We present a case of transposition of great arteries (TGA) diagnosed prenatally using HDlive Flow with spatiotemporal image correlation (STIC) at 20 weeks and 5 days of gestation. Right-sided stomach was noted on routine second-trimester screening. Ventricular septal defect, pericardial effusion, and parallel arrangement of great arteries were identified using two-dimensional fetal echocardiography and color Doppler. HDlive Flow with STIC clearly showed an aorta exiting the right ventricle and a pulmonary artery exiting the left ventricle in parallel. The diagnosis of TGA was confirmed antenatally. HDlive Flow with STIC should be an adjunctive technology to conventional fetal echocardiography for the prenatal diagnosis of TGA.
Artificial intelligence (AI) technology is currently in its third era. Current AI technology is driven by machine learning (ML), particularly deep learning (DL). Deep learning is a computer technology that allows a computational model with multiple processing layers to learn the features of data. Convolutional neural networks have led to breakthroughs in the processing of images, videos, and audio. In medical imaging, computer-aided diagnosis algorithms for diabetic retinopathy, diabetic macular edema, tuberculosis, skin lesions, and colonoscopy classifiers are highly accurate and comparable to clinician performance. Although the application of AI technology in the field of ultrasound (US) has lagged behind other modalities such as radiography, computed tomography (CT), and magnetic resonance imaging (MRI), it has been rapidly applied in the field of obstetrics and gynecology in recent years. The results of AI processing of US images to determine the malignancy of ovarian tumors are comparable to the International Ovarian Tumor Analysis results, and it is now possible to identify each part of the body and calculate the estimated weight from fetal US movies. However, the application of AI to the central nervous system and especially to the fetal heart, which is the main part of fetal US morphological examination, is just beginning to progress.
Fetal facial expressions are useful parameters for assessing brain function and development in the latter half of pregnancy. Previous investigations have studied subjective assessment of fetal facial expressions using four-dimensional ultrasound. Artificial intelligence (AI) can enable the objective assessment of fetal facial expressions. Artificial intelligence recognition of fetal facial expressions may open the door to the new scientific field, such as “AI science of fetal brain”, and fetal neurobehavioral science using AI is at the dawn of a new era. Our knowledge of fetal neurobehavior and neurodevelopment will be advanced through AI recognition of fetal facial expressions. Artificial intelligence may be an important modality in current and future research on fetal facial expressions and may assist in the evaluation of fetal brain function.
Among various congenital central nervous system (CNS) malformations, only cranial bifidum, spinal bifidum, and holoprosencephaly can be diagnosed during the early embryonic/fetal stage. Other CNS dysmorphic diseases occur after 13 weeks of gestation because CNS is formed through several developmental stages, including cell proliferation, neuronal migration, and post-migrational phases, after three gestational months. The recent significant advance of three-dimensional (3D) sonographic technology has accelerated fetal neuroimaging. Since the introduction of transvaginal, transfontanelle neuroimaging technique introduced in clinical practice, combined with 3D technology, has enabled us to conduct systematic neuroimaging analyses. Recently, congenital brain abnormalities have been classified not only by their morphological features but causal genetic factors. In this article, the author describes prenatal neuroimaging diagnoses and genetic causes, and fetal CNS disorders.
Many fetal behaviors are thought to indicate neurological development and may be useful for predicting neurodevelopmental outcomes after birth. In the present article, we review recent fetal behavioral studies focused on early spontaneous movements, eye movements (EMs), regular mouthing movements (RMMs), expression, and our own evaluation method of fetal brain dysfunction. Early spontaneous movement is one of the earliest expressions of neural activity. Changes in fetal EMs are thought to reflect the development of fetal sleep, while RMMs may reflect the development of non-rapid EM sleep. Fetal facial expressions, which may reflect higher brain function, can now be observed in more detail using four-dimensional ultrasound. Furthermore, we propose that assessing fetal brain function by combining multiple behavioral indicators may predict long-term neurodevelopmental outcomes after birth.
Recent technological innovations in ultrasound diagnostic equipment have made it possible for us to obtain ultrasound images of detailed parts such as small organs in fetuses. It may thus be confusing when we come upon small fetal parts that were previously unrecognizable with conventional ultrasound equipment. Therefore, we need to cultivate an understanding of small fetal parts and the fetal-specific anatomy that accompanies fetal development while using high-resolution ultrasound equipment. This review article introduces ultrasound images of small fetal organs visualized with high-resolution ultrasound.
The intraventricular pressure difference (IVPD) is the diastolic suction from the base to the apex during early diastole. This diastolic suction has been shown to actively contribute to rapid filling, which requires adequate filling under low pressure. The IVPD is an important cardiac diastolic functional marker in adults, children, and fetuses. Originally, IVPD could be measured only by direct hemodynamic monitoring; however, velocity estimation was made in the acquired color M-mode imaging, which was analyzed using originally developed programming. In this paper, IVPD analysis in normal fetuses as well as in cases of congenital heart disease has been shown. The IVPD is a useful tool for evaluating fetal diastolic function.
