Posterior brain in fetuses with trisomy 18, trisomy 13 and triploidy at 11 to 13 weeks' gestation

Accuracy of qualitative and quantitative cranial ultrasonographic markers in first-trimester screening for open spina bifida and other posterior brain defects: a systematic review and meta-analysis

BACKGROUND

The significant number of qualitative and quantitative ultrasound markers described for first-trimester screening of open spina bifida (OSB) and other posterior brain defects (oPBD) has resulted in their complex implementation and interpretation for a widespread screening and in a lack of consensus regarding diagnostic accuracy.

OBJECTIVES

To assess and compare the accuracy of qualitative and quantitative cranial sonographic markers at 11-14 weeks of gestation for the detection of OSB and oPBD.

SEARCH STRATEGY

A systematic literature search was performed in MEDLINE and COCHRANE from 2009 to April 2020.

SELECTION CRITERIA

Studies assessing the diagnostic accuracy of quantitative and/or qualitative ultrasound signs to predict OSB and oPBD were included. Cohort studies and case-control studies were also considered.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed the risk of bias. The overall pooled estimate and a summary receiver operating characteristic curve was estimated for each subgroup (qualitative and quantitative assessment).

MAIN RESULTS

Twenty-three studies were included in our meta-analysis. The pooled sensitivity and specificity for qualitative assessment were 76.5% and 99.6%, and for quantitative assessment were 84.5% and 96.3%, respectively; specificity for the qualitative ultrasound signs was significantly higher (P = 0.001). The overall sensitivity of cranial sonographic markers for the screening of oPBD was 76.7% and specificity was 97.5%.

CONCLUSIONS

The qualitative approach demonstrated greater specificity, so this would appear to be more appropriate for daily screening, as a first-line tool, whereas the quantitative approach should be reserved for expert ultrasound.

TWEETABLE ABSTRACT

This study highlights the relevance of first-trimester qualitative ultrasound signs in the screening of open spina bifida.

Posterior fossa assessment in the axial view of the head at 11-14 weeks of gestation in normal and aneuploid fetuses

Posterior fossa ultrasound appearance may offer clues for brain anomalies as early as the first trimester. The purpose of the study was to find an easy, reproducible method to examine the posterior fossa. From January 2017 to March 2018, 132 consecutive pregnancies presenting for first-trimester screening, were selected at 11-14 weeks' gestation. An oblique axial view of the fetal head was routinely achieved with visualization of the posterior fossa, wherein the cisterna magna (CM) and the fourth ventricle (V4) anteroposterior diameter was measured. Moreover, 81 patients had a follow-up scan at 19-24 weeks, and the CM and transverse cerebellar diameter (TCD) were measured. Normal ranges were established at 11-14 weeks for CM and V4 according to crown-rump length (CRL). The 50th centile for CM ranges from 1.2 mm to 2.3 mm at a CRL between 45 and 85 mm. The V4 50th centile ranges from 1.8 to 2.4 mm. A positive correlation was found between the first-trimester and second-trimester CM diameter and between the first-trimester V4 and second-trimester TCD. There is an inverse correlation between the first-trimester CM and second-trimester TCD. The measurements of different components of the posterior fossa in the first trimester cannot predict the size of CM and TCD in the second trimester. The presence of the three hypoechoic structures (cerebral peduncles, V4, and CM) separated by two hyperechoic lines is easy to see and measure.

First trimester detection of fetal open spina bifida using BS/BSOB ratio

BACKGROUND

Despite the well-known second trimester ultrasound signs, current possibilities of in utero surgical repair of open spina bifida require a timely detection of the spine defect.

OBJECTIVE

To evaluate the diagnostic accuracy of the ratio between brain stem (BS) diameter and its distance to the occipital bone (BSOB) (BS/BSOB ratio) in the detection of fetuses with open spina bifida at first trimester ultrasound.

METHODS

A systematic review and meta-analysis of diagnostic accuracy was performed by searching seven electronic databases from their inception to February 2019 for all studies assessing the association between BS/BSOB ratio and diagnosis of spine bifida. Diagnostic accuracy of BS/BSOB ratio in prenatal diagnosis of spine bifida was assessed as sensitivity, specificity, positive and negative likelihood ratios (LR + and LR-), and area under the curve (AUC) on SROC curves.

