Ratio of fetal choroid plexus to head size: simple sonographic marker of open spina bifida at 11-13 weeks' gestation.

OBJECTIVES: To measure the ratio of choroid plexus (CP) size to head size in normal fetuses and to compare it to that in fetuses with open spina bifida (OSB) and quantify the subjective sign of a 'dry brain'. METHODS: This was a retrospective study of ultrasound images, obtained during first-trimester screening between 11 and 13 weeks of gestation, from 34 fetuses with OSB and 160 normal fetuses. From the hospital databases, we retrieved images of the fetal head in the transventricular axial plane. We measured the areas of both CPs and the head and calculated the ratio between them. We also measured the longest diameter of each CP and calculated their mean (CP length), and measured the occipitofrontal diameter (OFD) and calculated the ratio of CP length to OFD. Measurements from the OSB fetuses were plotted on crown-rump length (CRL) reference ranges constructed using data from the normal fetuses, and Z-scores were calculated. RESULTS: In the normal fetuses, the CP area increased, while the ratios of CP area to head area and CP length to OFD decreased, with increasing CRL. In 30 of the 34 (88%) fetuses with OSB, both ratios were increased significantly and the CPs filled the entirety of the head, giving the impression of a dry brain. In these cases, the borders of the lateral ventricles could not be identified. CONCLUSIONS: At 11-13 weeks, the majority of fetuses with OSB have reduced fluid in the lateral ventricles such that the CPs fill the head. The dry brain sign is easily visualized during routine first-trimester ultrasound examination while measuring the biparietal diameter, and can be quantified by comparing the size of the CPs to the head size. Until prospective data confirm the usefulness of this sign in screening for OSB, it should be considered as a hint to prompt the examiner to assess thoroughly the posterior fossa and spine. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Cavum septi pellucidi (CSP) ratio: a marker for partial agenesis of the fetal corpus callosum.

OBJECTIVE: While complete agenesis of the corpus callosum is often suspected on fetal ultrasound due to absence of the cavum septi pellucidi (CSP), suspicion of partial agenesis of the corpus callosum (pACC) is a challenge since the CSP is almost always present. The aim of this study was to measure the length and width of the CSP and calculate the length-to-width ratio (CSP ratio), and compare these between fetuses with pACC and normal fetuses. METHODS: In this retrospective case-control study, the length and width of the CSP were measured in the axial plane of the fetal head, and the CSP length-to-width ratio calculated, in 323 normal fetuses and in 20 fetuses with pACC between 20 and 34 weeks' gestation. From the normal population we constructed reference ranges in relation to biparietal diameter (BPD). For all fetuses we calculated Z-scores for the CSP ratio. RESULTS: In the normal population, the length and width of the CSP increased with increasing BPD, while the CSP ratio decreased. The CSP was short (< 5th centile) in 85% (17/20) of fetuses with pACC and wide (> 95th centile) in 65% (13/20). The CSP ratio was small (< 5th centile) in 95% (19/20) of pACC fetuses, with 16/20 (80%) having a ratio below an empirical cut-off of 1.5. Analysis of Z-scores showed that fetuses with pACC had a significantly smaller CSP ratio (P < 0.0001) compared with the normal population. CONCLUSIONS: Fetuses with a normal-sized corpus callosum have a rectangular-shaped CSP, with a CSP ratio > 1.5 in the second half of gestation. Most fetuses with pACC have an abnormally shaped, wide and short CSP, with a decreased CSP ratio. This simple ratio has the potential to identify fetuses at high risk for pACC. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Quality Requirements for the early Fetal Ultrasound Assessment at 11-13+6 Weeks of Gestation (DEGUM Levels II and III).

