First-trimester fetal neurosonography: technique and diagnostic potential

Mapping Fetal Brain Development of 10 Weeks' Gestational Age with 9.4T Postmortem MRI and Histologic Sections

BACKGROUND AND PURPOSE

The 10th week of gestational age (GA) is a critical period for evaluating brain development, but there is limited knowledge regarding the specific characteristics at this GA. This study is to map the brain structures at 10 weeks' GA by using 9.4T MRI and histologic sections.

MATERIALS AND METHODS

Six fetal specimens with normal brain development were imaged by using 9.4T MRI, followed by sectioning and staining. The 3D reconstruction models and quantitative measurements were obtained with Amira software.

RESULTS

Four zones of the laminar organization were identified in T2-weighted MRIs, while 6 zones were delineated in the corresponding histologic sections, demonstrating a strong consistency between the two. The key structures, including the midline structures, choroid plexus, subcortical nuclei, ventricles, brainstem, and cerebellum, were clearly distinguishable with unique characteristics in both MRIs and histologic sections. The 3D visualization model effectively demonstrated the shape, spatial positions, and interrelationships of the early fetal brain structures, and their qualitative measurements were obtained. The lateral ventricles and choroid plexus constituted a substantial proportion, with the lateral ventricles accounting for 43.0% of the cerebral hemisphere and the choroid plexus comprising 41.2% of the lateral ventricles.

CONCLUSIONS

At 10 weeks' GA, the fetal brain is in an early developmental stage. The integration of 9.4T T2-weighted MRIs, 3D reconstruction, and histologic sections offers a comprehensive view of the early fetal brain's characteristics, providing valuable insights for clinicians and anatomists.

The impact of prenatal ultrasound screening on termination of pregnancy with and without feticide: a retrospective analysis

BACKGROUND

Provision and uptake of antenatal screening is nonuniform in Austria, as there is no national screening program. The aim of the study was to evaluate the influence of prenatal ultrasound screening methods on the time of diagnosis and therefore the rate of feticide in pregnancies with fetal malformations.

METHOD

Retrospective data analysis of terminations of pregnancies (TOP) with and without feticide due to fetal structural anomalies at a single tertiary care referral center in Austria between 2007 and 2020.

RESULTS

Over the study period, the number of TOPs increased overall, and a nonsignificant rise in the rate of feticide was observed. Women who underwent TOP without feticide significantly more often had first trimester screening; in particular, 588 (86%) cases compared to 121 (57%) with feticide (p < 0.001). Furthermore, in the subgroup of cases diagnosed after 20 weeks of pregnancy (WoP), a significant association between cases without a mid-trimester anomaly scan and TOP with feticide was found. Gestational age at diagnosis was influenced by the type of malformation and therefore the affected organ system.

CONCLUSION

First trimester screening is critical in early fetal assessment and preventing unnecessary late terminations and feticide. Mid-trimester anomaly scan further increases the early detection of fetal malformations, especially those that become apparent later in pregnancy. Consequently, comprehensive counselling regarding the benefits of prenatal ultrasound screening should be provided to all pregnant women.

Effectiveness and clinical impact of using deep learning for first-trimester fetal ultrasound image quality auditing

BACKGROUND

Regular auditing of ultrasound images is required to maintain quality; however, manual auditing is time-consuming and can be inconsistent. We therefore aimed to develop and validate an artificial intelligence-based image quality audit (AI-IQA) system to audit images from the four key planes used in first-trimester scanning.

METHODS

The AI-IQA system was developed based on the YOLOv7 structure detection network and a multi-branch image quality regression network using a large multicenter internal dataset. Clinical validation was performed using 567 cases scanned by four radiologists with different experience levels, of which 349 were performed without AI-IQA feedback (clinical test set 1) and 218 were performed after 2-3 rounds of AI-IQA feedback (clinical test set 2). The proportion of standard images obtained and detailed expert audit results were compared to verify whether AI-IQA could objectively and accurately provide feedback on deficiencies in nonstandard images to assist radiologists at different experience levels in improving image quality.

RESULTS

In the internal test set, the AI-IQA system achieved high average accuracy precision, recall and F1-score in auditing the overall plane quality (0.881, 0.833, 0.842 and 0.837, respectively) and structure quality (0.906, 0.861, 0.857 and 0.859, respectively). In clinical test sets 1 and 2, AI-IQA results showed strong consistency with expert assessment results, with the average Cohen's Kappa coefficient exceeding 0.8 for all four planes. In addition, following AI-IQA feedback, the proportion of standard images obtained by junior and mid-level radiologists increased by 7.7% and 5.1%, respectively. AI-IQA takes only 0.05 s to assess each image, while experts require more than 20 s (p < 0.001).

CONCLUSIONS

The proposed AI-IQA system proved to be a highly accurate and efficient method of automatically auditing first-trimester scanning image quality, providing precise and rapid key plane quality control. This tool can also assist radiologists with different levels of experience to improve the image quality.

Ultrasound features of congenital cytomegalovirus infection in the first trimester: A case report

BACKGROUND

Congenital cytomegalovirus (CMV) infection represents a significant public health concern as the most prevalent viral infection in newborns, potentially leading to severe neurological and developmental complications. The majority of cases are asymptomatic and remain undetected during pregnancy due to the absence of effective screening methods.

