P15.16: Sonographic measurements of fetal nuchal fold, cerebellum and cisterna magna, in normal fetuses at the early second trimester of pregnancy

Abstract

In an effort to determine the normal sizes and relationships between the cranial structures, we measured the nuchal fold (NF), transverse cerebellar diameter (TCD), and cisterna magna (CM) in normal fetuses in the early second trimester of pregnancy using transvaginal sonography. In this prospective study of uncomplicated pregnancies, the CM NF and TCD were measured. This was a part of early screening of malformation. The examination was preformed between 14–16 weeks' gestation. The TCD and the anteroposterior (AP) diameter of the CM and the NF were measured on the transcerebellar plane. In addition, we measured the biparietal diameters (BPDs). 197 parturient were evaluated. The mean age of the women was 33.28 ± 4.2 years (range, 18–38 years), and the mean gestational age of the fetuses was 15.01 ± 0.43 weeks (range, 14.14–16 weeks). The mean BPD was 29.01 ± 18.7 mm (range, 30–96 mm). The mean diameters of the CM and NF were 2.55 ± 1.63 mm, 2.03 ± 0.52 mm respectively, no correlation was found between the week and CM or NF (r = 0.05, p = 0.41), (r = − 0.03, p = 0.62) respectively. The mean TCD was 14.14 ± 1.22 mm and positively correlated with gestational week (r = 0.4, p < 0.0001). In normal fetuses, the cerebellum, NF and CM should be measured by ultrasound examination between 14 and 16 weeks' menstrual age. Because abnormalities in these cranial structures may be indicative of central nervous system malformations, the availability of mean sonographic measurements from normal fetuses should be helpful in determining the need for additional testing in fetuses with abnormal measurements.