Understanding Bleeding During Pregnancy: Causes & Flow Patterns

Vaginal bleeding during pregnancy affects 15–25% of women. While often benign, it can signal serious complications. Characterizing the flow pattern helps triage urgency, but all bleeding requires clinician assessment.

Flow Patterns & Typical Associations

Pattern	Description	Common Causes	Urgency
Light Spotting	Few drops, pink/brown, only on wiping	Implantation, cervical ectropion, post-coital, exam, hormonal	Contact provider same day
Light Bleeding	Pantyliner changes, <1 pad/hr	Subchorionic hematoma, threatened miscarriage, cervical polyp	Same day
Moderate Bleeding	1 pad/1–3 hrs, like light period	Threatened miscarriage, placental abruption (early), infection	Urgent (hours)
Heavy Bleeding	≥1 pad/hr, clots, saturating	Miscarriage, abruption, previa, vasa previa	Emergency
Intermittent	On/off over days/weeks	Hormonal, cervical, subchorionic hematoma, marginal previa	Scheduled eval
Continuous	Steady without stopping	Abruption, previa, cervical insufficiency, molar pregnancy	Emergency

Trimester-Specific Considerations

• First: Implantation, miscarriage, ectopic, molar, cervical.
• Second: Placenta previa, abruption, cervical insufficiency, vasa previa.
• Third: Bloody show (labor), previa, abruption, vasa previa.

Immediate Steps

1. Call your OB-GYN/midwife — describe amount, color, clots, pain, gestational age.
2. Use a pad (not tampon/cup) to quantify.
3. Save passed tissue if possible.
4. Rh-negative? Need RhIg within 72h of any bleeding >spotting.

Diagnostic Workup

• Quantitative hCG (serial).
• Transvaginal/transabdominal ultrasound.
• Speculum exam (cervical source).
• Fetal monitoring (if viable).

Never self-diagnose. Even light spotting deserves a call. Timely evaluation distinguishes reassuring causes from emergencies.