Although various methods have been reported to evaluate fetal cardiac function using ultrasound, two-dimensional speckle-tracking echocardiography (2D-STE), which automatically tracks speckles on B-mode images has the advantage of being angle-independent. Several ultrasound devices are now capable of evaluating fetal cardiac function using 2D-STE, like global longitudinal strain (GLS), wall strain, and fractional area change (FAC). There is also a method called auto fractional shortening (FS) that can automatically calculate the fractional shortening (FS). The most important thing for 2D-STE measurement is to make the B-mode image clear. So, it is important to display the heart as large as possible and to use the highest frame rate possible. There have been many reports of normal and pathological fetuses. However, there are some problems, such as the reference value varies depending on the device or algorithm, and the measurement can only with high-end ultrasound devices, so further development is expected.
Recent advances in fetal echocardiography are HDlive Flow (silhouette) and FetalHQ. HDlive Flow (silhouette) provides novel visual experiences for operators due to the spatial visualization of fetal cardiac structures and allows examiners to easily understand the spatial relationships among fetal cardiac chambers, great arteries, and veins. HDlive Flow (silhouette) may become an important diagnostic tool for the assessment of the normal fetal heart and congenital heart anomaly. FetalHQ consists of a 24-segment sphericity index (SI) and fractional shortening (FS). Fetal 24-segment SI can measure cardiac remodeling and the diastolic shape, whereas 24-segment FS can evaluate the fetal cardiac function and ventricular contractility. Fetal 24-segment SI and FS using FetalHQ may become useful diagnostic modalities in clinical practice. In this review article, we present the latest state-of-the-art HDlive Flow (silhouette) and FetalHQ of normal and abnormal fetal hearts. We also discuss the present and future applicability of these novel techniques to assess normal and abnormal fetal hearts. HDlive Flow (silhouette) and FetalHQ may become important modalities in future research on the fetal heart.
Fetal arrhythmia is frequently found in daily clinical practice. Extrasystole is the most common type of fetal arrhythmia, which is mostly benign and transient. Meanwhile, bradyarrhythmia and tachyarrhythmia are problematic as they cause fetal heart failure. Fetal tachyarrhythmias include supraventricular tachycardia (SVT), atrial flutter (AFL), and ventricular tachycardia (VT). Supraventricular tachycardia are the most commonly reported type of fetal tachyarrhythmia whose mechanisms are classified into AV re-entrant tachycardia (AVRT), AV nodal re-entrant tachycardia (AVNRT), and intra-atrial re-entrant tachycardia (IART). Fetal therapy is performed in cases where extending the gestation period is required. For the fetal therapy of SVT, the classification by VA intervals is used. In 2019, a Japanese prospective study has proposed a protocol of fetal therapy for supraventricular tachyarrhythmia. The efficacy of fetal therapy was 90% (n = 44/49) overall. In fetal bradyarrhythmias, a ventricular rate of <55 bpm is defined as a risk for hydrops fetalis. A prospective study of hydroxychloroquine is currently being conducted in Japan as its prophylactic efficacy was found. An accurate diagnosis is needed to provide appropriate treatment. The recent advancement of ultrasound equipment has enabled higher-resolution imaging than conventional equipment with high temporal and spatial resolutions. In our research, a template matching technique is employed to track tissue architecture in which the speckle pattern is moved to the most similar orientation. With this technique, we estimated the timings of the P and R waves. The reproducibility of such detection for fetuses is currently insufficient. There is still room to be improved.
Superb microvascular imaging (with Doppler Luminance) and SlowflowHD can detect low-velocity blood flow in fetal peripheral small vessels by significantly reducing motion artifacts. Fetal intracranial, intrathoracic, intra-abdominal, and small arm and leg vessels can be clearly identified using these techniques. Moreover, microvasculature of the lung, liver, spleen, adrenal gland, and kidney can also be noted. Superb microvascular imaging (with Doppler Luminance) and SlowflowHD may become a future modality to provide novel information on the antenatal diagnosis of fetal normal and abnormal peripheral vascularities, and the physiologic progress and pathologic etiology of fetal intrathoracic and intra-abdominal organs in clinical practice and future research.
Imperforate anus (IA) is a relatively common gastrointestinal anomaly, usually requiring prompt assessment and treatment after birth. Moreover, >50% of IA cases are associated with other congenital or chromosomal abnormalities. Therefore, the prenatal diagnosis of IA is considered ideal for optimizing neonatal treatment. Imperforate anus had rarely been diagnosed prenatally because of the absence of effective screening and diagnostic methods. Although the prenatal diagnosis of IA remains uncommon, cases of IA diagnosed prenatally have been increasing due to recent advances in the ultrasonographic evaluation of the anorectal anatomical structure of fetuses. A specific sonographic sign, absent or abnormal appearance of the anal sphincter muscles and anal canal mucosa in the tangential view of the fetal perineum, allows for the prenatal diagnosis of IA. High- and intermediate-type IAs are increasingly detected prenatally by this sign, while the prenatal diagnosis of low-type IA remains challenging. Several new sonographic techniques showing the precise anorectal anatomy, such as the sagittal view of the fetal pelvis, transvaginal approach, high-frequency linear transducer, and three-dimensional ultrasound, seem promising to further improve the diagnostic accuracy.
