressive heavy flow (days 1–3); bright to dark red; clots common; 4–7 days.

Differential Diagnosis

• Threatened/inevitable/complete miscarriage
• Ectopic pregnancy (pain + bleeding = emergency)
• Cervical ectropion/polyp (postcoital spotting)
• Subchorionic hematoma
• Gestational trophoblastic disease
• Infection (cervicitis, vaginitis)

Clinical Action

1. Quantitative hCG (serial 48h: viable IUP rises ≥53%; ectopic rises slower/plateaus).
2. Transvaginal ultrasound (discriminatory zone ~1500–2000 mIU/mL).
3. Rh typing; RhIg if negative.
4. Counsel on warning signs (pain, heavy bleed, dizziness).

Key Message

Any bleeding with positive pregnancy test warrants clinician evaluation. Do not self-diagnose as implantation bleeding.