Characterisation of deep arterio-venous anastomoses within monochorionic placentae by vascular casting

Area of Science:

• Fetal Medicine
• Placental Anatomy
• Vascular Biology

Background:

• Monochorionic (MC) placentae feature vascular connections between fetuses.
• Arterio-venous anastomoses (AVA) are crucial for placental sharing.
• Accurate characterization of MC placental vasculature is vital for managing twin complications.

Purpose of the Study:

• To characterize arterio-venous anastomoses (AVA) in monochorionic (MC) placentae.
• To determine if shared cotyledons involve co-termination of vessels on the chorionic plate.
• To assess the detectability of all AVA by visual inspection of the chorionic plate.

Main Methods:

• Vascular casting of 15 MC placentae.
• Comparison of visually suspected typical AVA with those identified post-casting.
• Classification of atypical AVA based on their anatomical characteristics.

Main Results:

• Only 49% of suspected typical AVA were confirmed post-casting.
• Atypical AVA were found in over 90% of MC placentae.
• Type I and Type II atypical AVA were present in 53% and 73% of placentae, respectively.

Conclusions:

• Shared cotyledons in MC placentae are not always characterized by visible co-termination of vessels.
• Deep anastomoses beneath the chorionic plate are common and not detectable by surface inspection.
• These findings have significant implications for the efficacy and targeting of laser treatment for twin-twin transfusion syndrome.