Ultrasonographic placental edematous changes as predictive markers of unplanned preterm birth in post-Fontan pregnancies: A single-center observational study.

Aim: Fontan surgery is a palliative procedure commonly performed for functional single-ventricle heart diseases. Fontan circulation is characterized by elevated central venous pressure and low cardiac output. It causes placental hypoxia, which could lead to poor obstetric outcomes. During post-Fontan pregnancies, ultrasonography may detect abnormal appearance of the placenta. We have focused on higher incidences of unexpected onset of labor when this ultrasonographic finding is present. In this study, we aimed to investigate whether this finding could be an indicator of premature delivery before pre-scheduled dates in post-Fontan pregnancies.

Methods: During post-Fontan pregnancies, the placenta exhibits a mosaic pattern with areas of low and high echogenicity and unusually thick on ultrasonography. We refer to these changes as "ultrasonographic placental edematous changes." We retrospectively analyzed clinical charts and ultrasonograms for post-Fontan pregnancies between 2015 and 2022.

Results: Fifteen patients were included in this study. Ultrasonographic placental edematous changes in the placenta during pregnancy were detected in eight cases (53%). Six (75%) of these patients experienced unexpected premature labor. Two patients underwent vaginal delivery because of sudden onset of labor. Four patients underwent emergency cesarean sections. Two patients underwent planned preterm cesarean sections. In the seven pregnancies without placental edematous changes, all deliveries occurred on the pre-scheduled dates determined based on the maternal heart condition.

Conclusions: Pregnancies with ultrasonographic placental edematous changes have a higher risk of unexpected preterm delivery than those without these changes. Ultrasonographic placental edematous changes may serve as predictive markers for unplanned preterm births in post-Fontan pregnancies.