Acoustic Radiation Force Impulse Elastosonography of Placenta in Maternal Red Blood Cell Alloimmunization: a Preliminary and Descriptive Study

Abstract

Aims: Maternal red blood cell alloimmunization is an important cause of fetal morbidity and mortality in the perinatal period, despite well-organized prophylaxis programs. The objective of the study was to evaluate placental elasticity by using Acoustic Radiation Force Impulse (ARFI) in Rhesus (Rh) alloimmunized pregnant women with hydropic and nonhydropic fetuses and to compare those with healthy pregnant women. Material and methods: This case-control and descriptive study comprised twenty-eight healthy pregnant women, 14 Rh alloimmunized pregnant women with nonhydropic fetuses, and 16 Rh alloimmunized pregnant women with hydropic fetuses in the third trimester of pregnancy. Placental elasticity measurements were performed by ARFI elastosonography at the day of delivery. The maternal characteristics and neonatal outcomes of the patients were also noted. Results: The highest mean placental ARFI scores were observed in Rh alloimmunized pregnant women with hydropic fetuses (1.13 m/s) (p= 0.001). Healthy controls and Rh alloimmunized pregnant women with nonhydropic fetuses had similar mean placenta ARFI scores (0.84 m/s, 0.88 m/s, respectively) (p< 0.05). Conclusions: Based on the present findings, the placenta becomes stiffer in Rh alloimmunized pregnancies complicated with hydrops fetalis. The increased placental ARFI scores may be a supplemental marker for adverse pregnancy outcomes, additional to Doppler evaluation of middle cerebral artery. This data should be confirmed with a large sample size and prospective studies by using serial measurements of ARFI elastosonography in maternal red blood cell alloimmunization.