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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.

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OBJECTIVE: To determine the key sonographic features for the diagnosis of sirenomelia in the first trimester of pregnancy. METHODS: Cases of sirenomelia from several prenatal diagnosis centers were retrospectively identified and reviewed. The diagnosis was established through the detection of fused lower limbs. Additional sonographic findings were also noted. RESULTS: A total of 12 cases were collected. The most striking sonographic finding was the detection of malformed lower limbs, which appeared to be fused and in an atypical position. Nuchal translucency thickness was mildly increased in three cases (25%). An abdominal cyst, representing the dilated blind-ending bowel, was noted in seven cases (58%). Color flow imaging detected a single umbilical artery in six cases (50%) and the associated intra-abdominal vascular anomalies in three cases (25%). No cases of aneuploidy were detected. The pregnancy was terminated in nine cases (75%) and intrauterine demise occurred in the remaining three cases (25%). CONCLUSIONS: The sonographic detection of abnormal lower limbs or an intra-abdominal cyst located laterally during the first-trimester scan may be warning signs of sirenomelia. This should prompt a detailed examination of the fetal lower body and intra-abdominal anatomy, including the main abdominal vessels, in order to look for additional confirmatory findings.

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Los tumores intracraneales fetales son poco comunes, pero cuando aparecen están asociados con una elevada mortalidad. Muchos de los tumores cerebrales congénitos a menudo provocan la muerte fetal intrauterina, lo que limita la evaluación precisa de su prevalencia e incidencia del tumor. El más frecuente es el teratoma, que se caracteriza por estar constituido por células dependientes de las tres capas germinales. Estos tumores suelen detectarse en las ecografías habituales de control prenatal y, frecuentemente, son tan grandes que se dificulta determinar su origen. Por ello, ante la sospecha ecográfica, se recomienda completar el estudio con una RM fetal. Se presenta un caso de una gestante de 20 semanas, en quien se detecta un tumor intracraneal fetal en una ecografía de control prenatal. Se decide completar el estudio con una RM fetal en la que se visualiza una masa dependiente de la glándula pineal con extensión anterior, compatible con teratoma. Se decidió la interrupción voluntaria del embarazo, y en el estudio histológico tras la necropsia se confirmó un teratoma inmaduro. La RM es la prueba de imagen de elección tras la sospecha diagnóstica ecográfica. Por su alta resolución aporta información relevante que permite valorar mejor la arquitectura interna del tumor, así como su origen y extensión. Además, sirve para evaluar el resto de estructuras intracraneales.

Fetal intracranial tumors are rare but, when they do occur they are associated with high fetal mortality. Many of the congenital brain tumors often result in intrauterine fetal death, limiting accurate assessment of tumor prevalence and incidence. The most frequent is teratoma, which is characterized by cells dependent on the three germ layers. These tumors are usually detected in the usual prenatal control ultrasounds, and are often so large that it is difficult to determine their origin. When ultrasound suspicion exists, a fetal MRI study is recommended. The case of a 20- week pregnant woman is presented, in which a fetal intracranial tumor was detected on a prenatal control ultrasound. It was decided to complete the study with a fetal MRI in which a pineal gland mass with anterior extension, compatible with teratoma, was visualized. Voluntary termination of pregnancy was decided, and the histological study after necropsy confirmed that it was an immature teratoma. MRI is the imaging test of choice after suspected diagnostic ultrasound, as its high resolution provides relevant information that allows better assessment of the internal architecture of the tumor, as well as its origin and extension. In addition, it also serves to evaluate the rest of the intracranial structures.

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Se presentan dos casos de resonancia magnética (RM) fetal en los que se detectan anomalías de las eminencias ganglionares (EG): un caso en una gestación única y otro en una gestación gemelar con solo uno de los fetos afectado. Las alteraciones en las eminencias ganglionares son entidades poco frecuentes, con muy pocos casos publicados, tanto por RM como por ecografía fetal, que suelen asociarse con alteraciones neurológicas graves. Se describen los hallazgos por RM de la patología de las EG en estos dos casos, no visibles en la ecografía previa.