RESULTS

Four studies, including 17,598 fetuses with 23 cases of open spina bifida, were included in the meta-analysis. BS/BSOB ratio showed pooled sensitivity of 0.70 (95% CI 0.47-0.87; I² = 78.3%), specificity of 1.00 (95% CI 0.99-1.0; I² = 99.2%), LR + and LR- of 51.44 (95% CI 9.53-277.64; I² = 85.5%) and 0.23 (95% CI 0.04-1.17; I² = 64.8%), respectively, and an AUC of 0.9649.

CONCLUSION

First trimester BS/BSOB ratio has a high diagnostic accuracy in detecting fetuses with open spina bifida.

Is Cisterna Magna Width a Useful First-Trimester Marker of Aneuploidy?

OBJECTIVE

To assess whether the cisterna magna (CM) width measured in first-trimester fetuses is a useful marker for aneuploidy detection.

METHODS

This was a prospective study in 2 different cohorts in a tertiary referral center. The first cohort comprised 913 fetuses from the general pregnancy population during the period 2012-2016 and was used to construct the CM reference ranges applying the λ-μ-σ (LMS) method. The second cohort included 714 high-risk fetuses undergoing chorionic villus sampling during the period 2012-2016. Mean detection rates using the 95th percentile for CM width observed in chromosomal anomaly groups were compared with those obtained in chromosomally normal fetuses.

RESULTS

The 50th percentile for CM ranged from 1.66 to 2.75 mm when crown-rump length (CRL) increased from 45 to 84 mm. Among high-risk fetuses, the following chromosomal anomalies were diagnosed in 125 (17%) fetuses: trisomy 21 (n = 63), trisomy 18 or 13 (n = 21), monosomy X (n = 9), submicroscopic anomalies (n = 11), and other anomalies (n = 22). The mean CM width for euploid fetuses was 2.4 mm (1.13 multiples of the median, MoM). While CM width was significantly increased in trisomy 21 (mean 2.7 mm; 1.23 MoM; p > 0.05), no differences were found in the other anomaly groups. Among the 63 fetuses with trisomy 21, a CM width above the 99th percentile was observed in 23 fetuses (37%).

CONCLUSIONS

The new reference range for CM width at 11-13 weeks of gestation did not differ from previous studies. In first-trimester fetuses with trisomy 21, CM width appears to be increased, although its value as an ultrasound marker is limited, because of its detection rate of 37%.

Diagnosis of Fetal Structural Anomalies at 11 to 14 Weeks

OBJECTIVES

To assess the performance of first-trimester ultrasound (US) in identifying major fetal structural abnormalities in an unselected population.

METHODS

We conducted a retrospective analysis of all pregnancies that underwent the 11- to 14-week scan in the Fetal Medicine Department of Filantropia Hospital in Bucharest, which were prospectively examined within our screening program. The purpose of the first-trimester US was to evaluate the risk for chromosomal abnormalities and to conduct fetal anatomic examination using a detailed protocol.

RESULTS

Our population consisted of 7480 pregnant patients (7576 fetuses). The follow-up was completed for 6045 patients (6114 fetuses). The prevalence of major structural anomalies was 1.89%. In the first trimester, we identified 79% of all major structural anomalies. The highest detection rates were achieved for abdominal wall defects (100%), major central nervous system anomalies (88%), cardiac defects (74%), and skeletal anomalies (71%). The nuchal translucency was increased in 35% of the cases with structural anomalies, and 95% of these were diagnosed in the first trimester. Seventy percent of the patients who presented with structural anomalies and a normal nuchal translucency were diagnosed in the first trimester.

CONCLUSIONS

Our results emphasize the importance of performing a detailed US examination at 11 to 14 weeks' gestation in identification of fetal structural defects.

Non-visualization of choroid plexus of fourth ventricle as first-trimester predictor of posterior fossa anomalies and chromosomal defects

OBJECTIVE

To assess non-visualization of the choroid plexus of the fourth ventricle (CP-4V) as a simple, qualitative and reproducible first-trimester ultrasound feature of the posterior fossa for the prediction of central nervous system (CNS) anomalies and chromosomal defects.

