First-trimester sonographic diagnosis of holoprosencephaly: value of the "butterfly" sign

Basic sonographic examination of the fetal brain at 11-13 weeks' gestation: Rationale for a simple and reliable four-step technique

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.

Presentation of ventriculomegaly at 11-14 weeks of gestation: An analysis of longitudinal data

OBJECTIVES

The aim of this study was to examine the value of the sonographic measurements of the choroid plexus and the lateral ventricles at 11-14 gestational weeks in fetuses that had the diagnosis of second-trimester ventriculomegaly (VM) as a clinical reference.

METHODS

The standard axial plane used for biparietal diameter measurement from 2D stored images in the first trimester was used to calculate the ratio between the choroid plexus and lateral ventricle diameter (PDVDR), the choroid plexus and lateral ventricle length (PLVLR) and the choroid plexus and lateral ventricle area (PAVAR) in 100 normal and 15 fetuses diagnosed with second-trimester VM.

RESULTS

In fetuses with VM, the measurements of PDVDR, PLVLR and PAVAR were all significantly smaller compared to normal fetuses (p = < 0.001, <0.001, <0.01). Four out of seven cases with mild VM had measurements below the 5th percentile (57%). 75% of cases with moderate or severe VM had at least one measurement below the 5th percentile.

CONCLUSIONS

Since the axial plane of the fetal head is obtained in all first-trimester routine screenings, the measurements of PDVDR, PLVLR and PAVAR could easily be integrated into routine examinations for an early detection of VM.

Fetal Brain Development: Regulating Processes and Related Malformations

This paper describes the contemporary state of knowledge regarding processes that regulate normal development of the embryonic–fetal central nervous system (CNS). The processes are described according to the developmental timetable: dorsal induction, ventral induction, neurogenesis, neuronal migration, post-migration neuronal development, and cortical organization. We review the current literature on CNS malformations associated with these regulating processes. We specifically address neural tube defects, holoprosencephaly, malformations of cortical development (including microcephaly, megalencephaly, lissencephaly, cobblestone malformations, gray matter heterotopia, and polymicrogyria), disorders of the corpus callosum, and posterior fossa malformations. Fetal ventriculomegaly, which frequently accompanies these disorders, is also reviewed. Each malformation is described with reference to the etiology, genetic causes, prenatal sonographic imaging, associated anomalies, differential diagnosis, complimentary diagnostic studies, clinical interventions, neurodevelopmental outcome, and life quality.

Prenatal diagnosis of a fetus with mosaic ring chromosome 13: Case report and review of the literature

OBJECTIVE

To diagnose the ring chromosome 13 (r(13)) in a fetus, and analyze the genotype-phenotype correlation.

CASE REPORT

A 26-year-old woman who was second pregnancy, underwent amniocentesis at 18 weeks of gestation because of the increased nuchal translucency (NT). Prenatal ultrasound showed the NT thickness was 3.5 mm at 12⁺¹ weeks of gestation and nuchal fold (NF) was 6.1 mm at 18 weeks of gestation, and amniotic fluid karyotype analysis revealed mosaic r(13). CMA detected a 16.293 Mb duplication at 13q21.32q31.1 and 31.303 Mb deletion at 13q31.1q34.

CONCLUSION

R(13) is a very rare chromosomal abnormality. Cytogenetic examination combined with CMA can provide accurate diagnosis and effective information for genetic counseling.

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for r(13), monosomy 13 and idic r(13) by amniocentesis

OBJECTIVE

We present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for ring chromosome 13 [r(13)], monosomy 13 and isodicentric ring chromosome 13 [idic r(13)] by amniocentesis.

CASE REPORT

A 24-year-old woman underwent amniocentesis at 23 weeks of gestation because of intrauterine growth restriction (IUGR) in the fetus. Amniocentesis revealed a karyotype of 46,XY,r(13)[23]/45,XY,-13[10]/46,XY,idic r(13)[2]. The parental karyotypes were normal. Array comparative genomic hybridization (aCGH) on cultured amniocytes revealed the result of arr 13q11q31.3 (19,436,286-92,284,309) × 1.85, arr 13q31.3q34 (92,288,514-115,107,733) × 1 [GRCh37 (hg19)], indicating a 22.82-Mb 13q31.3-q34 deletion and a 15-20% mosaicism for 13q11-q31.3 deletion. The pregnancy was subsequently terminated, and a malformed fetus was delivered with facial dysmorphism. The placental tissues had a karyotype of 46,XY,r(13)[18]/46,XY,-13,+mar[14]/45,XY,-13[8]. Polymorphic DNA marker analysis confirmed a maternal origin of the 13q deletion.

