'Choroid bar': easy-to-seek marker of normal posterior fossa at 12-14 weeks' gestation.

OBJECTIVES: Our objectives were: (1) to assess the visualization rate of the choroid bar in a consecutive series of 306 first-trimester scans; (2) to verify, in this cohort of fetuses, the normality of the posterior fossa later in pregnancy; and (3) to confirm the non-visualization of the choroid bar in a retrospective series of fetuses with posterior fossa malformations. METHODS: This study included a prospective and a retrospective series. The former comprised 306 fetuses undergoing routine obstetric ultrasound at our unit in both the first and second trimesters over a 6-month period, while the latter comprised 12 cases of posterior fossa malformations. In the prospective study, the presence of the choroid bar, which is defined as a visually continuous, homogeneously hyperechogenic, thick structure bridging the cisterna magna from side to side, was evaluated at the end of the first-trimester nuchal translucency scan. In the retrospective study, previously acquired three-dimensional volume datasets were processed in order to assess whether the choroid bar could be visualized in cases of open spinal dysraphisms and vermian cystic anomalies. In the prospective study, confirmation of a normal posterior fossa was based on the sonographic features of this anatomical region at the time of the second-trimester anomaly scan at 19-21 weeks' gestation, while, in the retrospective study, it was based on autopsy results, when available, or further direct imaging of the defect later in pregnancy. RESULTS: In the prospective study, the choroid bar could be visualized in all 306 fetuses, on transabdominal ultrasound in 287 (93.8%) cases and on transvaginal ultrasound in 19 (6.2%) cases. The choroid bar was displayed with a ventral/dorsal approach in 67 (21.9%) cases, with a lateral approach in 56 (18.3%) cases and with both in 183 (59.8%) cases. All 306 cases were confirmed to have a sonographically normal posterior fossa at 19-21 weeks. On the other hand, in the retrospective study, it was not possible to visualize the choroid bar in any of the fetuses with posterior fossa malformations. CONCLUSIONS: We have described a new sign, the choroid bar, consistent with a normal posterior fossa at 12-14 weeks' gestation. The choroid bar provides the option of screening for major abnormalities of the posterior fossa, since its absence raises suspicion of both open spinal dysraphisms and posterior fossa cystic malformations. At the same time, it is easy to visualize, as it can be seen with all lines of insonation. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

INDIAMAN-20 (INstant DIAgnosis of 20 Major ANomalies) protocol: application of IOTA diagnostic strategy to fetal anomalies.

