OC23.01: Reference data representative of normal findings at 2D and 3D gray scale ultrasound examination of the cervix from 17 to 41 gestational weeks

Abstract

Background: Fetoscopic laser coagulation of the vascular anastomoses is currently the best available treatment method for severe twin–twin-transfusion syndrome (TTTS) diagnosed < 26 weeks. However, postoperative single intrauterine fetal death (sIUFD) commonly occurs, in which unequal placental distribution may play an important role. Objectives: To evaluate the use of preoperative Magnetic Resonance Imaging (MRI) to determine placental volume distribution and to correlate unequal placental distribution with the occurrence of postoperative sIUFD. Material and methods: Preoperative MRI (T1-T2-Diffusion) of the monochorionic placenta was performed in 28 cases of TTTS to determine the placental volume ratios. Placental distribution was considered to be unequal when the placental volume ratios were less than 30/70. An ultrasound scan was performed 24 and 48 hours after the procedure to check fetal viability. Postoperative sIUFD was defined as demise of 1 twin within 48 hours. After birth, volumetric CT angiography was performed of 9 placentas with double survivors. The placental volume ratios measured on postnatal CT angiography were compared with the predicted values on preoperative MRI. Results: Determination of the placental volume ratios was possible in 22/28 (79%) of cases on T2-weighted MRI as well as on ADC maps. In 8/9 placentas examined after birth, preoperative MRI had accurately predicted the placental distribution. In 3/4 cases with predicted unequal placental distribution, sIUFD occurred, of which 2 fetuses had the largest placental part and 1 had the smallest part. In contrast, sIUFD occurred in only 3/18 cases (17%) with equal placental distribution (P < 0.05). Conclusion: Preoperative MRI seems to accurately predict placental volume distribution in most cases with TTTS. Also, unequal placental distribution appears to be a risk factor for sIUFD after laser treatment. However, sIUFD was not restricted to the fetus with the smallest placental part.