CONCLUSION

Fetus with mosaic r(13), monosomy 13 and idic r(13) may present IUGR on prenatal ultrasound, and fetoplacental cytogenetic discrepancy may exist under such a circumstance.

Prenatal ultrasound findings of holoprosencephaly spectrum: Unusual associations

OBJECTIVE

The objective of this study is to evaluate the prenatal diagnosis, postnatal characteristics, and the spectrum of associated findings in fetuses with holoprosencephaly (HPE).

METHODS

Fetal neurosonograms, postnatal assessment, and chromosomal analysis were performed in a cohort of 25 fetuses with HPE.

RESULTS

The prevalence of HPE in high-risk pregnancies was 4.4:10 000. The alobar subtype was the most frequently encountered, with 17 cases (68%). Interestingly, among them, four cases (16%) presented with the rare agnathia-otocephaly complex. Chromosomal abnormalities were detected in 11 cases (44%), the most frequent being trisomy 13 in seven cases (five alobar, one semilobar, and one lobar HPE), followed by trisomy 18 in two cases with semilobar HPE. One case of alobar HPE had 45, XX, t(18;22) (q10;q10), -18p karyotyping, and one case of semilobar HPE was associated with triploidy. Facial malformations in HPE spectrum ranged from cyclopia, proboscis, and arrhinia that were associated with the alobar subtype to hypotelorism and median cleft that were frequent among the semilobar and lobar subtypes. Associated neural tube defects were identified in 12% of cases.

CONCLUSION

Our study illustrates the clinical and genetic heterogeneity of HPE and describes different chromosomal abnormalities associated with HPE.

First-Trimester Diagnosis of Agnathia-Otocephaly Complex: A Series of 4 Cases and Review of the Literature

First-trimester ultrasound findings in 4 fetuses with agnathia-otocephaly complex are described. In addition, information from 3 cases reported in the literature was also reviewed, for a total of 7 cases analyzed. All 7 fetuses presented with agnathia and 6 with ventrocaudal displacement of the ears (melotia/synotia). Four fetuses had holoprosencephaly. In 6 cases, the parents opted for termination of pregnancy. The remaining case resulted in premature delivery at 26 weeks due to severe polyhydramnios and early neonatal death. This report highlights the important role of ultrasound in the identification of agnathia-otocephaly complex in the first trimester of pregnancy.

Relationship Between Cavum Septi Pellucidi Measurements and Fetal Hypoplastic Left Heart Syndrome or Dextro-Transposition of the Great Arteries

OBJECTIVES

The aim of this study was to compare the size and position of the cavum septi pellucidi (CSP) in fetuses with hypoplastic left heart syndrome (HLHS) or dextro-transposition of the great arteries (d-TGA) with healthy fetuses.

METHODS

The CSP length, CSP width, and frontal lobe length were measured in 185 healthy fetuses (404 scans), 11 fetuses with HLHS (16 scans), and 11 fetuses with d-TGA (12 scans) between January 2005 and April 2016. Each measurement was compared between healthy fetuses and those with HLHS or d-TGA, controlling for the biparietal diameter.

RESULTS

Positive correlations were noted between biparietal diameter and CSP length, CSP width, and frontal lobe length (adjusted R²  = 0.811, 0.821, and 0.878, respectively). An increased CSP length was found in both fetuses with HLHS and those with d-TGA (P < .0001). The CSP width was only increased in fetuses with d-TGA (P = .0466). No difference in the frontal lobe length was noted.

CONCLUSIONS

In fetuses with HLHS, the CSP is increased in length. In fetuses with d-TGA, the CSP is increased in both length and width.

