Use this tool to interpret a subchorionic hematoma in early pregnancy based on gestational age and size of the sac. It gives an educational risk band, context, and when to seek care.
How this estimate works
- Baseline by gestational age: early weeks have higher background risk which falls as the pregnancy advances, consistent with guideline summaries of early pregnancy loss risk after heartbeat confirmation and with cohort data on first trimester outcomes (ACOG Practice Bulletin).
- Size bands as percent of sac: the calculator uses common bands <10%, 10 to 25%, 26 to 50%, >50%. Larger fractions are associated with higher odds of adverse outcomes in meta analyses and cohort studies (Tuuli et al., Obstet Gynecol 2011; Jauniaux et al., Ultrasound Obstet Gynecol 2013).
- Location factor: retroplacental or intraplacental hematomas are treated as higher risk than marginal or subchorionic at the edge, reflecting associations reported in reviews and clinical series (Jauniaux 2013).
- Other modifiers: maternal age, multiple gestation, bleeding today, and prior loss add small penalties to the band. These are educational nudges and do not replace clinical judgment (NICE NG126).
- Resolution by week: typical chances by 9, 10, and 12 weeks are adjusted by size band and location, acknowledging that most small hematomas identified early resolve with expectant management (NHS overview).
- Trend with time: the estimate steps down as gestational age increases if no new concerns arise, consistent with follow up observations in early pregnancy units (RCOG patient information).
Size conversion used in the tool
Percent of sac ≈ 100 × (hematoma maximum width ÷ gestational sac mean diameter). When only millimetres or centimetres are reported, this ratio produces a simple percent that aligns with how many services describe hematoma size relative to the sac in early gestation (Tuuli 2011).
Re scan timing
Early pregnancy services commonly review in about 7 to 14 days if symptoms persist or findings are uncertain. If bleeding is ongoing or heavy, earlier review is appropriate (NICE NG126; NHS overview).
Limitations
- Studies vary in definitions and measurement methods for large hematomas, and ultrasound technique can change measurements by a few millimetres.
- User entered measurements may not match radiology calculations. The percent of sac ratio is a simplification for education.
- Uncaptured factors such as medical history, medications, or assisted reproduction specifics can change risk and follow up plans.
- Tuuli et al., Obstet Gynecol 2011 – meta analysis relating subchorionic hematoma to pregnancy outcomes, including size effects.
- Jauniaux et al., Ultrasound Obstet Gynecol 2013 – review of hematoma types, locations, and outcome associations.
- NICE NG126: Ectopic pregnancy and miscarriage – triage, ultrasound timing, and follow up in early pregnancy units.
- ACOG Practice Bulletin: Early Pregnancy Loss – background on first trimester risk after heartbeat and management principles.
- NHS: Subchorionic haematoma – patient facing overview, symptoms, and when to seek care.
- RCOG: Bleeding and or pain in early pregnancy – safety advice and follow up expectations.
How to use this calculator
- Enter your gestational age in weeks and days.
- Enter hematoma size as a percent of the gestational sac. If you have mm or cm, use the converter in the calc.
- Tell the tool if you have bleeding today.
- Optional: add maternal age, twin status, location tag, and prior loss if your report mentions them.
- Read the risk band, the recommended re-scan window, and red-flag cues.
This tool is educational only. It does not diagnose or replace care. Seek urgent care for heavy bleeding, severe pain, dizziness, or fainting.
Frequently asked questions
What is a subchorionic hematoma?
A subchorionic hematoma is a collection of blood between the gestational sac and the uterus. It can occur in early pregnancy and may cause light or heavy bleeding.
Does hematoma size change risk?
Risk is often discussed in relation to the size of the hematoma compared with the gestational sac. Larger proportions can be associated with higher risk, while many small hematomas resolve.
Does bleeding today affect the result?
Active bleeding can matter for short-term monitoring. The tool asks about bleeding so results can include clearer guidance on when to re-scan and when to seek urgent care.
How soon should I re-scan?
Re-scan timing depends on gestational age, hematoma size, and symptoms. The result provides a suggested window that many clinics use to reassess growth and bleeding.
When should I seek urgent care?
Seek urgent care for heavy bleeding, severe or one-sided pain, passing large clots, dizziness, or fainting. If unsure, contact your care team.