Abnormal development of the vasculosyncytial membrane in early pregnancy failure.

Objective: To investigate chorionic villous vasculogenesis (maturation) and development of the vasculosyncytial membrane (margination) using CD34 immunohistochemistry.

Design: Case-control study.

Setting: Microscopic analysis of first trimester chorionic villi.

Patient(s): Twelve patients with anembryonic pregnancies, 12 with embryonic death, and 12 with terminated normal pregnancies.

Intervention(s): Quantitative analysis of chorionic villi blinded to group and gestational age using CD34 immunohistochemistry.

Main Outcome Measure(s): Vascular parameters (mean functional vascular area, vessels with a lumen, and hemangiogenetic cords, peripherally or centrally located).

Result(s): Terminated normal pregnancies show significantly more vessels per chorionic villus (maturation) (mean +/- SEM) in comparison with embryonic deaths and anembryonic pregnancies (5.3 +/- 0.3 vs. 1.4 +/- 0.2 and 0.7 +/- 0.1), located mainly peripherally (margination) (3.0 +/- 0.2 vs. 0.9 +/- 0.2 and 0.2 +/- 0.0). Anembryonic pregnancies show significantly more centrally located cords in comparison with embryonic deaths and termination of pregnancies (3.3 +/- 0.2 vs. 2.7 +/- 0.2 and 1.5 +/- 0.1).

Conclusion(s): A defective chorionic villous vascularization, demonstrating inadequate vasculogenesis and abnormal development of the vasculosyncytial membrane, is seen in pregnancies complicated by embryonic death and is even more pronounced in anembryonic pregnancies. Initiation of placental vasculogenesis is a basic feature in all types of pregnancy and is subsequently modulated directly or indirectly by embryonic signaling.