OBJECTIVES: To compile a list of instant diagnoses of major fetal anomalies, and to present their sonographic descriptors and test them in a retrospective series of fetuses with congenital anomalies managed at our center. METHODS: The first step was to identify major anomalies that meet the following criteria: (1) can be diagnosed directly and unequivocally on the basis of a set of descriptors evident on a single sonographic view; (2) are among those more commonly diagnosed in utero; (3) represent major lethal or life-threatening malformations or anomalies for which no or only palliative surgery can be performed. For each of these anomalies, a sonographic descriptor was produced. The second step was to test the descriptors of the instant diagnoses in all cases with these anomalies evaluated since January 2000 in our Fetal Medicine Unit, retrieved from our electronic database. For each congenital anomaly-sonographic descriptor pair we then evaluated the presence vs absence of an unequivocal relationship between anomaly and descriptor, assessing: whether a particular descriptor in a set reference plane identified unequivocally the anomaly, i.e. the same descriptor could not be found in any other malformation; and whether a particular anomaly presented the corresponding descriptor in all cases. Finally, we evaluated whether the sonographic descriptors could be applied in all trimesters or only selectively, considering the natural history of the 20 instant diagnoses. RESULTS: Of the 20 instant diagnoses, five involved the central/peripheral nervous system (exencephaly/anencephaly, alobar/semilobar holoprosencephaly, cephalocele, open spinal dysraphism, complete agenesis of corpus callosum), five involved the heart (hypoplastic left heart syndrome, complete atrioventricular septal defect, severe Ebstein's anomaly, critical aortic stenosis, transposition of the great arteries), five involved the abdominal wall (left-sided congenital diaphragmatic hernia, exomphalos, gastroschisis, body-stalk anomaly) or gastrointestinal tract (duodenal atresia), and five involved the remaining systems (three urinary (autosomal recessive polycystic kidney disease, multicystic dysplastic kidney, lower urinary tract obstruction), two skeletal (transverse limb defect, radial ray defect)). All of the descriptors were found to identify unequivocally the related malformations, whereas four of the malformations were not associated with their reference descriptors in every case. For example, congenital diaphragmatic hernia (left-sided) presented without the stomach in the thorax in 42/93 (45.2%) cases. Due to the natural history of the condition, not all signs were recognizable in the first trimester, some becoming evident only from the second trimester onwards. CONCLUSION: We have defined sonographic descriptors that enable an unequivocal instant diagnosis for a list of 20 major congenital anomalies: the 'INDIAMAN-20' (INstant DIAgnosis of Major ANomalies) protocol. We believe that using this approach may facilitate focused training of less experienced operators and that it may be incorporated into artificial intelligence and deep learning protocols, further boosting the instant prenatal recognition of these lethal or life-threatening malformations. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal detection of congenital heart disease at 12-13 gestational weeks: detailed analysis of false-negative cases.

OBJECTIVES: To report on the early detection of congenital heart disease (CHD) in low- and high-risk populations managed at our hospital; and perform a detailed analysis of false-negative diagnoses, in order to derive possible recommendations on how to reduce their incidence. METHODS: This was a retrospective observational study analyzing cases which underwent an ultrasound examination at the end of the first trimester at the Fetal Medicine and Surgery Unit of Gaslini Children's Hospital, Genoa, Italy, in the period January 2015 to December 2021. The study population included both low-risk pregnancies that underwent standard first-trimester combined screening and high-risk ones referred to our unit because of a positive combined test or suspicion of fetal anomalies raised in a regional community hospital. For each case, the following variables were retrieved and analyzed: number of fetuses, maternal body mass index, gestational age at first-trimester screening, whether the pregnancy was low or high risk, nuchal translucency thickness (normal or > 99th  centile), type of CHD, associated extracardiac anomalies, karyotype and pregnancy outcome. For low-risk pregnancies, suspicion of CHD was also recorded. In low-risk cases, sonographic cardiac screening comprised evaluation of the four-chamber view (grayscale and color/power Doppler) and three-vessel-and-trachea view (color/power Doppler). High-risk cases underwent early fetal echocardiography. False-negative cases were categorized according to likely cause of the missed diagnosis, as follows: human factor; technical factor; acoustic-window factor. RESULTS: Gestational age at ultrasound ranged from 12 + 0 to 13 + 6 weeks (crown-rump length (CRL), 50.1-84.0 mm) in the low-risk group and from 11 + 5 to 13 + 6 weeks (CRL, 45.1-84.0 mm) in the high-risk group. Over the 7-year study period, 7080 pregnancies were evaluated in the first trimester. Of these, 6879 (7167 fetuses) were low-risk and 201 were high-risk cases. In the low-risk group, there were 30 fetuses with CHD (including 15 major and 15 minor CHD), yielding a prevalence of 4.2/1000 (2.1/1000 for major CHD). Nine of the 30 CHD cases were suspected at screening ultrasound (7/15 major CHD). Excluding cases in which the CHD would not be expected to be associated with a modification of the screening views and would therefore not be detectable on screening ultrasound, 7/12 cases of major CHD were detected, corresponding to a sensitivity of 58.3%. Among the 201 high-risk cases, there were 46 fetuses with CHD (including 44 major and two minor CHD), of which 43 were detected, corresponding to a sensitivity for early fetal echocardiography of 93.5%, or 97.7% if the two cases that were unlikely to be detectable on first-trimester screening were excluded. Analysis of the 11 (of 24) false-negative cases that would be expected to be picked up on screening views revealed that human error (image interpretation and/or scanning approach) was involved in all 11 cases and technical factors (excessive color priority (color-balance function) and/or incorrect plane alignment) were present in two. There was impairment of the acoustic window (associated with maternal obesity and/or twin gestation) as a cofactor in five of the 11 cases. CONCLUSIONS: The sensitivity for detection of major CHD of early cardiac screening in low-risk pregnancy is under 60%, partly due to the natural history of CHD and, it seems, partly relating to human error and technical issues with image quality. Factors associated with false-negative diagnoses may be categorized into three types: human error, technical factors and acoustic-window impairment. We recommend: appropriate assessment with fetal posterior spine; that sufficient time is spent on assessment of the fetal situs; and that color/power Doppler settings are adapted to the individual case. A lower threshold for referring doubtful cases for early fetal echocardiography should be adopted in cases of maternal obesity and in twin gestation. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Comparison of fetal and neonatal sonographic measurements of ventricular size in second- and third-trimester fetuses with or without ventriculomegaly: cross-sectional three-dimensional ultrasound study.