CASE SUMMARY

A 27-year-old primigravida presented for early pregnancy ultrasound, which revealed an atypical finding: A normal anechoic thalamus appearing hyperechoic on the mid-sagittal view of the fetal head. Subsequent ultrasound examinations during mid and late gestation demonstrated classic intracranial features suggestive of congenital CMV infection. Chromosomal karyotyping and microarray analysis of the fetus yielded no significant abnormalities. Following comprehensive prenatal counseling regarding potential adverse fetal outcomes, the patient elected to continue her pregnancy. She ultimately underwent cesarean delivery at 42 weeks gestation at another facility, resulting in the birth of a female neonate. At five months of age, the infant presented with epilepsy and significant growth and developmental delays.

CONCLUSION

Congenital CMV infection occurs during the first trimester may manifest as hyperechoic thalamus which can be revealed by ultrasound in the mid-saggital view of the fetal head. Future research should investigate the correlation between echogenic thalamus and developmental outcomes, as well as explore early screening techniques for suspected congenital CMV infection cases.

The Value of Nuchal Translucency (NT) Ultrasonography for Fetal Malformation Screening

BACKGROUND

Early detection of fetal malformations is crucial for timely intervention and management in obstetric care. Existing screening methods may have limitations, prompting the exploration of novel approaches to improve detection accuracy.

AIM

This retrospective study explores an efficient fetal malformation screening method, aiming to provide a reference for obstetric examination.

METHODS

A total of 511 puerperae who underwent standardized ultrasound examinations in our hospital's first trimester from December 2020 to August 2022 were enrolled. Ultrasound was used to detect the thickness of the nuchal translucency (NT) in all puerperae during prenatal examination. The clinical values of detection indices in maternal prenatal physical examination were analyzed.

RESULTS

A total of 511 puerperae were investigated, and 12 malformed fetuses were detected, presenting a fetal malformation rate of 2.35%, including 3 cases of head and neck hydrocele, 2 cases of megacystis, 3 cases of anencephaly, and 4 cases of omphalocele. Among 499 normal fetuses, NT thickness > 3.0 mm accounted for 3.41%, while among the 12 malformed fetuses screened, NT thickness > 3.0 mm accounted for 75.00%, and there was a statistical difference between the two groups (Chi-square = 124.374, P < 0.05). Using ultrasound for fetal malformation screening revealed that the fetus with NT thickness value above 3.0 mm performed better in ultrasound screening (>3.0: AUC of 0.904; >3.5: AUC of 0.928; >4.0: AUC of 0.944 vs. >2.0: AUC of 0.863; >2.5: AUC of 0.878).

CONCLUSION

The findings underscore the critical clinical significance of NT thickening as a promising ultrasound soft index for screening fetal malformations. Beyond aiding in clinical diagnosis and postpartum treatment, the potential applications of these findings hold immense practical value. They pave the way for enhanced prenatal and postnatal care practices, emphasizing the translation of research outcomes into tangible benefits for healthcare providers and expectant parents alike.

Detailed Analysis of Fetal Malformations of the Supratentorial Structures of the Brain in High-Risk Pregnancies at 12-14 Gestational Weeks by Transvaginal 3D Ultrasound Examination

Purpose   To detect sonographic abnormalities of the supratentorial structures of the brain - future cavum septum pellucidum, cavum velum interpositum, third ventricle, ganglionic eminence and thalamus/hypothalamus - in fetuses with a crown-rump length of 45-84 mm in high-risk pregnancies. Materials and Methods   This study presents the retrospective analysis of transvaginally recorded 3D volumes of the fetal brain of 64 fetuses whose mothers consulted our ambulatory department for fetomaternal medicine for organic and/or genetic changes of their fetuses at GW 12-14. For this study we selected fetuses with 3D volume blocks of the fetal brain at best sonographic quality enabling detailed analysis and measurement of the supratentorial brain structures to correlate the results with the results of genetic analysis, ultrasound controls in later weeks of pregnancy, and fetal outcome. Results   Of 44 fetuses with genetic changes and 20 fetuses with syndromic changes, structural brain changes were found in 27 fetuses, analyzed by correlating the brain structures with the recently published structures of the brain at gestational week 12-14 in early pregnancy, presenting new details of early pathological brain development - migration disorders, milder variants of holoprosencephaly (lobar, MIH), corpus callosum agenesis, for the first time in early pregnancy. Conclusion   Supratentorial defects of the brain can be detected and analyzed in GW 12-14 in detail by direct analysis of sonopathology and visualization of pathological measurements using transvaginal 3D sonography in high quality.

Prenatal assessment of brain malformations on neuroimaging: an expert panel review

Brain malformations represent a heterogeneous group of abnormalities of neural morphogenesis, often associated with aberrations of neuronal connectivity and brain volume. Prenatal detection of brain malformations requires a clear understanding of embryology and developmental morphology through the various stages of gestation. This expert panel review is written with the central aim of providing an easy-to-understand road map to improve prenatal detection and characterization of structural malformations based on the current understanding of normal and aberrant brain development. For every developmental stage, the utility of each available neuroimaging modality, including prenatal multiplanar neuro sonography, anatomical MRI and advanced MRI techniques, as well as further insights from post-mortem imaging, has been highlighted.

