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 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.
Methodology & sources
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: larger hematomas have been associated with higher risk in some cohorts, but studies use different grading methods (Heller et al., 2018). The exact bands used by this calculator are simplified PCC assumptions.
- 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.
- 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: the displayed resolution estimates are PCC planning assumptions based on size, location, and gestational age. Published studies do not provide a universal week-by-week resolution table for an individual pregnancy.
- 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 .
Size conversion used in the tool
Percent of sac ≈ 100 × (hematoma maximum width ÷ gestational sac mean diameter). This is a simplified PCC ratio, not a standard clinical formula. Ultrasound studies use several different grading approaches (Heller et al., 2018).
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.
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 – systematic review and meta-analysis of subchorionic hematoma and pregnancy outcomes.
- 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.
- RCOG: Bleeding and or pain in early pregnancy – safety advice and follow up expectations.
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.
Support if you have experienced a loss
Reading about miscarriage, stillbirth, or infant loss can be difficult. If you have experienced a loss, you do not have to use this calculator or read the statistics. You may find it more helpful to talk with your care team or a support organization.
In the United States, groups such as:
offer information and bereavement support. If you are elsewhere, your local health service or a pregnancy and baby loss charity may be able to guide you to support in your region.