The role of routine first-trimester ultrasound screening for central nervous system abnormalities: a longitudinal single-center study using an unselected cohort with 3-year experience

Abstract

Background To evaluate the role of a standardized first-trimester scan in screening different kinds of central nervous system malformations and to report a 3-year experience from a tertiary center using an unselected cohort. Methods This was a retrospective analysis of prospectively collected data from a single center evaluating first-trimester scans with predesigned standardized protocols performed between 1 May 2017 and 1 May 2020, involving 39,526 pregnancies. All pregnant women underwent a series of prenatal ultrasound scans at 11–14, 20–24, 28–34 and 34–38 weeks of gestation. Abnormalities were confirmed by magnetic resonance imaging, postmortem examination or trained ultrasound professionals. Pregnancy outcomes and some postnatal follow-up were obtained from maternity medical records and telephone calls. Results A total of 38,586 pregnancies included in the study. The detection rates of CNS anomalies by ultrasound in the first, second, third and late third trimester were 32%, 22%, 25%, and 16%, respectively. And there were 5% of CNS anomalies missed by prenatal ultrasound. In the first-trimester scan, we diagnosed all cases of exencephaly, anencephaly, alobar holoprosencephaly and meningoencephalocele, and some cases of posterior cranial fossa anomalies (20%), open spina bifida (67%), semilobar holoprosencephaly (75%) and severe ventriculomegaly (8%). Vein of Galen aneurysmal malformation, closed spina bifida, lobar holoprosencephaly, intracranial infection, arachnoid cyst, agenesis of the corpus callosum, cysts of the septum pellucidum and isolated absence of the septum pellucidum were never detected during the first trimester. The abortion rates of fetal CNS anomalies detected by first-trimester scan, second-trimester scan, and third- trimester scan were 96%, 84% and 14%, respectively. Conclusions The study showed that almost 1/3 of central nervous system anomalies were detected by the standard first-trimester scan and these cases were associated with a high rate of abortion. Early screening for fetal abnormalities gives parents more time for medical advice and safer abortion if needed. It is therefore recommended that some major CNS anomalies should be screened in the first trimester. The standardized anatomical protocol, consisting of four fetal brain planes, were recommended for routine first trimester ultrasound screening.

Dandy Walker variant with agenesis of corpus callosum diagnosed late prenatally by foetal ultrasound: a case report

“…Hu and colleagues in their cohort study found that detection rate of CNS anomalies in first, second, third and late third trimester were 32%, 22%, 25% and 16%, respectively. These statistics suggest a crucial role of routine USG scans for detection of foetal anomalies 9 . The IUSOG guidelines recommends a transabdominal examination to be performed in two planes in routine practice; the transventricular plane and the transcrebellar plane.…”

“…Leiroz et al 13 in a similar study report sensitivity and specificity of the scan to be 61.1% and 96.3%, respectively. These data suggest a good specificity but fair sensitivity.Hu et al 9 also suggest that 5% of CNS anomalies are missed even after routine ultrasound scans. Improvement on aforesaid parameters may help improve the sensitivity as well as specificity of ultrasound scan.…”

Enhancing Fetal Anomaly Detection in Ultrasonography Images: A Review of Machine Learning-Based Approaches

“…Currently, US is still the most commonly used method to initially examine the development of the fetal brain for any fetal anomalies during pregnancy. During the 18-to 21-week pregnancy period, US imaging is used to measure the cerebrum, midbrain, cerebellum, brainstem, and other regions of the brain as part of the screening for fetal abnormalities [113,114]. To detect fetal brain abnormalities, Sreelakshmy et al developed a model (ReU-Net) based on U-Net and ResNet for the segmentation of fetuses' cerebellum using 740 fetal brain US images [115].…”