Overview of reproductive and pregnancy health principles and practice used by maternal-fetal medicine specialists for fetal-neonatal neurology consultants

Unique from other fetal anatomical systems, the central nervous system (CNS) starts development early in the embryonic period shortly after fertilization before most patients are even aware they are pregnant. Maturation throughout pregnancy involve complicated structural and functional changes, most likely below the resolution of testing to detect. During this time, the fetal CNS is susceptible to lesions that reflect trimester-specific adverse events. Neonatal neurological status with childhood sequelae can result from combinations of antenatal, peripartum and neonatal adverse events. Person-specific clinical management choices must consider the timing of multiple mechanisms that can alter neurodevelopment including genetic causes, aetiologies after conception as well as communicable and non-communicable conditions that result in anomalous or destructive brain lesions. The appearance of the fetal brain also changes significantly through gestation as different structures mature and the cerebral cortex in particular increases in size and complexity. Therefore, obstetrical imagers and maternal fetal medicine physicians need to be aware of the expected evolving appearances of the healthy fetal brain as the fetus advances in gestation. Often when fetal CNS pathology is detected or anticipated during pregnancy, there is understandably significant parental anxiety regarding the long-term implications of their child's neurodevelopmental prognosis. In these instances, Maternal Fetal Medicine specialists often collaborate with Pediatric Neurologists in the antenatal period regarding diagnoses that anticipate neonatal or later childhood neurologic sequelae. Potential adverse outcomes are discussed with prospective parents to be integrated into choices based on shared decisions.

Insights into neurosonographic indicators for prenatal diagnosis of fetal neurological anomalies and cortical development: A systematic review of the literature

BACKGROUND

Congenital defects of the central nervous system are the second cause of disability in childhood, representing up to 20 % of structural malformations diagnosed prenatally. The accurate prenatal diagnosis of fetal neurological anomalies and the assessment of cortical development are critical for early intervention and improved long-term outcomes. Neurosonography plays a vital role in this process, providing detailed insights into the structural and functional development of the fetal brain. This systematic review aims to synthesize current knowledge on neurosonographic indicators for prenatal diagnosis, with a special focus on cortical development and its impact in cases of fetal growth defects.

MATERIAL AND METHODS

We conducted a comprehensive search for primary literature in PubMed database were searched for English and Spanish-language, peer-reviewed literature published in the last 15 years. Additional articles were identified by scrutinizing others search platforms (Cochrane Library, UpToDate). Inclusion criteria were single pregnancy and no known feto-maternal pathologies at the beginning of the study.

RESULTS

Of the 361 published abstracts identified, 35 met criteria for inclusion. The review highlighted the importance of detailed neurosonographic assessments, including the evaluation of cerebral fissures such as the Sylvian fissure, parieto-occipital fissure, and calcarine fissure. Targeted ultrasound techniques were found to provide comprehensive insights comparable to fetal magnetic resonance imaging. We underscored the significant impact of intrauterine growth restriction on cortical development, with early intervention being crucial. Genetic and congenital infection screenings were emphasized as essential components of prenatal assessment.

CONCLUSION

The assessment of fetal brain maturation patterns according to gestational age allows us to rule out a delay in cortical development. The heterogeneity of methods and evaluable parameters in fetal neurodevelopment makes it necessary to standardize the evaluation of the main structures of interest both for screening and for the diagnosis of cortical development anomalies, even with the aim of trying to improve upgrade prognostic advice.

Detection Rate of Fetal Anomalies in Early Mid-Trimester Compared to Late Mid-Trimester Detailed Scans: Possible Implications for First-Trimester Sonography

Objective: A late mid-trimester fetal organ scan (lMTS) is recommended between 18 and 22 weeks of pregnancy. Evidence has been accumulating on the effectiveness of first-trimester anatomy scans. Early mid-trimester fetal scans (eMTSs; 14-17 weeks) may have the advantage of visualization of most organs, hence allowing earlier genetic assessment and decision making. Our aim is to examine the effectiveness of eMTSs in identifying fetal anomalies compared to lMTSs. Methods: A retrospective study was conducted based on data from the multidisciplinary prenatal diagnosis clinic in a tertiary center. During the study period (2011-2021), an out-of-pocket eMTS in a community setting was offered routinely to the general population. Women who had previously undergone an eMTS and were later assessed due to a fetal anomaly in our clinic were included in the study. The cohort was divided into two groups according to whether the anomaly had been detected during the eMTS. We then compared the groups for factors that may be associated with anomaly detection in eMTSs. We used t-tests and chi-square tests, for quantitative and qualitative variables, respectively, to determine variables related to eMTS anomaly detection, and logistic regression for multivariate analysis. Results: Of 1525 women assessed in our multidisciplinary clinic, 340 were included in the study. The anomaly detection rate of the eMTS compared to the lMTS was 59.1% The eMTS detection rates for specific organ systems were as follows: skeletal, 57%; cardiac, 52%; congenital anomalies of the kidneys and urinary tract (CAKUT), 44%; central nervous system, 32.4%; chest, 33%; and abdominal, 28%. In multivariate analysis, abnormal first-trimester screening (aOR 3.2; 95%CI 1.26-8.08) and multiple anomalies (aOR 1.86; 95%CI 1.02-3.37) were found to be associated with eMTS anomaly detection. Conclusions: The eMTS detection rate was nearly 60% and was most accurate in detecting skeletal, cardiac, and CAKUT anomalies. Since the eMTS was community-based, this rate likely reflects a "real-world" scenario. Our findings support consideration of performing an eMTS or first-trimester scan routinely for earlier diagnosis and decision making, as an adjunctive to lMTSs. Future studies will examine the cost-effectiveness of early scans.