We present two cases of fetal MRI where anomalies of the ganglionic eminences (GE) are detected, one case in a single pregnancy and another in a twin gestation with only one of the affected fetuses. Alterations in the ganglionic eminences are rare entities, with very few published cases, both by MRI and fetal ultrasound, which are usually associated with severe neurological alterations. The MR findings of the pathology of the GE in these two cases are described. These findings were not visible on the previous ultrasound.

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Three-dimensional ultrasound and magnetic resonance imaging are powerful imaging techniques that are used increasingly in evaluating fetal anatomy. In this chapter, we review the main applications of these imaging modalities in current practice and present an overview of the malformations that may benefit from assessment with three-dimensional ultrasound and magnetic resonance imaging.

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We describe a new technique that can facilitate the first-trimester examination of the fetal palate using the Volume NT algorithm (Samsung Medison, Seoul, Korea), a program that automatically detects the exact midsagittal plane of the head and is primarily designed for semiautomatic measurement of the nuchal translucency thickness. Three-dimensional (3D) data sets from the fetal face were captured with Volume NT and subsequently reformatted with the Oblique View software to obtain orthogonal views of the primary and secondary palate in coronal and axial planes, respectively. By testing this method in selected 3D data sets obtained retrospectively (n = 12) and prospectively (n = 28), we were able to extract clinically acceptable views of the fetal palate in all cases. This preliminary report shows that with this new 3D automation development, early evaluation of the fetal palate is feasible and reproducible and could be easily incorporated into the first-trimester sonographic protocol once its ability to detect abnormal cases is demonstrated.

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Ultrasonography is used routinely during pregnancy to screen and diagnose fetal anomalies. Two-dimensional ultrasound is usually adequate in women at low risk for malformations. When technical factors limit optimal evaluation or a malformation is suspected, further imaging with three-dimensional ultrasound and magnetic resonance imaging is becoming increasingly common. Three-dimensional ultrasound allows the manipulation of data acquired from two-dimensional ultrasound to recreate an infinite number of views, thereby enhancing the ability to evaluate the fetal anatomy. When three-dimensional ultrasound is either unavailable or inadequate, fetal magnetic resonance imaging permits detailed evaluation of the suspected anomaly and assesses the presence of associated anomalies. In this chapter, we review the techniques, advantages, limitations, and clinical applications of these two fetal imaging modalities.

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Aunque la ecografía (US) es el método de elección en la evaluación del feto, la resonancia magnética (RM) es una técnica complementaria a la US en el diagnóstico de las anomalías fetales. Entre las ventajas de la RM se destacan un excelente contraste tisular, un campo de visión grande y una relativa operador-independencia. La mayoría de los trabajos previos de RM fetal han estudiado el sistema nervioso central (SNC). Sin embargo, la RM es útil en la evaluación de las anomalías torácicas y abdominales. En este artículo se muestran los diferentes aspectos por RM de las anomalías fetales torácicas y abdominales y se discuten las indicaciones y ventajas de la RM fetal.(AU)

Ultrasonography (US) is the method of chotee in fetal examina³on. However, magnetic resonance (MR) imaging is a complementan/ technique that contributes to the aecurate diagnosis of fetal anomalies. The benefits of MR include excellent tissue contrast, large field of view and relative operator independence. Most previous reports on fetal MR have focused on central nervous system (CNS). However, MR is a useful tool for the examination of fetal thoracic and abdominal anomalies. This article illustrates the different features of fetal thoracic and abdominal anomalies on MR, and further discusses the indications and benefits of fetal MR.(AU)

RESUMO

Aunque la ecografía (US) es el método de elección en la evaluación del feto, la resonancia magnética (RM) es una técnica complementaria a la US en el diagnóstico de las anomalías fetales. Entre las ventajas de la RM se destacan un excelente contraste tisular, un campo de visión grande y una relativa operador-independencia. La mayoría de los trabajos previos de RM fetal han estudiado el sistema nervioso central (SNC). Sin embargo, la RM es útil en la evaluación de las anomalías torácicas y abdominales. En este artículo se muestran los diferentes aspectos por RM de las anomalías fetales torácicas y abdominales y se discuten las indicaciones y ventajas de la RM fetal.(AU)

