Necrotizing Enterocolitis in Multi Fetal Pregnancies: Can We Find a Key in Placental Abnormalities? A Retrospective Data Analysis

Objective: We aimed to evaluate the relationship between chorionicity, placental abnormalities and necrotizing enterocolitis in multiple pregnancies. We hypothesized that unbalanced interfetal transfusion through vascular anastomoses in monochorionic placentation causes hypoperfusion of the intestinal mucosa, increasing the risk of developing necrotizing enterocolitis. Material and methods: All women with multiple pregnancies who delivered at the University Medical Center Utrecht between January 1995 and December 2015 were retrospectively selected. We compared baseline characteristics and neonatal and maternal outcomes. Secondly, we analyzed ultrasound and placental pathology findings of monochorionic multiples with and without necrotizing enterocolitis. Finally, we compared illness characteristics of necrotizing enterocolitis in monochorionic multiples with necrotizing enterocolitis in dichorionic multiples. Results: We included 2859 dichorionic and 817 monochorionic neonates. Necrotizing enterocolitis occurred significantly more often in monochorionic as compared to dichorionic neonates (3.3% and 1.6% respectively), also after correction for birthweight, gestational age and nulliparity (OR 1.7, 95% CI 1.0 - 2.8). Ultrasound abnormalities were not associated with necrotizing enterocolitis. Histopathology showed that necrotizing enterocolitis was significantly associated with the presence of unbalanced interfetal transfusion (76.9% of monochorionic with necrotizing enterocolitis versus 31.4% of cases without necrotizing enterocolitis, P = 0.001). Conclusion: Necrotizing enterocolitis is more common in monochorionic multiples as compared to dichorionic multiples, at least in part due to the presence of and related to the presence of unbalanced interfetal transfusion through arterial-venous anastomoses in the placenta. Possibly, subtle ischemic damage caused by intra-uterine fetal hypotension or anemia plays a key role in the development of necrotizing enterocolitis in monochorionic twins.