METHODS

First-trimester three-dimensional ultrasound datasets of the fetal brain were obtained prospectively from 65 consecutive normal singletons and retrospectively from 27 fetuses identified as having an abnormal posterior fossa on first-trimester ultrasound examination, and randomly combined to form the final study group. The stored ultrasound volumes were analyzed offline by two accredited sonologists, who were not aware of the final diagnoses. The CP-4V was assessed by multiplanar navigation and classified as visible or non-visible in its normal position depending on whether or not the echogenic structure that separates the fourth ventricle from the cisterna magna was identified in both midsagittal and axial planes. Correlation with subsequent second-trimester ultrasound, fetal magnetic resonance imaging, or postmortem or postnatal findings was performed to determine the predictive value of the first-trimester findings.

RESULTS

Among the 92 ultrasound datasets analyzed, 73 (79%) were acquired transabdominally and 19 (21%) transvaginally. The CP-4V was classified as visible in 64 cases and non-visible in 28 cases, with agreement between the two observers in both sagittal and axial planes in all but one case. Twelve of the 28 (43%) fetuses with non-visible CP-4V were subsequently diagnosed as having a CNS malformation (open spina bifida (n = 6), Dandy-Walker malformation (n = 2), Blake's pouch cyst (n = 2), cephalocele (n = 1) and megacisterna magna (n = 1)). In addition, 20 of these 28 (71%) fetuses had aneuploidy (trisomy 18 (n = 10), triploidy (n = 5), trisomy 13 (n = 3), Turner syndrome (n = 1) or trisomy 21 (n = 1)). There was only one false-positive case, in which the CP-4V was classified as absent in a normal fetus.

CONCLUSIONS

Non-visualization of the CP-4V in the first trimester appears to be a strong marker of posterior fossa anomalies and chromosomal defects. Qualitative evaluation of this anatomic structure is simple, feasible and reproducible, and its routine assessment during the first-trimester scan may facilitate the early detection of CNS anomalies and associated fetal aneuploidy. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Appearance of fetal posterior fossa at 11-14 weeks in fetuses with Dandy-Walker malformation or chromosomal anomalies

OBJECTIVE

To describe the sonographic appearance of fetal posterior fossa anatomy at 11-14 weeks of pregnancy and to assess the outcome of fetuses with increased intracranial translucency (IT) and/or brainstem-to-occipital bone (BSOB) diameter.

METHODS

Reference ranges for brainstem (BS), IT and cisterna magna (CM) measurements, BSOB diameter and the BS : BSOB ratio were obtained from the first-trimester ultrasound examination of 233 fetuses with normal postnatal outcome (control group). The intraobserver and interobserver variability of measurements were investigated using 73 stored ultrasound images. In addition, a study group of 17 fetuses with increased IT and/or BSOB diameter was selected to assess outcome.

RESULTS

No significant intraobserver or interobserver variability was found for any measurement in the control group. In the study group, IT was increased in all cases and BSOB diameter was above the 95(th) centile of the calculated normal range in all but two (88%) cases. In 13/17 study cases, only two of the three posterior brain spaces were recognized on ultrasound. These 13 fetuses had a larger BSOB diameter than did the four cases that showed all three posterior brain spaces, and had severe associated anomalies including Dandy-Walker malformation (DWM) and/or chromosomal anomalies.

CONCLUSIONS

Visualization of the fetal posterior fossa anatomy at 11-14 weeks' gestation is feasible. Increased fluid in the posterior brain at 11-14 weeks, particularly in the case of non-visibility of the septation that divides the future fourth ventricle from the CM, is an important risk factor for cystic posterior fossa malformations, in particular DWM, and/or chromosomal aberrations. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