Ultrasonography (US) is the method of chotee in fetal examinaüon. However, magnetic resonance (MR) imaging is a complementan/ technique that contributes to the aecurate diagnosis of fetal anomalies. The benefits of MR include excellent tissue contrast, large field of view and relative operator independence. Most previous reports on fetal MR have focused on central nervous system (CNS). However, MR is a useful tool for the examination of fetal thoracic and abdominal anomalies. This article illustrates the different features of fetal thoracic and abdominal anomalies on MR, and further discusses the indications and benefits of fetal MR.(AU)

RESUMO

Aunque la ecografía (US) es el método de elección en la evaluación del feto, la resonancia magnética (RM) es una técnica complementaria a la US en el diagnóstico de las anomalías fetales. Entre las ventajas de la RM se destacan un excelente contraste tisular, un campo de visión grande y una relativa operador-independencia. La mayoría de los trabajos previos de RM fetal han estudiado el sistema nerviodo central (SNC). Sin embargo, la RM es útil en la evaluación de las anomalías torácicas y abdominales. En este artículo se muestran los diferentes aspectos por RM de las anomalías fetales torácicas y abdominales y se discuten las indicaciones y ventajas de la RM fetal...

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OBJECTIVES: To determine the feasibility of obtaining adequate 3-dimensional (3D) data sets to examine the fetal secondary palate during the second-trimester anatomy scan. METHODS: During a 3-month period, 3D data sets of the fetal secondary palate were obtained from consecutive women undergoing routine second-trimester scans. Only structurally normal singleton fetuses with a normal upper lip on 2-dimensional (2D) sonography were included. Three-dimensional data sets were obtained using a mechanical transducer with a 45° sweep and the same settings as for the standard 2D scan, ideally when the fetus was facing the transducer, with mild extension of the head, and the ultrasound beams projecting caudally to cranially to avoid shadowing from the primary palate or mandible. No additional scanning time was allocated for examination of the palate. Acquired 3D data sets were analyzed offline using dedicated software, and the secondary palate was assessed using the "flipped face" technique. RESULTS: Ninety-seven women met entry criteria and underwent second-trimester scans at a median gestational age of 22 completed weeks (range, 18-23 weeks). In 13 (13.4%) cases, it was not possible to obtain a midsagittal view of the face for capturing 3D volume data sets due to fetal position. Additional factors limiting visualization were shadowing from the primary palate in fetuses with flexion of the head in 30 (30.9%) cases, interposition of, or shadowing from, fetal arms or legs in 11 (11.3%), inability to reproduce a true midsagittal plane in 8 (8.2%), and poor image quality in 1 (1%). Therefore, it was only possible to assess the secondary palate in 34 (35.1%) cases. CONCLUSIONS: It is not feasible to obtain adequate 3D data sets for offline analysis of the fetal secondary palate in almost two-thirds of second-trimester fetuses during the routine scan. However, suboptimal visualization is primarily due to factors related to fetal position rather than equipment or image quality. This finding suggests that a dedicated scan, during which adequate time can be devoted to obtaining a satisfactory position in which the fetal face can be evaluated, may be warranted in high-risk cases.

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La resonancia magnética (RM) fetal es una técnica de imagen en auge, útil en la valoración del cerebro y columna fetal. Ayuda a estudiar el desarrollo cerebral fetal y se puede realizar un diagnóstico precoz de las anomalías congénitas. La imagen de RM muestra gran resolución de contraste y permite diferenciar mejor que la ecografía entre hallazgos normales y patológicos. Además, algunas malformaciones cerebrales o lesiones destructivas ocultas en la ecografía prenatal pueden ser detectadas por RM. Revisamos las indicaciones, utilidad, seguridad, aspectos técnicos de la RM fetal y la apariencia del desarrollo cerebral fetal, y evaluamos su contribución en el diagnóstico de las patologías de las diferentes regiones cerebrales y de la patología espinal fetal.