OBJECTIVES: To assess, in a population comprising normal fetuses and fetuses with primary or post-hemorrhagic ventriculomegaly, the reproducibility of measurement of neonatal ultrasound indices in the fetus and to compare the performance of various cut-offs of these parameters to diagnose ventriculomegaly and classify its severity. METHODS: This was a retrospective cross-sectional study including 182 singleton fetuses assessed by transvaginal neurosonography. The sample populations included 116 normal fetuses and 66 fetuses with primary (n = 56) or post-hemorrhagic (n = 10) ventriculomegaly. In all cases, the atrial width (AW) was measured according to standard protocols and the findings were compared with four sonographic indices developed in the neonate: the anterior horn width (AHW), the ventricular index (VI), the thalamo-occipital distance (TOD) and the fronto-occipital horn ratio (FOHR). Reproducibility of measurements was assessed using the intraclass correlation coefficient (ICC) and diagnostic accuracy of the neonatal indices was assessed against AW using areas under the receiver-operating-characteristics curves (AUC). RESULTS: The intra- and interoperator reproducibility of measurement of AW and the neonatal measurements was excellent, with ICCs > 0.99 for all measures. The association in the fetus of all four variables developed in the neonate with the degree of ventriculomegaly as defined by the AW was strong for severe ventriculomegaly (AW > 15.0 mm; all AUC > 0.95), whereas the separation of cases with mild ventriculomegaly (AW, 10.0-15.0 mm) from those with normal AW (< 10.0 mm) was less effective. CONCLUSIONS: When applied in the fetus, all four indices of ventriculomegaly developed in neonates (AHW, VI, TOD, FOHR) were associated strongly with fetal AW when the AW measurement indicated severe fetal ventriculomegaly. However, for mild ventriculomegaly, the association was weaker, probably due to the fact that, in the fetus, mild ventriculomegaly is not caused by obstruction of the ventricular system. Considering the similar performance of the four neonatal variables and the technical issues involved in determination of TOD and FOHR in the fetus, use of VI and AHW is preferred. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal diagnosis of rhombencephalosynapsis: neuroimaging features and severity of vermian anomaly.