Similar to ultrasound fetal morphological assessment during pregnancy, the placenta and umbilical cord should also be screened around the 20th week of gestation. Additionally, in pathologic conditions such as fetal growth restriction (FGR), preeclampsia, and various placental abnormalities, detail morphological and/or functional evaluations using Doppler methods are required. Superb microvascular imaging (SMI) is a new blood flow imaging technique that employs a unique algorithm to minimize motion artifacts by eliminating signals based on the analysis of tissue movement. While observing a placenta using SMI, dendritic blood flow from the umbilical cord indicating fetal blood flow can be seen on the background of scatter flow indicating maternal intervillous blood flow that beats in line with the mother\'s heartbeat. Using this modality, placental pathological findings can be obtained antenatally, especially histological findings of infarction and avascular villi. In the present review, SMI findings in the various pathologic placenta are demonstrated. These investigations may improve clinical practice in cases with placental abnormalities such as preeclampsia and FGR.
Superb microvascular imaging (SMI) is a new ultrasound Doppler technique that enables the assessment of fine and low-velocity blood flow profiles. This article reviews the sonographic anatomy of the normal placental microvasculature using SMI and the clinical applications for evaluating pathological conditions during pregnancy. The basal plate shows a single layer of blood flow with decidual flows and flows extending into the placenta, on which arterial Doppler waveforms can be detected, indicating jet flows from the spiral arteries into the intervillous space. Several studies have demonstrated the potential for diagnosing the placenta accreta spectrum based on direct SMI findings, including missing decidual tissues and direct invasion of the placenta into the myometrium in the lesion. In a normal pregnancy, the placental villous flows show tree forms by SMI, which is considered blood flow embedded in the stem villi. Because the stem villi provide mechanical stability for the villous trees and control autoregulation of the fetoplacental blood flow in the peripheral villi, the abnormal vasculature characteristics observed by SMI reflect morphological changes in the placenta and dysfunction of the peripheral villous vessels, such as fetal/maternal malperfusion of the placenta.
Vasa previa (VP) is a catastrophic condition which, if unrecognized before the rupture of membranes or labor onset, leads to fetal exsanguination due to the laceration of fetal vulnerable blood vessels lacking the protection of Wharton\'s jelly. Recently, obstetricians seem to be more careful in the scanning of umbilical cord insertion because of the increased awareness of VP and the accumulated knowledge of its risk factors, such as velamentous cord insertion, the presence of second-trimester placenta previa, bilobed placenta, and pregnancy by assisted reproductive technology (ART). However, the detection and management of VP is still challenging. In this review, the authors focus on the ultrasound diagnosis and clinical management of VP.
Preeclampsia (PE) remains one of the leading causes of perinatal morbidity and mortality. Several guidelines recommend assessing the risk of PE based on maternal risk factors. A combination of maternal risk factors such as maternal demographic characteristics, medical history, and biomarkers such as maternal arterial blood pressure, uterine artery Doppler pulsatility index, and maternal serum biochemical markers (placental growth factor and pregnancy-associated plasma protein-A) is considered the best predictor for preterm PE, but not for term PE. The combined screening was superior to screening for maternal risk factors only in terms of predictive ability for preterm PE. According to the ASpirin for evidence-based PREeclampsia prevention (ASPRE) trial, when low-dose (150 mg/day) aspirin was administered to high-risk women from 11 to 14 weeks to 36 weeks of gestation, preterm PE reduced by 62%. Low-dose aspirin started before 16 weeks of gestation (>100 mg/day) reduced the risk of preterm PE. To prevent PE occurrence, it is crucial to assess the risk of PE in early pregnancy.
Superb microvascular imaging (SMI) can detect low-velocity blood flow in the placenta by significantly reducing motion artifacts. Moreover, SMI using an 18-MHz probe generates a high-resolution image of the placental microvasculature in normal and abnormal placentas. In the normal placenta, the increased density of the placental microvasculature with advancing gestation was evident using SMI with an 18-MHz probe. The placental baseline between the placenta and myometrium was also clearly identified. In the first-trimester placenta with an extremely large subchorionic hematoma, decreased vascularity in the placenta adjacent to the hematoma was clearly recognized. In the circumvallate placenta, the placental microvasculature using 18-MHz-SMI was more precisely noted compared with conventional SMI. In a case of pregnancy after a previous uterine fundal incision, a high-resolution SMI with an 18-MHz probe could clearly identify the very thin uterine wall. In cases of placenta accreta spectrum (PAS) during pregnancy and in the retained placenta after birth, various types of PAS were noted, and unique microvasculature was also demonstrated using SMI with an 18-MHz probe. Superb microvascular imaging with an 18-MHz probe may become a future modality to provide novel information on the antenatal evaluation of normal and abnormal placentas, and the physiologic progress of normal placental microvascular development, and precise pathologic findings of placental abnormality in clinical practice and future research.