Prenatal diagnosis of holoprosencephaly

Holoprosencephaly is a spectrum of congenital defects of forebrain development characterized by incomplete separation of the cerebral hemispheres. In vivo diagnosis can be established with prenatal brain imaging and disease severity correlates with extent of abnormally developed brain tissue. Advances in magnetic resonance imaging (MRI) over the past 25 years and their application to the fetus have enabled diagnosis of holoprosencephaly in utero. Here, we report on the prenatal diagnosis of holoprosencephaly using MRI as part of a diagnostic and management evaluation at a tertiary and quaternary referral center. Using an advanced MRI protocol and a 1.5-Tesla magnet, we show radiographic data diagnostic for the holoprosencephaly spectrum, including alobar, semilobar, lobar, middle interhemispheric, and septopreoptic variant. Accurate prenatal evaluation is important because the severity of imaging findings correlates with postnatal morbidity and mortality in holoprosencephaly. Therefore, this work has implications for the evaluation, diagnosis, management, and genetic counseling that families can receive during a pregnancy.

Sonographic Development of the Pericallosal Vascularization in the First and Early Second Trimester of Pregnancy

BACKGROUND AND PURPOSE

Anomalies of the corpus callosum are rare. Routine scanning in midtrimester of the pregnancy often fails to identify defective development. The purpose of the study was to identify the pericallosal artery and all its main branching arteries during early gestation from the first trimester onward, to measure the length of the pericallosal artery during its development, and to establish a normal vascular map for each week of development.

MATERIALS AND METHODS

We performed a single-center prospective, longitudinal clinical study in 15 patients between 11 and 22 weeks of gestation. The origin and course of the different blood vessels were identified.

RESULTS

There was a linear association among gestational age, the biparietal diameter, and the length of the pericallosal artery. The curvature of the developing pericallosal artery increases linearly with the gestational age and biparietal diameter, and 4 variations of branching of the callosomarginal artery were observed.

CONCLUSIONS

The pericallosal artery and its branches can be identified and measured from 11 weeks on, and the pericallosal artery takes its characteristic course. A defective course or an abnormal biometry of the pericallosal artery could be an early sonographic marker of abnormal development of the corpus callosum.

Impact of holoprosencephaly, exomphalos, megacystis and increased nuchal translucency on first-trimester screening for chromosomal abnormalities

OBJECTIVES

To examine the prevalence of alobar holoprosencephaly, exomphalos, megacystis and nuchal translucency thickness (NT) ≥ 3.5 mm, the incidence and types of chromosomal abnormalities associated with these conditions and their overall impact on the rate of invasive testing and performance of screening at 11-14 weeks.

METHODS

This was a prospective screening study for trisomies 21, 18 and 13 by the first-trimester combined test at three maternity units in England.

RESULTS

In the study population of 108 982 singleton pregnancies, 870 (0.8%) had abnormal karyotype, including 654 (75.2%) with trisomies 21, 18 or 13 and 216 (24.8%) with other chromosomal abnormalities. The prevalence of alobar holoprosencephaly, exomphalos, megacystis and NT ≥ 3.5 mm was 1 in 2945, 1 in 419, 1 in 1345 and 1 in 119, respectively. Chromosomal abnormalities were observed in 78.4% of cases of holoprosencephaly, 40.8% of exomphalos, 18.5% of megacystis and 48.5% of those with NT ≥ 3.5 mm. The most common chromosomal abnormality associated with holoprosencephaly was trisomy 13, with exomphalos and megacystis was trisomy 18 and with increased NT was trisomy 21. Fetal karyotyping of cases with major fetal defects or increased NT would potentially detect 57% of all chromosomal abnormalities at an invasive testing rate of 1.1%.

CONCLUSION

Major fetal defects and increased NT at 11-13 weeks' gestation are associated with a high risk of chromosomal abnormalities and merit invasive fetal testing. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Alobar Holoprosencephaly With Cebocephaly

Holoprosencephaly (HPE) is a complex brain malformation caused by incomplete fusion of cleavage of the cerebral hemispheres and deep brain structures affecting 6 to 12:10,000 live-born infants. There are three categories of HPE ranging in severity, with alobar holoprosencephaly being the most severe, followed by semilobar holoprosencephaly, and lobar holoprosencephaly being the mildest form. Facial anomalies as well as chromosome anomalies are often associated with HPE. This case study describes a transabdominal sonographic diagnosis of alobar HPE with cebocephaly originally found at 27 weeks 3 days on a patient with no prenatal care.

