Chorangiopagus parasiticus twins

Area of Science:

• Obstetrics and Gynecology
• Fetal Medicine
• Reproductive Biology

Background:

• Chorangiopagus parasiticus twins (CAPP) represent the most frequent type of asymmetric monozygous twinning, occurring in approximately 1% of identical twin pregnancies.
• This condition arises from an abnormal asymmetric development during monozygous twinning.

Observation:

• The parasitic twin (CAPP twin) is characterized by significant edema, underdeveloped lower spine and pelvis, and incomplete abdominal viscera, lacking thoracic organs.
• The parasitic twin has no independent placental vascular supply; its vessels are connected to the co-twin's circulation via the placenta or umbilical cord.

Findings:

• CAPP twins survive by exploiting the circulatory system of the normally developed co-twin, a phenomenon giving rise to the term 'parasiticus'.
• The parasitic twin typically presents as a fluid-filled, edematous mass with rudimentary lower body structures and minimal internal organ development.

Implications:

• Early identification of CAPP twins via ultrasound, as early as 12 weeks gestation, is crucial for timely management and intervention.
• Understanding the vascular connections and developmental anomalies in CAPP twins informs prenatal diagnosis and potential therapeutic strategies.