The BS/BSOB Ratio in Aneuploidy Fetuses at 11-13 Weeks Gestation

Objective: The posterior fossa of normal fetuses was evaluated and compared with those having chromosomal abnormalities at 11-13+6 weeks' gestation in Chinese population. Methods: In 518 normal fetuses referred to first trimester screening, fetal brain stem (BS) and brain stem to occipital bone distance (BSOB) were measured prospectively. The BS and BSOB were also measured on stored images in fetuses with confirmed trisomy 21 (n = 38), Trisomy 18 (n = 26), Trisomy 13 (n = 8), and monosomy X (n = 8). Results: The BS diameter and BSOB distance correlated linearly with fetal crown-rump length (CRL) by regression analysis. The BS to BSOB ratio was below the 5th percentile in 2 (5.26%), 11 (44%), 4 (50%) and 4 (50%) fetuses with trisomy 21, trisomy 18, trisomy 13 and monosomy X, respectively. Thus, both BS and BS/BSOB ratio were significantly lower in trisomy 18, trisomy 13 and monosomy X fetuses when compared to the reference range but not in fetuses with Trisomy 21. Conclusion: In ultrasound scans performed at the 11-13+6 gestation weeks, fetuses with trisomy 18, 13, and monosomy X had lower BS/BSOB ratios. But trisomy 21 fetuses did not show significant differences in posterior fossa compared to the normal population.

Fetal diagnostic indications for second and third trimester outpatient pregnancy termination

OBJECTIVE

To determine the frequency of diagnostic indications among women seeking to terminate pregnancies for reasons of fetal abnormality, spontaneous fetal demise, or a genetic disorder in a private outpatient clinic specializing in late outpatient abortion procedures.

METHOD

A total of 1005 women requested termination of pregnancy for reasons of genetic disorder, fetal anomaly, or fetal demise over 20 years (1992-2012). Gestational ages ranged from 12 to 39 weeks. In all cases, a documented diagnosis of fetal abnormality or fetal demise was made prior to referral. Records were reviewed to verify fetal diagnosis for all patients seeking termination of pregnancy for reasons of fetal disorder. Major complications included major unintended surgery, hemorrhage requiring transfusion, or pelvic infection.

RESULTS

Preoperative diagnoses included the following: chromosomal abnormalities (n = 378), genetic syndromes and single gene disorders (n = 30), structural anomalies (n = 494), and other conditions (n = 103). These include 26 cases of spontaneous fetal demise and nine selective terminations of one abnormal twin. The major complication rate was 0.5%.

CONCLUSIONS

The majority of diagnoses were in the categories of genetic disorder and neurologic abnormality.

DFLAT: functional annotation for human development

Background

Recent increases in genomic studies of the developing human fetus and neonate have led to a need for widespread characterization of the functional roles of genes at different developmental stages. The Gene Ontology (GO), a valuable and widely-used resource for characterizing gene function, offers perhaps the most suitable functional annotation system for this purpose. However, due in part to the difficulty of studying molecular genetic effects in humans, even the current collection of comprehensive GO annotations for human genes and gene products often lacks adequate developmental context for scientists wishing to study gene function in the human fetus.

Description

The Developmental FunctionaL Annotation at Tufts (DFLAT) project aims to improve the quality of analyses of fetal gene expression and regulation by curating human fetal gene functions using both manual and semi-automated GO procedures. Eligible annotations are then contributed to the GO database and included in GO releases of human data. DFLAT has produced a considerable body of functional annotation that we demonstrate provides valuable information about developmental genomics. A collection of gene sets (genes implicated in the same function or biological process), made by combining existing GO annotations with the 13,344 new DFLAT annotations, is available for use in novel analyses. Gene set analyses of expression in several data sets, including amniotic fluid RNA from fetuses with trisomies 21 and 18, umbilical cord blood, and blood from newborns with bronchopulmonary dysplasia, were conducted both with and without the DFLAT annotation.

Conclusions

Functional analysis of expression data using the DFLAT annotation increases the number of implicated gene sets, reflecting the DFLAT’s improved representation of current knowledge. Blinded literature review supports the validity of newly significant findings obtained with the DFLAT annotations. Newly implicated significant gene sets also suggest specific hypotheses for future research. Overall, the DFLAT project contributes new functional annotation and gene sets likely to enhance our ability to interpret genomic studies of human fetal and neonatal development.