The early fetal ultrasound assessment at 11 - 13(+6) weeks of gestation remains the cornerstone of care despite the progress in diagnosing fetal chromosomal defects using cell-free fetal DNA (cffDNA) from the maternal circulation. The measurement of nuchal translucency (NT) allows the risk calculation for the fetal trisomies 21, 18 and 13 but also gives information on those fetal chromosomal defects which are at present unable to be detected using cffDNA. Nuchal translucency is the only auditable parameter at 11 - 13(+6) weeks and gives thus information on the quality of the first trimester anomaly scan. In addition it gives indirect information on the risks for fetal defects and for cardiac anomalies. Also the chances for a healthy live baby can be estimated. As experience with first trimester anomaly scanning increases, and the resolution of the ultrasound equipment has increased substantially, more and more details of the fetal anatomy become accessible at the first trimester scan. Therefore fetal anatomical defects and complex anomalies have become amenable to examination in the first trimester. This guideline describes compulsory and optional parameters for investigation at the first trimester scan and outlines a structured method of examining a first trimester fetus at 11 - 13(+6) weeks of gestation.

Ultrasound of the Fetal Veins Part 3: The Fetal Intracerebral Venous System.

The study of the intracerebral venous system in the fetus can only be achieved by means of high-resolution ultrasound equipment with sensitive color Doppler. In the past two decades, there has been a growing interest in the ultrasound examination of the fetal brain with few studies reporting on the brain vasculature during various stages of gestation. In comparison to other fetal venous systems, reports on the assessment of the fetal cerebral venous system are still scarce. This article presents a review on the fetal intracranial venous system with detailed discussions on the anatomy of the superficial and deep cerebral veins. Color Doppler of the main fetal cerebral veins to include the superior sagittal sinus, the straight sinus, the vein of Galen, the internal cerebral veins, the transverse sinuses and others is also discussed. Furthermore, this article highlights abnormal clinical conditions such as aneurysm of the vein of Galen, thrombosis of the dural sinus and variation in the course of some veins such as the straight sinus and falcine sinus. The role of pulsed Doppler examination in normal and growth-restricted fetuses is also discussed.

Maxillary gap at 11-13 weeks' gestation: marker of cleft lip and palate.

OBJECTIVE: To describe a new sign of cleft lip and palate (CLP), the maxillary gap, which is visible in the mid-sagittal plane of the fetal face used routinely for measurement of nuchal translucency thickness. METHODS: This was a retrospective study of stored images of the mid-sagittal view of the fetal face at 11-13 weeks' gestation in 86 cases of CLP and 86 normal controls. The images were examined to determine if a maxillary gap was present, in which case its size was measured. RESULTS: In 37 (43.0%) cases of CLP the defect was isolated and in 49 (57.0%) there were additional fetal defects. In the isolated CLP group, the diagnosis of facial cleft was made in the first trimester in nine (24.3%) cases and in the second trimester in 28 (75.7%). In the group with additional defects, the diagnosis of facial cleft was made in the first trimester in 46 (93.9%) cases and in the second trimester in three (6.1%). A maxillary gap was observed in 96% of cases of CLP with additional defects, in 65% of those with isolated CLP and in 7% of normal fetuses. There was a large gap (>1.5 mm) or complete absence of signals from the maxilla in the midline in 69% of cases of CLP with additional defects, in 35% of those with isolated CLP and in none of the normal controls. CONCLUSIONS: The maxillary gap is a new simple marker of possible CLP, which could increase the detection rate of CLP, especially in isolated cases.

Ultrasound of the fetal veins part 2: Veins at the cardiac level.

In recent years the advent of high-resolution and color Doppler ultrasound has enabled a more comprehensive examination of the veins at the cardiac level. These veins include both the superior and inferior vena cava, the pulmonary veins, the azygos vein, the coronary sinus, and the brachiocephalic (or innominate) vein. This article gives a review of the normal and abnormal conditions of the cardiac venous system. Normal anatomy and abnormal findings of these veins are demonstrated by grayscale and color Doppler. Three groups of anomalies are presented: 1) the interrupted inferior vena cava with azygos continuity, 2) the left persisting superior vena cava and 3) the total and partial anomalous pulmonary venous connections. Many of these abnormal findings can be detected by a dedicated examination of the veins during fetal echocardiography, but some anomalies are detectable by focusing on indirect signs such as the compensatory dilation of other veins.

