Real world Chorionic bump experience

Chorionic bump

A chorionic bump is a focal convex protrusion from the chorionic wall into the gestational sac cavity, seen in the first trimester.

It appears as:

  • A bulge projecting into the sac
  • Often echogenic or mixed echogenic
  • No internal vascularity on Doppler
  • Usually adjacent to the chorionic/placental surface

It is most commonly detected between 6–11 weeks.

Pathophysiology

  • A localized hematoma within the developing chorion
  • Possibly due to failed implantation remodeling
  • Focal placental hemorrhage or infarction

Histopathology

  • Organized hematoma
  • Fibrin deposition

It is a contained chorionic hematoma protruding inward, not a fetal structure.

Incidence

Reported incidence:

  • ~0.4–0.7% of early pregnancy scans

It is detected more often.

Sonographic appearance

Typical features:

  • Round or oval protrusion
  • Projects into gestational sac
  • No Doppler flows
  • Usually, single
  • Yolk sac and embryo separate from it

Differential Diagnosis:

  • Subchorionic hematoma (which lies between chorion and uterine wall)
  • Placental mass
  • Molar change (very different pattern)

Association with miscarriage

  • Increased risk of first-trimester pregnancy loss
  • Miscarriage rates reported between 20–50% in some series
  • Risk higher if:
    • Multiple bumps
    • Large bump
    • Absent fetal cardiac activity
    • Small gestational sac

However, many pregnancies with a chorionic bump continue normally.

Why increased risk of miscarriage?

  • Abnormal placentation
  • Localized placental vascular compromise
  • Early implantation defect

Higher risk if:

  • Large bump (>10–15 mm)
  • Multiple bumps
  • Increasing size over serial scans

Small, isolated bumps with good cardiac activity have better prognosis.

If pregnancy continues beyond first trimester

If fetal heartbeat persists and pregnancy progresses beyond 12–14 weeks:

  • Prognosis improves significantly
  • Many go on to normal outcomes

However

  • Slightly higher risk of:
    • Fetal growth restriction
    • Preterm birth
    • Placental complications

Aneuploidy association?

No strong consistent link with chromosomal abnormalities.

It is generally considered a placental phenomenon rather than genetic.

“This is a small collection within the early placenta. It is associated with a somewhat increased risk of miscarriage in the first trimester, but many pregnancies with this finding continue normally.”

Favorable prognosis

  • Single bump
  • Small size
  • Strong fetal cardiac activity
  • Appropriate crown-rump growth
  • No subchorionic hematoma
  • No vaginal bleeding

Unfavorable prognosis

  • No cardiac activity
  • Slow CRL growth
  • Sac too small for embryo
  • Multiple bumps
  • Rapid increase in size
  • Heavy bleeding

Chorionic bump is:

  • Rare
  • Likely focal placental hematoma
  • Associated with increased early miscarriage risk
  • Not necessarily predictive of poor second-trimester outcome if pregnancy progresses

If viable embryo with normal growth and isolated single small chorionic bump:

→ Risk of miscarriage is increased compared to baseline

→ But majority of ongoing pregnancies beyond first trimester do well