Holoprosencephaly: antenatal and postnatal diagnosis and outcome

OBJECTIVES

The objectives of this study are to ascertain the clinical outcome and overall survival of holoprosencephaly (HPE) patients diagnosed antenatally and postnatally, to determine the accuracy of antenatal diagnosis and to determine the role of neurosurgical intervention in HPE.

DESIGN

This is a retrospective review over a 10-year period.

PATIENTS

Sixty-three patients were included in the study, 45 were diagnosed by antenatal radiological imaging and 18 were diagnosed by postnatal radiological imaging. Patient data was drawn from Temple Street Children's University Hospital (the national paediatric neurosurgery centre), the National Maternity Hospital in Holle's Street, Dublin, and Our Lady of Sick Children Hospital, Dublin.

METHODS

The study was carried out through a review of antenatal and postnatal radiological imaging and reports, clinical charts, GP letters from patient follow-up and telephone conversations with parents of HPE patients.

RESULTS

Four patients in the antenatal diagnosis group had follow-up foetal MRI confirming HPE. Twelve in this group had radiological follow-up postnatally, and in five of these, HPE was confirmed. The remaining seven were identified as false positive. Alobar HPE constituted 55 % (21/38) of patients with 95 % mortality. Fifty-one percent had a normal karyotype. The overall survival in the antenatal diagnosis group was 13 %. In the postnatal group, 18 patients were identified, 67 % (12/18) lobar and 33 % (6/18) semilobar. Normal karyotype was found in 72 % (13/18), with an overall survival rate of 56 % (10/18). Neurosurgical intervention in both groups mainly consisted of CSF diversion in the form of ventriculoperitoneal (VP) or cystoperitoneal shunt (CP) (13/67).

CONCLUSION

Foetal MRI should be routinely performed in suspected cases of HPE, and reliance on ultrasound alone in the antenatal period may not be sufficient. In our study, there is a high early mortality noted in severe cases of HPE, while milder forms of HPE in children tend to survive beyond infancy albeit with associated complications that required neurosurgical intervention and medical management for other associated systemic anomalies.

Sonographic detection of central nervous system defects in the first trimester of pregnancy

The fetal central nervous system can already be examined in the first trimester of pregnancy. Acrania, alobar holoprosencephaly, cephaloceles, and spina bifida can confidently be diagnosed at that stage and should actively be looked for in every fetus undergoing first-trimester ultrasound. For some other conditions, such as vermian anomalies and agenesis of the corpus callosum, markers have been identified, but the diagnosis can only be confirmed in the second trimester of gestation. For these conditions, data on sensitivity and more importantly specificity and false positives are lacking, and one should therefore be aware not to falsely reassure or scare expecting parents based on first-trimester findings. This review summarizes the current knowledge of first-trimester neurosonography in the normal and abnormal fetus and gives an overview of which diseases can be diagnosed.

Approach to the sonographic evaluation of fetal ventriculomegaly at 11 to 14 weeks gestation

BACKGROUND

The aim of the study was to report the prevalence and associated findings of fetal ventriculomegaly between 11 + 0 and 13 + 6 gestational weeks and to evaluate a sonographic approach to classify first trimester ventriculomegaly in the standard axial plane used for biparietal diameter (BPD) measurement.

METHODS

The ratio between choroid plexus and lateral ventricle diameter (PDVDR), between the choroid plexus and lateral ventricle length (PLVLR) and between the choroid plexus and lateral ventricle area (PAVAR) were calculated from stored 2D images of the axial head plane in 100 normal fetuses and 17 fetuses with ventriculomegaly.

RESULTS

The PDVDR, the PLVLR and the PAVAR were below the 5(th) percentile in 82.4%, 94.1% and 94.1% of the cases with ventriculomegaly. Ventriculomegaly was isolated in 29.4% and associated with further anomalies in 70.6% at the initial evaluation. The mean PLVLR in euploid compared to aneuploid fetuses was significantly lower (0.40 versus 0.53 (p = 0.0332)).

CONCLUSIONS

The measurements of PDVDR, PLVLR and PAVAR are helpful to objectify ventriculomegaly at 11-14 gestational weeks. The PLVLR and PAVAR were superior to PDVDR, since there seems to be rather shrinkage of the choroid plexus than an increased width of the lateral ventricles in the first trimester.

