Objective: To evaluate the potential of the first-trimester ultrasound (US) features for the detection of central nervous system (CNS) anomalies. Methods/Methodology: This is a prospective one-center three-year study. Unselected singleton pregnant women were examined using an extended first-trimester anomaly scan (FTAS) that included the CNS assessment: the calvaria shape, the septum (falx cerebri), the aspect of the lateral ventricles, the presence of the third ventricle and aqueduct of Sylvius (AS) and the posterior brain morphometry: the fourth ventricle, namely intracranial translucency (IT), brain stem/brain stem–occipital bone ratio (BS/BSOB) and cisterna magna (CM). The spine and underlying skin were also evaluated. The cases were also followed during the second and third trimesters of pregnancy and at delivery. FTAS efficiency to detect major CNS abnormalities was calculated. Results: We detected 17 cases with CNS major abnormalities in a population of 1943 first-trimester (FT) fetuses, including spina bifida with myelomeningocele, exencephaly-anencephaly, holoprosencephaly, hydrocephaly, cephalocele and Dandy-Walker malformation. The CNS features in the abnormal group are presented. In the second trimester (ST), we further diagnosed cases of corpus callosum agenesis, cerebellar hypoplasia, vein of Galen aneurysm and fetal infection features (ventriculomegaly, intraventricular bands, intraventricular cyst and hyperechoic foci), all declared normal at the FTAS. During the third trimester (TT) scan we identified a massive fetal cerebral haemorrhage absent at previous investigations. We report a detection rate of 72.7% of fetal brain anomalies in the FT using the proposed CNS parameters. The sensitivity of the examination protocol was 72.7%, and the specificity was 100%. Conclusion: A detailed FT CNS scan is feasible and efficient. The majority of cases of major CNS abnormalities can be detected early in pregnancy. The visualization rates of the CNS parameters in the FT are great with short, if any, additional investigation time. FT cerebral disorders such as haemorrhage or infections were missed in the FT even when an extended evaluation protocol was used.

Our communication presents a prenatally detected case with severe spinal defect detected in the first trimester of pregnancy, accompanied by a large skin-covered myelomeningocele but normal cranio-cerebral structural appearance.These findings suggest that in the first trimester, the extent of the spinal defect, the cerebrospinal fluid leakage to a large, but skin-covered, meningocele and fixation of the spinal cord at the lesion are not sufficient to determine downward hindbrain displacement and the development of secondary signs for open spina bifida.Therefore, we suggest a careful evaluation of the fetal cerebral features if a meningocele is detected. The presence of the skin covering the lesion may not be evident in the first trimester, but the absence of intracranial open spina bifida markers may indicate a ‘closed’ spinal defect, which generally associates a good neurological outcome. Also, studies aimed to investigate the accuracy of the intracranial features for open spina bifida detection should consider the possibility of ‘closed’ myelomeningoceles to avoid incorrect correlations.