OBJECTIVES: To describe the prenatal neuroimaging spectrum of rhombencephalosynapsis (RES) and criteria for its classification according to the severity of vermian anomaly. METHODS: In this multicenter retrospective study of fetuses with RES between 2002 and 2020, the medical records and brain ultrasound and magnetic resonance images were evaluated comprehensively to determine the severity of the vermian anomaly and the presence of associated brain findings. RES was classified, according to the pattern of vermian agenesis and the extent of the fusion of the hemispheres, as complete RES (complete absence of the vermis) or partial RES (further classified according to the part of the vermis that was missing and, consequently, the region of hemispheric fusion, as anterior, posterior, severe or mixed RES). Findings were compared between cases with complete and those with partial RES. RESULTS: Included in the study were 62 fetuses with a gestational age ranging between 12 and 37 weeks. Most had complete absence of the vermis (complete RES, 77.4% of cases), a 'round-shaped' cerebellum on axial views (72.6%) and a transverse cerebellar diameter (TCD) < 3rd centile (87.1%). Among the 22.6% of cases with partial RES, 6.5% were classified as severe partial, 6.5% as partial anterior, 8.1% as partial mixed and 1.6% as partial posterior. Half of these cases presented with normal or nearly normal cerebellar morphology and 28.5% had a TCD within the normal limits. Infratentorially, the fourth ventricle was abnormal in 88.7% of cases overall, and anomalies of the midbrain and pons were frequent (93.5% and 77.4%, respectively). Ventriculomegaly was observed in 80.6% of all cases, being more severe in cases with complete RES than in those with partial RES, with high rates of parenchymal and septal disruption. CONCLUSIONS: This study provides prenatal neuroimaging criteria for the diagnosis and classification of RES, and identification of related features, using ultrasound and magnetic resonance imaging. According to our findings, a diagnosis of RES should be considered in fetuses with a small TCD (severe cerebellar hypoplasia) and/or a round-shaped cerebellum on axial views, during the second or third trimester, especially when associated with ventriculomegaly. Partial RES is more common than previously thought, but presents an extreme diagnostic challenge, especially in cases with normal or nearly-normal cerebellar morphobiometric features. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Frontal lobe growth is impaired in fetuses with congenital heart disease.

OBJECTIVES: The primary objective of this study was to assess whether fetuses with congenital heart disease (CHD) have smaller frontal brain areas compared with normal controls. The secondary objective was to evaluate whether there are any differences in frontal brain area between cases with different types of CHD, grouped according to their impact on hemodynamics. METHODS: This was a retrospective cross-sectional study, including 421 normal fetuses and 101 fetuses with isolated CHD evaluated between 20 and 39 gestational weeks at our fetal medicine and surgery unit in the period January 2016-December 2019. The study group was subdivided, according to the CHD hemodynamics, as follows: (1) hypoplastic left heart syndrome and other forms of functionally univentricular heart defect; (2) transposition of the great arteries; (3) conotruncal defects and other CHDs with large shunts; (4) right ventricular outflow tract obstruction, without a hypoplastic right ventricle; (5) left outflow tract obstruction; (6) others. The transventricular axial view of the fetal head was used as the reference view, on which the frontal lobe anteroposterior diameter (FAPD) and the occipitofrontal diameter (OFD) were measured, assuming the former to be representative of the area of the frontal lobes. The FAPD/OFD ratio was then calculated as FAPD/OFD × 100. These two variables (FAPD and FAPD/OFD ratio) were then evaluated and compared between the study and control groups. Adjustment for gestational age, both via multiple linear regression and by using a-posteriori matching based on the propensity score, was employed. RESULTS: In normal fetuses, FAPD showed a linear positive correlation with gestational age. In fetuses with CHD, the FAPD was shorter than in normal fetuses from the 20th gestational week onwards, with the difference increasing after 30 gestational weeks. FAPD/OFD ratio was significantly smaller in fetuses with CHD than in normal fetuses (P < 0.0001) at all gestational ages, with no apparent differences among the various CHD categories, all of which had smaller FAPD/OFD ratio compared with controls. CONCLUSIONS: Fetuses with CHD have a shorter FAPD and a smaller FAPD/OFD ratio compared with normal fetuses. This impaired growth of the frontal area of the brain seems to occur in all types of CHD, regardless of their impact on hemodynamics. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.