First trimester ultrasound assessment for fetal aneuploidy

Screening tests for trisomy 21 have gradually become more refined and now involve complex statistical models that combine demographic, biophysical, and biochemical parameters to produce individualized risk estimates for pregnant women. An understanding of the evolution of the principles, methods, and statistical techniques applied to Down syndrome screening is valuable as these processes can be transferred to other, more prevalent, adverse pregnancy outcomes. First trimester ultrasound forms the foundation of this process.

Biparietal diameter-to-crown-rump length disproportion in first-trimester fetuses with holoprosencephaly

OBJECTIVES

To determine whether the biparietal diameter measurement is altered in first-trimester fetuses with holoprosencephaly.

METHODS

Cases of holoprosencephaly were collected retrospectively from 4 fetal medicine centers, and first-trimester biparietal diameter measurements were reviewed. The diagnosis of holoprosencephaly was established sonographically by the detection of abnormal choroid plexus morphologic characteristics (absent "butterfly" sign) and the identification of a monoventricular cerebral cavity on axial views of the fetal brain. The proportion of fetuses with biparietal diameter measurements below the 5th percentile for crown-rump length was determined.

RESULTS

Among 45 cases of holoprosencephaly reviewed, 43 had information on both biparietal diameter and crown-rump length measurements. The biparietal diameter was below the 5th percentile for crown-rump length in 14 (32.6%) fetuses. Chromosomal analysis was available in 41; no statistically significant difference in biparietal diameter measurement between those with associated chromosomal anomalies and those without anomalies was noted. A supplementary analysis using head circumference measurement showed an even greater proportion of fetuses with holoprosencephaly with measurements below the 5th percentile for crown-rump length (18 of 42 [42.9%]).

CONCLUSIONS

One-third of first-trimester fetuses with a sonographic diagnosis of holoprosencephaly had a biparietal diameter that was smaller than expected for crown-rump length. In this subset of fetuses, the evaluation of intracranial anatomy for signs of holoprosencephaly may be more difficult to perform due to the smaller size of the brain. Therefore, the detection of a biparietal diameter below the 5th percentile as expected from crown-rump length on the first-trimester scan may be a warning sign of holoprosencephaly and should prompt a detailed examination of the intracranial anatomy.

First trimester screening for holoprosencephaly with choroid plexus morphology ('butterfly' sign) and biparietal diameter

OBJECTIVE

The aim of this study was to determine whether choroid plexus morphology ('butterfly' sign) and biparietal diameter (BPD) are effective sonographic screening tools for holoprosencephaly (HPE) in the first trimester.

METHODS

An axial view of the fetal head was obtained routinely to determine the presence of the 'butterfly' sign in pregnancies presenting for sonographic screening at 11-13 weeks of gestation. The same view was also used to obtain BPD measurements. The definitive diagnosis of HPE was established by the sonographic demonstration of an anterior cerebral monoventricular cavity and thalamic fusion.

RESULTS

During a 9-year study period, 11 068 live fetuses were screened. There were 11 cases of HPE (prevalence 1/1006); all of them were detected by demonstration of an absent 'butterfly' sign with no false-positive cases. The BPD was less than the 5th percentile in 40% of the cases.

CONCLUSIONS

The 'butterfly' sign appears to be a highly sensitive marker for HPE in the first trimester. On the other hand, BPD measurements had a lower sensitivity, implying that microcephaly is not a prominent first-trimester feature in these cases. Incorporation of the 'butterfly' sign into the first trimester anatomy scan is simple and can facilitate the identification of the vast majority of fetuses with HPE in the first trimester.

Reference values for the right and left fetal choroid plexus at 11 to 13 weeks: an early sign of "developmental" laterality?

OBJECTIVES

The purpose of this study was to establish reference values for the length, area, and circumference of the right and left fetal choroid plexus at 11 to 13 weeks with respect to the fetal biparietal diameter and to compare the right to the left side.

METHODS

We conducted a prospective study on 114 fetuses at 11 to 13 weeks undergoing first-trimester screening for aneuploidy and structural fetal abnormalities. After the establishment of the fetal situs, the plane of the "butterfly" was obtained on all fetuses, from which the length, area, and circumference of both the right and left choroid plexus were obtained and the right and left sides compared. Using a paired t test, analysis of variance, scatterplots, and linear and logarithmic fittings, reference ranges and charts for the length, area, and circumference of the choroid plexus were then formulated according to their relationship to the fetal biparietal diameter. P < .05 was considered statistically significant.

