Fetal Advanced Neurosonography in the First Trimester of Pregnancy

Some of the central nervous system malformations (CNSs) can be detected or suspected during the first trimester.

Prospective observational study including singleton pregnancies, CRL between 60 and 82 mm and normal basic ultrasound examination. In the axial plane, we examined: lateral ventricles (LV), choroid plexus of LV (PCVL), PCVL/VL ratio, insula, cerebellum, distance from Sylvian aqueduct to occipital bone, IV ventricle (IVV), and cisterna magna (CM) and in the sagittal plane, we assessed: 4 lines-3 spaces, brain stem (BS), fourth ventricle, IVV choroid plexus (PC), CM, distance from BS to occipital bone (BSOB) and BS/BSOB ratio.

Ninety-two fetuses were included. The extended examination was successfully performed in 86 (93.5%) cases. The insula, LV and CPLV (axial planes) as well as all structures in the sagittal planes were assessed at 100%. The IVV, PC and CM (axial planes) were visualized at 90 (97.8%) fetuses. In 89 (96.7%) fetuses, the cerebellum was successfully evaluated, while in 88 (95.7%) cases, the tectum, aqueduct of Sylvius, and Ac-Oc distance were measured. Good intra- and interobserver concordance was observed for all parameters, as confirmed by Bland-Altman analyses. Advanced ultrasound increased the total examination time by 3 min compared to basic examination.

Advanced first-trimester CNS assessment, including the incorporation of early markers to predict CNS abnormalities, is feasible with good intra- and interobserver agreement and minimal additional ultrasound scanning time.