Ultrasound of the fetal veins part 1: the intrahepatic venous system.

Advances in high-resolution ultrasound combined with color Doppler and three-dimensional (3 D) rendering have contributed to an increasing understanding of the fetal venous circulation in recent years. Still the sonographic evaluation of the venous system in the fetus remains difficult. This article reviews the normal and abnormal intrahepatic venous system. Normal anatomy and abnormal findings of the umbilical vein (UV), the ductus venosus (DV), portal veins, hepatic veins and the inferior vena cava are demonstrated by grayscale, color Doppler and 3D ultrasound and explained by numerous schemes. Typical variants and abnormalities such as agenesis of the DV and portal venous system, persistence of the right UV, UV varix are explained and the clinical value of normal and abnormal Doppler findings in the DV is discussed. Many of these abnormal findings can be detected by a targeted examination of the intrahepatic vasculature with means of color Doppler.

Small biparietal diameter in fetuses with spina bifida on 11-13-week and mid-gestation ultrasound.

OBJECTIVES: To assess whether, at 11-13-week and mid-trimester ultrasound examinations, the biparietal diameter (BPD) in fetuses with open spina bifida is smaller than the reference range. METHODS: In a multicenter retrospective analysis of data from 23 fetuses with open spina bifida diagnosed at 16-24 weeks, BPD at diagnosis was compared with that measured at 11-13 weeks, before diagnosis. Z-scores were calculated for comparison of BPD deviations from the reference range within the groups at 11-13 weeks and 16-24 weeks, and between these two time intervals. RESULTS: BPD Z-scores at 11-13 weeks and 16-24 weeks were significantly lower (P < 0.0001) in fetuses with open spina bifida when compared to the reference range, with mean values of - 1.29 and - 2.14, respectively, corresponding to the 10(th) and 1.5(th) centiles, respectively. At 11-13 weeks only six of the 23 (26%) fetuses with open spina bifida had BPD below the 5(th) centile, in comparison to 16 (69%) at mid-gestation. This was confirmed by paired t-test comparing the first-trimester with the second-trimester BPD measurements, which showed significantly slower growth of the BPD in fetuses with spina bifida. CONCLUSION: In fetuses with open spina bifida, BPD is smaller not only in the second trimester, as previously reported, but also in the first trimester. This is most likely due to loss of cerebrospinal fluid. We suggest that a BPD value < 10(th) centile in an otherwise normally grown fetus at 11-13 weeks' gestation should be considered as a potential subtle early marker for open spina bifida.

[Fetal neurosonography using 3-dimensional multiplanar sonography]. / Fetale Neurosonografie mittels 3-dimensionaler multiplanarer Sonografie.

This review focuses on the examination of the fetal brain, using three-dimensional (3D) ultrasound and the multiplanar rendering mode (MPR). The routine examination of the brain is achieved with axial planes but a dedicated fetal neurosonogram requires additional coronal and sagittal views, in order to provide a complete view of the different brain structures. Because these planes are difficult to obtain under many conditions, the present paper shows how 3D MPR allows one to obtain 1 or multiple reconstructed images from a digital volume. The display can be either as orthogonal planes, tomographic planes with parallel slices or as one single plane of the region of interest, which can be selected by the examiner. This approach allows easily the demonstration of the corpus callosum, the cerebellar vermis, the three-horn view, the foetal hippocampus and other regions. In addition, early neurosonography of the developing brain from the 7th week of pregnancy onwards can be achieved.

Thymic-thoracic ratio in fetuses with trisomy 21, 18 or 13.