Antenatal screening for fetal structural anomalies - Routine or targeted practice?

Antenatal screening with ultrasound identifies fetal structural anomalies in 3-6% of pregnancies. Identification of anomalies during pregnancy provides an opportunity for counselling, targeted imaging, genetic testing, fetal intervention and delivery planning. Ultrasound is the primary modality for imaging the fetus in pregnancy, but magnetic resonance imaging (MRI) is evolving as an adjunctive tool providing additional structural and functional information. Screening should start from the first trimester when more than 50% of severe defects can be detected. The mid-trimester ultrasound balances the benefits of increased fetal growth and development to improve detection rates, whilst still providing timely management options. A routine third trimester ultrasound may detect acquired anomalies or those missed earlier in pregnancy but may not be available in all settings. Targeted imaging by fetal medicine experts improves detection in high-risk pregnancies or when an anomaly has been detected, allowing accurate phenotyping, access to advanced genetic testing and expert counselling.

First-trimester ultrasound of the cerebral lateral ventricles in fetuses with open spina bifida: a retrospective cohort study

BACKGROUND

Beyond 18 weeks of gestation, an increased size of the fetal lateral ventricles is reported in most fetuses with open spina bifida. In the first trimester of pregnancy, the definition of ventriculomegaly is based on the ratio of the size of the choroid plexus to the size of the ventricular space or the entire fetal head. However, contrary to what is observed from the midtrimester of pregnancy, in most fetuses with open spina bifida at 11 to 13 weeks of gestation, the amount of fluid in the ventricular system seems to be reduced rather than increased.

OBJECTIVE

This study aimed to compare the biometry of the lateral ventricles at 11 0/7 to 13 6/7 weeks of gestation between normal fetuses and those with confirmed open spina bifida.

STUDY DESIGN

This was a retrospective cohort study that included all cases of isolated open spina bifida detected at 11 0/7 to 13 6/7 weeks of gestation over a period of 5 years and a group of structurally normal fetuses attending at our center over a period of 1 year for the aneuploidy screening as controls. Transventricular axial views of the fetal brain obtained from cases and controls were extracted from the archive for post hoc measurement of cerebral ventricles. The choroid plexus-to-lateral ventricle length ratio, sum of the choroid plexus-to-lateral ventricle area ratio, choroid plexus area-to-fetal head area ratio, and mean choroid plexus length-to-occipitofrontal diameter ratio were calculated for both groups. The measurements obtained from the 2 groups were compared, and the association between each parameter and open spina bifida was investigated.

RESULTS

A total of 10 fetuses with open spina bifida were compared with 358 controls. Compared with controls, fetuses with open spina bifida showed a significantly smaller size of the cerebral ventricle measurements, as expressed by larger values of choroid plexus-to-lateral ventricle area ratio (0.49 vs 0.72, respectively; P<.001), choroid plexus-to-lateral ventricle length ratio (0.70 vs 0.79, respectively; P<.001), choroid plexus area-to-fetal head area ratio (0.28 vs 0.33, respectively; P=.006), and choroid plexus length-to-occipitofrontal diameter ratio (0.52 vs 0.60, respectively; P<.001). The choroid plexus-to-lateral ventricle area ratio was found to be the most accurate predictor of open spina bifida, with an area under the curve of 0.88, a sensitivity of 90%, and a specificity of 82%.

CONCLUSION

At 11 0/7 to 13 6/7 weeks of gestation, open spina bifida is consistently associated with a reduced amount of fluid in the lateral cerebral ventricles of the fetus, as expressed by a significantly increased choroid plexus-to-lateral ventricle length ratio, choroid plexus-to-lateral ventricle area ratio, choroid plexus area-to-fetal head area ratio, and choroid plexus length-to-occipitofrontal diameter ratio.

Fetal neuroimaging applications for diagnosis and counseling of brain anomalies: Current practice and future diagnostic strategies

Advances in fetal brain neuroimaging, especially fetal neurosonography and brain magnetic resonance imaging (MRI), allow safe and accurate anatomical assessments of fetal brain structures that serve as a foundation for prenatal diagnosis and counseling regarding fetal brain anomalies. Fetal neurosonography strategically assesses fetal brain anomalies suspected by screening ultrasound. Fetal brain MRI has unique technological features that overcome the anatomical limits of smaller fetal brain size and the unpredictable variable of intrauterine motion artifact. Recent studies of fetal brain MRI provide evidence of improved diagnostic and prognostic accuracy, beginning with prenatal diagnosis. Despite technological advances over the last several decades, the combined use of different qualitative structural biomarkers has limitations in providing an accurate prognosis. Quantitative analyses of fetal brain MRIs offer measurable imaging biomarkers that will more accurately associate with clinical outcomes. First-trimester ultrasound opens new opportunities for risk assessment and fetal brain anomaly diagnosis at the earliest time in pregnancy. This review includes a case vignette to illustrate how fetal brain MRI results interpreted by the fetal neurologist can improve diagnostic perspectives. The strength and limitations of conventional ultrasound and fetal brain MRI will be compared with recent research advances in quantitative methods to better correlate fetal neuroimaging biomarkers of neuropathology to predict functional childhood deficits. Discussion of these fetal sonogram and brain MRI advances will highlight the need for further interdisciplinary collaboration using complementary skills to continue improving clinical decision-making following precision medicine principles.

