CASE SERIES Case 1A 30-year-old woman was referred at 13 + 1 weeks' gestation for first-trimester screening. The fetus had a crown-rump length (CRL) of 72 mm and a nuchal Figure 1 The mid-sagittal view is the best plane for evaluating intracranial translucency (IT) and the posterior brain region. This ultrasound image in a 13-week fetus illustrates the landmarks typical of a normal examination. The thalamus (Th) and brainstem (BS) have a hypoechoic appearance. The fourth ventricle, also called the IT, appears as an anechoic region with two horizontal echogenic borders, allowing reliable identification: the anterior border of the IT is the posterior border of the BS, and the posterior border of the IT is the choroid plexus (Chor. plex.) of the fourth ventricle. The choroid plexus is a well-recognized structure floating in the fluid of the IT and the future cisterna magna (f.CM), which are still connected to one another. The brainstem-occipital bone distance (BSOB) appears larger than does the brainstem diameter itself. OB, occipital bone. translucency thickness (NT) of 1.7 mm. Routine examination of the posterior brain failed to show the expected normal anatomy (Figure 1) 1,2 ; instead the brainstem appeared thickened and shifted backward toward the occipital bone (Figure 2), such that the ratio of brainstem diameter to brainstem-occipital bone distance (BS/BSOB ratio) was increased 3 , with a value of 1

K E Y W O R D S:congenital heart defects; deletion 22q11; fetal echocardiography; prenatal diagnosis; thymus ABSTRACTObjectives 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

Objectives To assess thymic size expressed as the thymic-thoracic ratio (TT-ratio)

CONTRIBUTIONWhat are the novel findings of this work? Increased fetal choroid-plexus-to-head-size ratio is a new sign for the easy detection of spina bifida in the first trimester. What are the clinical implications of this work?This sign should facilitate detection of spina bifida during the routine first-trimester scan. ABSTRACTObjectives 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. ResultsIn 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, Correspondence to: Prof. R. Chaouigiving 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.

Objective: To derive indices describing the shape of the placenta, relationship of cord insertion to its centre and cord coiling in 200 term, singleton pregnancy placentas from an unselected population. Method: 200 consecutive unselected women were recruited with singleton pregnancy at 37-42 Weeks. Digital analysis of the placenta was performed using ''Image J'' (http://rsb.info.nih.gov/ij) software. Measurements were taken of the X and Y placental axes and, those intersecting the cord insertion. From these measurements we derived: Eccentricity index-(range 0-1) describes the shape of the placenta, calculated by a formula in use in astronomical calculations (http://www.cleavebooks.co.uk/scol/callipse.htm). 0 = circular placenta; an elongated placenta has a value close to 1. Cord centrality index (CCI) (range 0-1) describes the distance of umbilical cord insertion from the centre of placenta and is derived by the dividing the distance of cord insertion from the centre by half the longest diameter of the placenta. The closer to 1 the value of CCI; the closer the cord insertion is to the chorionic plate margin. Results: The median placental eccentricity is 0.47 (IQR 0.36-0.57) and median value of CCI is 0.32 (IQR 0.18-0.48). The indices were compared to z-score of birth weight within the range 37-42 weeks and no significant correlation was found. Conclusion: Contrary to received wisdom, the term placenta (chorionic plate) is not typically round, nor is the cord insertion normally at the centre of the placenta. There is no relationship in the term placenta between birth weight z-score and placental eccentricity or cord centrality indices.