Fetal MR imaging (MRI) is an increasingly available technique used to evaluate the fetal brain and spine, because it provides a unique opportunity to evaluate fetal brain development and to make an early diagnosis of congenital abnormalities. MRI allows a better differentiation between normal and abnormal signal intensity of fetal tissues due to its higher contrast resolution compared to prenatal sonography (US). Therefore, structural abnormalities such as brain malformations and destructive lesions that could be sonographically occult on prenatal sonography can be detected at fetal MRI. We review indications, utility, safety, and technical aspects of fetal MR imaging and the appearance of normal fetal brain development evaluating its contribution in the diagnosis of fetal diseases of different brain regions and spinal disorders.

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Objetivos: Valorar la precisión de la determinación ecográfíca del sexo fetal entre las 11 y las 14 semanas en una cohorte no seleccionada de gestantes. Métodos: Se realizó un estudio prospectivo transversal en una serie consecutiva de 636 gestaciones entre las 11 y 14 semanas, en gestantes que acudieron para el estudio ecográfco rutinario de primer trimestre. Se examinó la región genital del feto en un plano mediosagi-tal, visualizando el signo sagital y la dirección en la que apunta el tubérculo genital (craneal en los varones, caudal en las mujeres) ambos indicadores del sexo fetal. La confrmación clínica del sexo fetal se obtuvo después del parto por confrmación telefónica, o por el cariotipo en casos con amniocentesis por indicaciones convencionales. Resultados: Se consiguió asignar el sexo fetal correctamente en el 86,3 por ciento de los fetos. La precisión de la asignación ecográfca del sexo fetal fue mayor en varones que en mujeres (el 90,6 por ciento de los varones fueron asignados correctamente vs el 83,1 por ciento de las mujeres, p<0,05), y se incrementó con la edad gestacional desde un 72 por ciento entre las 11 y 11+6 semanas, un 92 por ciento entre las 12 y las 12+6 semanas, hasta un 95 por ciento entre las 13 y las 13+6 semanas. Conclusión: La determinación ecográfíca del sexo fetal tiene una elevada tasa de precisión a partir de las 13 semanas, lo que sugiere que las pruebas invasivas para la exclusión de enfermedades ligadas al X podrían obviarse cuando se identifca un feto varón a esta edad gestacional. Sin embargo, en fetos identifcados como mujeres esta decisión deberá posponerse hasta una edad gestacional más avanzada.

Objective: To assess the accuracy of fetal gender determination by ultrasound at 11-14 weeks of gestation in a large cohort of unselected population. Methods: A prospective cross-sectional study was performed in 636 consecutive pregnancies at 11-14 weeks of gestation, attending for frst trimester ultrasound screening. The genital region was examined in the mid-sagittal plane to detect the sagittal sign and the direction in which the genital tubercle pointed (cranial for males, caudal for females) both as markers of fetal gender. The clinical confrmation of fetal gender was obtained from telephonic interviews after delivery or from karyotype in cases scheduled to amniocentesis for conventional indications. Results: Fetal gender was correctly determined by ultrasound in 86.3 percent of the fetuses. The accuracy of sex assignment was higher in male fetuses than in female fetuses (90.6 percent of the males fetuses vs 83.1 percent of the females were correctly assigned, p<0.05) and increased with gestational age from 72 percent at 11-11+6 week's to 92 percent at 12-12+6 week's, and 95 percent at 13-13+6 week's gestation (p<0.01). Conclusion: Prenatal gender assignment by ultrasound has a high accuracy rate at 13 to 13+6 weeks. These results suggest that invasive testing can probably be performed in fetuses identifed as males at this gestational age. However in fetuses identifed as females, the decision regarding invasive testing should be postponed until a higher gestational age is achieved.

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