Impact of choroid plexus size in prenatal diagnosis of normal and abnormal closure of fourth ventricle

OBJECTIVE

To assess the role of the choroid plexus (CP) of the fourth ventricle (4V) in fetuses with an open 4V and a normal cerebellar vermis.

METHODS

Two groups of patients were recruited in two fetal medicine referral centers. The prospectively collected control group included singleton pregnancies with a normal sonographic examination after first-trimester combined screening for chromosomal abnormalities and normal outcome, recruited in the period between 2019 and 2022. The study group was selected retrospectively by searching our databases to identify all cases with an isolated open 4V and normal anatomy and size of the cerebellar vermis. The inclusion criteria of the study group were: (1) gestational age between 20 and 22 weeks; (2) a brainstem-vermis angle ≥ 18° in the midsagittal plane with an otherwise normal cerebellum and vermis; (3) 4V-CP visible and seen separately from the vermis; (4) absence of other intra- and extracranial anomalies; and (5) available prenatal and/or postnatal magnetic resonance imaging (MRI) data.

RESULTS

In 169 cases of the control group, the 4V-CP was seen separately from the cerebellar vermis and was noticed to progressively fill the space caudal to the 4V, between the vermis and brainstem. From 12 to 22 weeks, the surface areas of the vermis and medial portion of the 4V-CP increased progressively with advancing gestation (P < 0.0001). Intra- and interobserver correlation analysis showed good reproducibility for the measurements. Among the cases with an open 4V and a normal vermis, it was retrospectively feasible to visualize the 4V-CP separately from the inferior part of the vermis in 41 fetuses. In five of these cases, the open 4V was due to a small CP. In all 41 fetuses, the diagnosis on MRI was isolated upward rotation of the cerebellar vermis, and no additional anomaly was found.

CONCLUSIONS

Closure of the 4V is dependent on the 4V-CP and not only the cerebellar vermis. In fact, a small CP may represent another cause of an open 4V. Therefore, separate visualization of the 4V-CP and cerebellar vermis is crucial to improve discrimination between the different causes of an open 4V at the anomaly scan and its clinical implications. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Development of the prosencephalic structures, ganglionic eminence, basal ganglia and thalamus at 11 + 3 to 13 + 6 gestational weeks on 3D transvaginal ultrasound including normative data

OBJECTIVES

To show the development of ganglionic eminence, basal ganglia and thalamus/hypothalamus in week 11 + 3 to 13 + 6 by transvaginal 3D ultrasound.

METHODS

To visualize the prosencephalic structures surrounding the 3rd ventricle, 285 three-dimensional ultrasound volume blocks from 402 fetuses examined were selected in a prospective transvaginal 3D study to compare ultrasound images of ganglionic eminence, basal ganglia, thalamus/hypothalamus with embryological sections. In addition, measurements of the described structures were made in 104 fetuses to quantify the embryological development.

RESULTS

The sonomorphologic characteristics of ganglionic eminence, basal ganglia and thalamus/hypothalamus are described in 71% of the fetuses examined. Measurements of the structures in 57% of the fetuses, show the following results: axGE ap = 0.17 + 0.112*CRL; axGE/I = 0.888 + 0.048*CRL; axGE/BG = 0.569 + 0.041*CRL; coGE/BG = 0.381 + 0.048*CRL; coTh lat = - 0.002 + 0.135*CRL; coTh/HyT = 3.68 + 0.059*CRL; co3.V lat = 0.54 + 0.008*CRL.

CONCLUSION

Transvaginal 3D neurosonography allows visualization and measurement of normal structures in the fetal prosencephalon at 11 + 3 to 13 + 6 weeks of gestation (GW) including details of ganglionic eminence (GE), basal ganglia (BG), and thalamus/hypothalamus (Th/HyT). Further scientific work is needed before using the results to decide on pathological changes in patients.

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

Fetal development is a critical phase in prenatal care, demanding the timely identification of anomalies in ultrasound images to safeguard the well-being of both the unborn child and the mother. Medical imaging has played a pivotal role in detecting fetal abnormalities and malformations. However, despite significant advances in ultrasound technology, the accurate identification of irregularities in prenatal images continues to pose considerable challenges, often necessitating substantial time and expertise from medical professionals. In this review, we go through recent developments in machine learning (ML) methods applied to fetal ultrasound images. Specifically, we focus on a range of ML algorithms employed in the context of fetal ultrasound, encompassing tasks such as image classification, object recognition, and segmentation. We highlight how these innovative approaches can enhance ultrasound-based fetal anomaly detection and provide insights for future research and clinical implementations. Furthermore, we emphasize the need for further research in this domain where future investigations can contribute to more effective ultrasound-based fetal anomaly detection.

First-trimester choroid-plexus-to-lateral-ventricle disproportion and prediction of subsequent ventriculomegaly

OBJECTIVE

Ventriculomegaly can be associated with long-term neurodevelopmental impairment. Prenatal diagnosis of ventriculomegaly is most commonly made at the routine second-trimester anomaly scan. The value of first-trimester ultrasound has expanded to early diagnosis and screening of fetal abnormalities. The objective of this study was to assess the predictive accuracy of first-trimester choroid-plexus-to-lateral-ventricle-or-head ratios for development of ventriculomegaly at a later gestational age.