OBJECTIVES: To assess thymic size expressed as the thymic-thoracic ratio (TT-ratio) in fetuses with trisomy 21, 18 or 13. METHODS: The TT-ratio, the quotient of the anteroposterior thymic and the intrathoracic mediastinal diameter, was measured in 65 trisomic fetuses between 15 and 36 weeks' gestation, including 30 cases with trisomy 21, 19 with trisomy 18 and 16 with trisomy 13. In addition these 65 fetuses were divided into two groups, according to whether they showed growth that was appropriate-for-gestational age (AGA) (n = 39) or intrauterine growth restriction (IUGR) (n = 26). Measurements were compared with reference ranges from 302 normal fetuses. RESULTS: The TT-ratio was low in 27.7% (n = 18) of the 65 fetuses with aneuploidy. In comparison to normal fetuses (mean TT-ratio, 0.44), those with trisomy 18 or 21 had a significantly smaller TT-ratio (mean, 0.38 (P < 0.001) and 0.40 (P < 0.05), respectively), while those with trisomy 13 did not (mean, 0.43). These values were not as low as those observed previously in fetuses with del.22q11, suggesting a mechanism involving accelerated thymic involution rather than primary thymic hypoplasia. Furthermore, the TT-ratio was significantly lower than normal in both AGA (P < 0.05) and IUGR (P < 0.001) fetuses. CONCLUSION: Fetuses with trisomy 18 or 21, but not trisomy 13, have a small thymus, suggesting accelerated thymic involution in utero. IUGR may contribute to the reduced thymic size in trisomy 18 fetuses. Trisomy 21 fetuses seem to have additional factors leading to a small thymus which could be a possible confirmation of the reduced immune response observed in fetuses and neonates with Down syndrome.

Prospective detection of open spina bifida at 11-13 weeks by assessing intracranial translucency and posterior brain.

We describe a case series of six fetuses with open spina bifida (OSB) from four different prenatal units, where the anomaly was detected at the routine 11-13-week ultrasound examination. Crown-rump length ranged from 49 to 78 mm. All cases were first suspected during nuchal translucency thickness measurement in the mid-sagittal plane of the face. OSB was lumbosacral in five fetuses and cervical in one. The intracranial translucency (IT) was obliterated in two cases, but some fluid was found in the other four cases. However, in all cases the typical landmarks of a normal posterior brain and normal IT were absent. In all six cases the ratio of brainstem diameter to brainstem-occipital bone distance was increased (≥ 1). This detection of an abnormal posterior brain led to a targeted examination and detection of the spinal lesion during the same examination in five cases, whereas in one suspicious case the patient was recalled at 17 weeks, when the abnormality was detected. Two fetuses had both multiple anomalies and trisomy 18. These prospective cases demonstrate the feasibility of using the standard mid-sagittal plane commonly used for NT measurement to assess the IT and the posterior brain and to determine the presence of OSB during NT screening.

The thymic-thoracic ratio in fetal heart defects: a simple way to identify fetuses at high risk for microdeletion 22q11.

OBJECTIVES: To establish reference ranges for the fetal thymic-thoracic ratio (TT-ratio) and to compare results with those from fetuses with congenital heart defects (CHD) with and without microdeletion 22q11 (del.22q11), a condition known to be associated with a hypoplastic thymus. METHODS: TT-ratio was defined as the quotient of the anteroposterior thymic to the intrathoracic mediastinal diameters measured in the three vessels and trachea view. This ratio was measured in a prospective cross-sectional study of 302 normal healthy fetuses between 15 and 39 weeks' gestation. The study group comprised two groups: one group (CHDn) consisted of 90 fetuses with CHD and a normal karyotype with no del.22q11 and the other group (CHD(22)) included 20 fetuses with CHD and a normal karyotype but with proven del.22q11. RESULTS: The TT-ratio of the normal fetuses did not show any statistically significant change during gestation, with a mean value of 0.44. The values of all 90 fetuses of the CHDn group were within the normal range and no different from normal fetuses. However, 19 of the 20 (95%) fetuses in the CHD(22) group had a significantly smaller TT-ratio (P < 0.001) compared with both the CHDn group and the normal fetuses, having a mean value of 0.25. CONCLUSIONS: The TT-ratio is reliable and easy to obtain during fetal echocardiography. Fetuses with CHD and a low TT-ratio can be considered at high risk of having microdeletion del.22q11.