The Role of Placental Anastomoses in Severe Brain Injury After Fetal Demise in Monochorionic Twins: A Multicenter Retrospective Study.

BACKGROUND: Monochorionic twins share a single placenta with vascular anastomoses including arterio-arterial and veno-venous anastomoses, which are low-resistance, superficial, and bidirectional anastomoses. Following single fetal demise, the survivor is at risk of brain injury due to acute exsanguination through arterio-arterial and veno-venous anastomoses into the low-pressure circulation of the deceased co-twin. OBJECTIVE: To assess whether the number and diameter of arterio-arterial and veno-venous anastomoses are associated with severe brain injury in the survivor following single fetal demise. The secondary objective was to evaluate the placental angioarchitecture and to identify potential additional placental risk factors for severe brain injury in monochorionic twin pregnancies after fetal demise. STUDY DESIGN: Multicenter retrospective study including all monochorionic twin dye-injected placentas of pregnancies with spontaneous single or double fetal demise. Pregnancies were excluded in case of twin anemia polycythemia sequence, selective feticide, and demise following laser surgery for twin-twin transfusion syndrome. A potential association between the number and diameter of arterio-arterial and veno-venous anastomoses and the presence of severe brain injury was assessed using univariable logistic regression analyses corrected for multiple testing (q-values). RESULTS: A total of 75 placentas of monochorionic twin pregnancies were included in the analysis, including 43 cases of single fetal demise and 32 cases of double fetal demise. Severe brain injury occurred in 25% (19/75) of pregnancies. In the overall cohort, arterio-arterial and veno-venous anastomoses were present in 89% (17/19) and 68% (13/19) of placentas from twins with severe brain injury, compared to 77% (43/56) and 46% (26/56) without severe brain injury, respectively. Placentas of twins with severe brain injury showed larger diameter of the arterio-arterial anastomoses (mean 2.5 mm; 95% confidence interval, 1.7-3.3 vs 1.6 mm; 95% confidence interval, 1.2-2.0; P<.01), and larger veno-venous anastomoses (mean 3.0 mm; 95% confidence interval, 1.6-4.5 vs 1.5 mm; 95% confidence interval, .9-2.1; P=.02). The total number of arterio-arterial and/or veno-venous anastomoses (median 2 vs 1; P<.01) and their cumulative total diameter (mean 5.8 mm; 95% confidence interval, 3.9-7.7 vs 3.1 mm; 95% confidence interval, 2.1-4.0; P<.01) were also larger in the pregnancies with severe brain injury. Discordant insertions were more common in pregnancies with severe brain injury (47% vs 20%; P=.03). In logistic regression, diameter of the arterio-arterial (odds ratio, 1.58; 95% confidence interval, 1.11-2.26; q=.02), the presence of veno-venous anastomoses (odds ratio 3.47; 95% confidence interval, 1.10-10.96; q=.04), diameter of the veno-venous (odds ratio 1.36; 95% confidence interval, 1.09-1.69; q=.01), and total diameter of arterio-arterial and veno-venous anastomoses (odds ratio 1.27; 95% confidence interval, 1.09-1.48; q=.01) were associated with severe brain injury in the survivor after fetal demise. In analyses restricted to survivors after single fetal demise only no significant associations were found. CONCLUSION: In this exploratory analysis, severe brain injury after single or double fetal demise is associated with presence and number of veno-venous anastomoses, and diameter of the arterio-arterial and veno-venous anastomoses. In analyses restricted to single fetal demise, no significant associations were observed, likely due to limited statistical power.