METHODS

This was a case-control study of fetuses with isolated ventriculomegaly diagnosed after 16 weeks' gestation and a control group of normal fetuses (without ventriculomegaly). The exclusion criteria included aneuploidy, genetic syndrome and/or other brain abnormality. Stored two-dimensional first-trimester ultrasound images were analyzed blindly offline and fetal biometry was performed in the axial view of the fetal head. The ratios of choroid plexus area (PA) to lateral ventricular area (VA), choroid plexus length (PL) to lateral ventricular length (VL), choroid plexus diameter (PD) to lateral ventricular diameter (VD) and PA to biparietal diameter (BPD) were measured at 11 + 0 to 13 + 6 weeks' gestation. Intra- and interobserver variability of measurement of these fetal head biometric parameters at 11 + 0 to 13 + 6 weeks' gestation were assessed in 20 normal fetuses using intraclass correlation coefficients with 95% CI. The accuracy of first-trimester biometric measurements for prediction of ventriculomegaly was assessed using the area under the receiver-operating-characteristics curves (AUC).

RESULTS

The analysis included 683 singleton pregnancies, of which 102 fetuses were diagnosed with ventriculomegaly. Ventriculomegaly was mild in 86 (84.3%) cases and severe in the other 16 (15.7%). All first-trimester fetal choroid-plexus-to-lateral-ventricle/head ratios were significantly lower in cases with ventriculomegaly compared with controls (P < 0.001), with good inter- and intraobserver agreement (≥ 0.95) for the majority of the fetal head biometric parameters assessed. On adjusting for crown-rump length, optimism-adjusted AUC values obtained after cross-validation showed that both PL/VL ratio (AUC, 0.87 (95% CI, 0.73-0.98)) and PA/VA ratio (AUC, 0.90 (95% CI, 0.82-0.98)) had good predictive accuracy for severe ventriculomegaly. The PA/BPD ratio (AUC, 0.73 (95% CI, 0.54-0.90)) had modest predictive ability, which was significantly lower compared with that of the PA/VA ratio and PL/VL ratio (P = 0.003 and P = 0.001, respectively). The predictive accuracy of PD/VD ratio was low with an AUC of 0.65 (95% CI, 0.47-0.84). Optimism-adjusted AUC values obtained after cross-validation showed that PA/VA ratio offered the highest predictive accuracy for mild ventriculomegaly with an AUC of 0.84 (95% CI, 0.79-0.89), followed by PL/VL ratio (AUC, 0.82 (95% CI, 0.76-0.88)), PA/BPD ratio (AUC, 0.76 (95% CI, 0.69-0.82)) and PD/VD ratio (AUC, 0.75 (95% CI, 0.67-0.81)). Calibration plots showed that both PA/VA and PL/VL ratios had good calibration.

CONCLUSION

First-trimester prediction of ventriculomegaly using ratios of fetal choroid plexus to lateral ventricle/head appears promising. Future prospective studies are needed to validate the predictive accuracy of these ultrasound markers as a screening tool for ventriculomegaly. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Cat-Ear-Line: A Sonographic Sign of Cortical Development?

OBJECTIVES

Diagonal echogenic lines outside the lateral ventricle have often been observed in the anterior coronal planes of the normal fetal brain by neurosonography. We have observed abnormal shapes of these echogenic lines in cases of malformation of cortical development (MCD). We named the ultrasound finding "cat-ear-line" (CEL). This study aimed to examine how and when CEL develops in normal cases compared with MCD cases.

METHODS

We retrospectively examined the fetal brain volume dataset acquired through transvaginal 3D neurosonography of 575 control cases and 39 MCD cases from 2014 to 2020. We defined CEL as the hyperechogenic continuous lines through subplate (SP) and intermediate zone (IZ), pre-CEL as the lines that existed only within the SP, and abnormal CEL as a mass-like or mosaic shadow-like structure that existed across the SP and IZ. All fetuses in the MCD group had some neurosonographic abnormalities and were ultimately diagnosed with MCD.

RESULTS

The CEL was detected in 97.9% (369/377) of the control group from 19 to 30 weeks. The CEL visualization rate of the MCD group in the same period was 40.0% (14/35) which was significantly lower than that of the control group (P < .001).

CONCLUSIONS

From this study, it appears that the CEL is an ultrasound finding observed at and beyond 19 weeks in a normally developing fetus. In some MCD cases, pre-CEL at and beyond 19 weeks or abnormal CEL was observed. Maldeveloped CEL at mid-trimester may help identify cases at-risk of subsequent MCD.

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

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.

First-trimester ventriculomegaly in fetuses with callosal agenesis: Cause or association?

The sonographic findings in four fetuses presenting with ventriculomegaly at first-trimester ultrasound that were subsequently diagnosed as having agenesis of the corpus callosum (ACC) are described. The diagnosis of early ventriculomegaly was suspected subjectively by identification of increased cerebrospinal fluid within the lateral ventricles and confirmed by measuring choroid plexus-to-lateral ventricle length and area ratios. Subsequent scans revealed complete ACC in two cases and partial ACC in the other two. This report adds to the increasing evidence suggesting that first-trimester ventriculomegaly is a strong sonographic marker of underlying brain anomalies, including less evident malformations such as ACC. Detailed second-trimester fetal neurosonography in those women continuing their pregnancies should be performed.

