Chorionic Bump: Definition and Management
A chorionic bump is a convex protrusion from the choriodecidual surface into the first-trimester gestational sac that appears on ultrasound as an irregular bulge, typically with a hypoechoic center and hyperechoic rim, without internal vascularity 1, 2.
Clinical Significance
The presence of a chorionic bump significantly increases the risk of first-trimester miscarriage, with clinical loss rates of approximately 24% compared to 13.6% in pregnancies without this finding 3. However, if the pregnancy continues beyond the first trimester, it typically results in full-term delivery without additional pregnancy complications 3.
Risk Stratification
The prognosis varies based on specific ultrasound characteristics:
- Early detection (<56 days gestation) carries worse prognosis 4
- Larger relative size (>40% of gestational sac diameter) increases risk of poor outcomes 4
- Multiple lesions are associated with higher miscarriage rates 4
- Single lesions detected later have better outcomes
The original case series reported live birth rates of less than 50% 5, though more recent large-scale data from IVF pregnancies confirms the 24% clinical loss rate 3.
Management Approach
Serial transvaginal ultrasound monitoring throughout the first trimester is essential for all cases with chorionic bumps 2, 5.
Monitoring Protocol
- Initial assessment: Document size, number of lesions, and gestational age at detection
- Follow-up imaging: Repeat ultrasound every 1-2 weeks through first trimester
- Look for evolution: Most bumps show changes typical of hematoma resolution over time 5
- Assess viability: Confirm fetal cardiac activity and appropriate growth parameters
Patient Counseling
Inform patients that:
- There is an approximately 24% risk of first-trimester miscarriage 3
- If pregnancy continues past first trimester, outcomes are generally favorable with no increased risk of preterm delivery, placental abruption, or other pregnancy complications 3
- The finding likely represents a small subchorionic hematoma that protrudes into the gestational sac 5
Clinical Context
The prevalence ranges from 0.33% to 0.7% in general populations 4, 5. Risk factors include:
- History of infertility treatments 5
- Previous intrauterine operations 4
- Adverse maternal obstetric history 4
Differential Considerations
While the ACR guidelines discuss subchorionic hematomas as crescentic avascular collections that occur in 18-22% of first-trimester pregnancies with bleeding 6, chorionic bumps are distinct entities—they are focal convex protrusions rather than crescentic collections. Recent evidence suggests subchorionic hematomas may not independently increase pregnancy loss risk 6, whereas chorionic bumps clearly do 3.
Common Pitfalls
- Do not dismiss the finding: Unlike simple subchorionic hematomas, chorionic bumps warrant specific counseling about increased miscarriage risk
- Avoid single assessment: Serial imaging is mandatory, not optional
- Do not over-intervene: No specific treatment exists; management is expectant with close monitoring
- Size alone is not predictive: While larger relative size worsens prognosis, even small bumps require follow-up 5