Determining chorionicity and amnionicity in twin pregnancies: Pitfalls

Area of Science:

• Maternal-Fetal Medicine
• Reproductive Genetics
• Diagnostic Imaging

Background:

• Accurate determination of chorionicity and amnionicity is crucial in multiple pregnancies for optimal management.
• While sonographic accuracy approaches 100%, specific challenges can lead to misdiagnosis.

Purpose of the Study:

• To identify and describe potential pitfalls in the sonographic determination of chorionicity and amnionicity in multiple gestations.
• To enhance understanding of rare variations and sonographic ambiguities that challenge diagnostic accuracy.

Main Methods:

• Review of sonographic findings in multiple pregnancies.
• Analysis of cases with discrepant chorionicity or amnionicity assessments.
• Discussion of rare twinning types and their impact on diagnosis.

Main Results:

• Pitfalls in chorionicity include the disappearance of the twin peak sign, artifactual twin peaks, misinterpretation of intrauterine structures, bipartite placentas in monochorionic twins, and errors in fetal sex determination.
• Rare twinning types like dizygotic monochorionic and sesquizygotic twins present diagnostic challenges.
• Amnionicity determination pitfalls involve the lack of correlation with yolk sac number and failure to visualize the intertwin membrane.

Conclusions:

• Despite high overall accuracy, sonographic determination of chorionicity and amnionicity in multiple pregnancies requires awareness of potential pitfalls.
• Understanding these challenges is essential for accurate diagnosis and appropriate clinical management of multiple gestations.