Computational methods for the analysis of early-pregnancy brain ultrasonography: a systematic review

BACKGROUND

Early screening of the brain is becoming routine clinical practice. Currently, this screening is performed by manual measurements and visual analysis, which is time-consuming and prone to errors. Computational methods may support this screening. Hence, the aim of this systematic review is to gain insight into future research directions needed to bring automated early-pregnancy ultrasound analysis of the human brain to clinical practice.

METHODS

We searched PubMed (Medline ALL Ovid), EMBASE, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, and Google Scholar, from inception until June 2022. This study is registered in PROSPERO at CRD42020189888. Studies about computational methods for the analysis of human brain ultrasonography acquired before the 20th week of pregnancy were included. The key reported attributes were: level of automation, learning-based or not, the usage of clinical routine data depicting normal and abnormal brain development, public sharing of program source code and data, and analysis of the confounding factors.

FINDINGS

Our search identified 2575 studies, of which 55 were included. 76% used an automatic method, 62% a learning-based method, 45% used clinical routine data and in addition, for 13% the data depicted abnormal development. None of the studies shared publicly the program source code and only two studies shared the data. Finally, 35% did not analyse the influence of confounding factors.

INTERPRETATION

Our review showed an interest in automatic, learning-based methods. To bring these methods to clinical practice we recommend that studies: use routine clinical data depicting both normal and abnormal development, make their dataset and program source code publicly available, and be attentive to the influence of confounding factors. Introduction of automated computational methods for early-pregnancy brain ultrasonography will save valuable time during screening, and ultimately lead to better detection, treatment and prevention of neuro-developmental disorders.

FUNDING

The Erasmus MC Medical Research Advisor Committee (grant number: FB 379283).

Basic sonographic examination of the fetal brain at 11-13 weeks' gestation: Rationale for a simple and reliable four-step technique

The widespread incorporation of first-trimester scanning between 11 and 13 weeks' gestation has shifted from the screening of chromosomal abnormalities, mainly by measuring nuchal translucency thickness and visualization of the nasal bone, to a more detailed study of the fetal anatomy leading to early detection of several structural congenital anomalies. This goal can be improved by the routine and focused sonographic assessment of specific anatomic planes and the identification of distinctive landmarks that can help disclosing a particular, non-evident condition. In this article we present the basis for a basic, early examination of the fetal brain during screening using a four-step technique, which can be readily incorporated during the first-trimester scan. The technique includes the focused visualization of the cranial contour, choroid plexuses of the lateral ventricles and midline, aqueduct of Sylvius, brainstem, fourth ventricle, and the choroid plexus of the fourth ventricle. The rationale for this approach is presented and discussed.

Presentation of ventriculomegaly at 11-14 weeks of gestation: An analysis of longitudinal data

OBJECTIVES

The aim of this study was to examine the value of the sonographic measurements of the choroid plexus and the lateral ventricles at 11-14 gestational weeks in fetuses that had the diagnosis of second-trimester ventriculomegaly (VM) as a clinical reference.

METHODS

The standard axial plane used for biparietal diameter measurement from 2D stored images in the first trimester was used to calculate the ratio between the choroid plexus and lateral ventricle diameter (PDVDR), the choroid plexus and lateral ventricle length (PLVLR) and the choroid plexus and lateral ventricle area (PAVAR) in 100 normal and 15 fetuses diagnosed with second-trimester VM.

RESULTS

In fetuses with VM, the measurements of PDVDR, PLVLR and PAVAR were all significantly smaller compared to normal fetuses (p = < 0.001, <0.001, <0.01). Four out of seven cases with mild VM had measurements below the 5th percentile (57%). 75% of cases with moderate or severe VM had at least one measurement below the 5th percentile.

CONCLUSIONS

Since the axial plane of the fetal head is obtained in all first-trimester routine screenings, the measurements of PDVDR, PLVLR and PAVAR could easily be integrated into routine examinations for an early detection of VM.

First trimester examination of fetal anatomy: clinical practice guideline by the World Association of Perinatal Medicine (WAPM) and the Perinatal Medicine Foundation (PMF)

This recommendation document follows the mission of the World Association of Perinatal Medicine in collaboration with the Perinatal Medicine Foundation. We aim to bring together groups and individuals throughout the world for precise standardization to implement the ultrasound evaluation of the fetus in the first trimester of pregnancy and improve the early detection of anomalies and the clinical management of the pregnancy. The aim is to present a document that includes statements and recommendations on the standard evaluation of the fetal anatomy in the first trimester, based on quality evidence in the peer-reviewed literature as well as the experience of perinatal experts around the world.

Low torcular Herophili position and large brainstem-tentorium angle in fetuses with open spinal dysraphism at 11-13 weeks' gestation

OBJECTIVE

To evaluate whether in fetuses with open spina bifida (OSB) the tentorium can be seen to be displaced downwards and vertically oriented by the time of the 11-13-week scan and whether this is reflected in an alteration of the brainstem-tentorium (BST) angle.

METHODS

The study population was recruited between 2015 and 2020 from three fetal medicine referral centers and comprised a control group and a study group of pregnancies with OSB. The control group was recruited prospectively and included singleton pregnancies with a normal sonographic examination after first-trimester combined screening for chromosomal abnormalities and normal outcome. The study group was selected retrospectively and included all cases with OSB between 2015 and 2020. All cases underwent detailed ultrasound assessment at 11 + 0 to 13 + 6 weeks' gestation. The position of the torcular Herophili (TH) was identified in the midsagittal view of the fetal brain with the use of color Doppler and was considered as a proxy for the insertion of the tentorium on the fetal skull. The BST angle was calculated in the same view and was compared between the two groups.

RESULTS

Sixty normal fetuses were included in the control group and 22 fetuses with OSB in the study group. In both groups, the BST angle was found to be independent of gestational age or crown-rump length (P = 0.8815, R²  = 0.0003861 in the controls, and P = 0.2665, R²  = 0.00978 in the OSB group). The mean BST angle was 48.7 ± 7.8° in controls and 88.1 ± 1.18°, i.e. close to 90°, in fetuses with OSB. Comparison of BST-angle measurements between the control group and cases with OSB showed a statistically significant difference (P = 0.0153). In all fetuses with OSB, the downward displacement of the TH and tentorium was clearly visible at the 11-13-week scan.

CONCLUSIONS

In fetuses with OSB, the BST angle is significantly larger than in normal controls, with the tentorium being almost perpendicular to the brainstem. This sign confirms the inferior displacement of the tentorium cerebelli with respect to its normal insertion on the occipital clivus as early as the first trimester of pregnancy and is useful in the diagnosis of Chiari-II malformation at this early stage. In fetuses with OSB, the low position of the tentorium and TH is clearly visible, even subjectively, at the 11-13-week scan. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

WAPM-World Association of Perinatal Medicine Practice Guidelines: Fetal central nervous system examination

These practice guidelines follow the mission of the World Association of Perinatal Medicine in collaboration with the Perinatal Medicine Foundation, bringing together groups and individuals throughout the world, with the goal of improving the ultrasound assessment of the fetal Central Nervous System (CNS) anatomy. In fact, this document provides further guidance for healthcare practitioners for the evaluation of the fetal CNS during the mid-trimester ultrasound scan with the aim to increase the ability in evaluating normal fetal anatomy. Therefore, it is not intended to establish a legal standard of care. This document is based on consensus among perinatal experts throughout the world, and serves as a guideline for use in clinical practice.

Position of the choroid plexus of the fourth ventricle in first- and second-trimester fetuses: a novel approach to early diagnosis of cystic posterior fossa anomalies

OBJECTIVE

To describe the sonographic appearance and position of the choroid plexus of the fourth ventricle (4V-CP) between 12 and 21 weeks' gestation in normal fetuses and in fetuses with Dandy-Walker malformation (DWM) or Blake's pouch cyst (BPC).

METHODS

The study population comprised 90 prospectively recruited normal singleton pregnancies and 41 pregnancies identified retrospectively from our institutional database that had a suspected posterior fossa anomaly at 12-13 weeks' gestation based on the ultrasound finding of abnormal hindbrain spaces. In all cases the final diagnosis was confirmed by prenatal and/or postnatal magnetic resonance imaging or postmortem examination. All pregnancies underwent a detailed ultrasound assessment, including a dedicated examination of the posterior fossa, at 12-13 weeks, 15-16 weeks and 20-21 weeks of gestation. Two-dimensional ultrasound images of the midsagittal and coronal views of the brain through the posterior fontanelle and three-dimensional volume datasets were obtained. Multiplanar orthogonal image correlation with volume contrast imaging was used as the reference visualization mode. Two independent operators, blinded to the fetal outcome, were asked to classify the 4V-CP as visible or not visible in both normal and abnormal cases, and to assess if the 4V-CP was positioned inside or outside the cyst in fetuses with DWM and BPC.

RESULTS

Of the 41 fetuses with apparently isolated cystic posterior fossa anomaly in the first trimester, eight were diagnosed with DWM, 29 were diagnosed with BPC and four were found to be normal in the second trimester. The position of the 4V-CP differed between DWM, BPC and normal cases in the first- and second-trimester ultrasound examinations. In particular, in normal fetuses, no cyst was present and, in the midsagittal and coronal planes of the posterior fossa, the 4V-CP appeared as an echogenic oval-shaped structure located inside the 4V apparently attached to the cerebellar vermis. In fetuses with DWM, the 4V-CP was not visible in the midsagittal view because it was displaced inferolaterally by the cyst. In contrast, in the coronal view of the posterior brain, the 4V-CP was visualized in all cases with DWM at 12-13 weeks, with a moderate decrease in the visualization rate at 15-16 weeks (87.5%) and at 20-21 weeks (75%). In the coronal view, the 4V-CP was classified as being outside the cyst in all DWM cases at 12-13 weeks and in 87.5% and 75% of cases at 15-16 and 20-21 weeks, respectively. In fetuses with BPC, the 4V-CP was visualized in all cases in both the midsagittal and coronal views at 12-13 weeks and in 100% and 96.6% of cases, respectively, at 15-16 weeks. In the coronal view, the 4V-CP was classified as being inside the cyst in 28 (96.6%), 27 (93.1%) and 25 (86.2%) cases at 12-13, 15-16 and 20-21 weeks, respectively. The medial segment of the 4V-CP was visualized near the inferior part of the vermis.

CONCLUSIONS

Our study shows that longitudinal ultrasound assessment of the 4V-CP and its temporal changes from 12 to 21 weeks is feasible. The 4V-CP is located inside the cyst, just below the vermis, in BPC and outside the cyst, inferolaterally displaced and distant from the vermian margin, in DWM, consistent with the pathogenesis of the two conditions. The position of the 4V-CP is a useful sonographic marker that can help differentiate between DWM and BPC as early as in the first trimester of pregnancy. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.