RESULTS

Reference values for the length, area, and circumference of the fetal choroid plexus, with respect to the fetal biparietal diameter, were established. There was a statistically significant difference between the right and left sides for all parameters, with all measurements statistically greater on the left side (P < .0001).

CONCLUSIONS

Reference values for the length, area, and circumference of the fetal choroid plexus at 11 to 13 weeks are presented. These may prove to be of clinical importance in the early screening for central nervous system abnormalities. In addition, the statistically significant difference between the right and left sides may be an early sign of "developmental" laterality.

Prenatal Detection of Fetal Anomalies at the 11- to 13-Week Scan—Part I: Brain, Face and Neck

In the last 20 years, the role of first-trimester ultrasound screening has expanded from individual calculation of the risk of aneuploidy through measurement of the nuchal translucency to a powerful technique to evaluate important aspects of the fetal anatomy. Traditionally, the full anatomy scan for detection of structural anomalies has been performed in the second trimester of pregnancy. However, with the implementation of the first-trimester scan at 11 to 13 weeks of gestation many of the structural anomalies traditionally detected in the second trimester can now be identified earlier in pregnancy. In the first part of this review we discuss the main ultrasound findings that may facilitate the prenatal detection of fetal brain, face and neck abnormalities in the first trimester of pregnancy.

How to cite this article

Sepulveda W, Illescas T, Adiego B, Martinez-Ten P. Prenatal Detection of Fetal Anomalies at the 11- to 13-Week Scan—Part I: Brain, Face and Neck. Donald School J Ultrasound Obstet Gynecol 2013;7(4):359-368.

Neurosonoembryology by three-dimensional ultrasound

High-resolution three-dimensional (3D) ultrasound has enabled the visualization of small embryos and fetuses, and embryology in vivo - '3D sonoembryology' - has been established based on conventional embryology. Recently developed imaging techniques allow the definition of in-vivo anatomy including visualization of the embryonic circulation and dynamic features that could not be characterized in fixed specimens. Three-dimensional ultrasound has facilitated increasingly accurate and objective prenatal diagnoses of cranium bifidum/spina bifida, holoprosencephaly and associated anomalies in the first trimester and may allow detection of pathologic central nervous system (CNS) development at an earlier gestational age. It may be no exaggeration to suggest that prenatal diagnoses of fetal abnormalities have shifted from second to first trimester. However, fetal brain develops rapidly in the second trimester, therefore early scanning covers only selected CNS anomalies described in this article and serial continuous observation in the second trimester will be required.

Holoprosencephaly at prenatal diagnosis: analysis of 28 cases regarding etiopathogenic diagnoses

OBJECTIVE

To assess the likelihood of finding an etiopathogenic cause in an ultrasonographic prenatal diagnosis of holoprosencephaly.

MATERIALS AND METHODS

From January 1996 to June 2010, 13 883 prenatal diagnoses through chorionic villus sampling or amniocentesis were made. Every fetus with holoprosencephaly at ultrasound was evaluated. Gestational age, additional ultrasound findings, and fetal karyotype were recorded. Molecular diagnosis and parental karyotype were studied, if relevant.

RESULTS

Twenty-eight fetuses were diagnosed with holoprosencephaly (0.20%). All cases had additional ultrasound findings (100%). A definitive etiology was found in 23 cases (82.14%): karyotype was abnormal in 19 (67.9%) and normal in 8 (28.5%) cases. In the normal karyotype group, although molecular testing was performed in a few cases, one mutation of gene SIX 3 was diagnosed, one diagnosis of dysgnathia complex was made, and two fetuses presented Smith-Lemli-Opitz syndrome. No etiopathogenic diagnosis was made in five fetuses.

CONCLUSIONS

Our results showed that a definitive etiology can be established in most cases of prenatal holoprosencephaly. Chromosomal anomalies were the most frequent finding. However, in euploid fetuses, molecular diagnosis is worthwhile, as different genes with different inheritance patterns may be responsible for this malformation. Thorough evaluation proved beneficial for assessing more accurate prognosis and recurrence risks.

The 11-13-week scan: diagnosis and outcome of holoprosencephaly, exomphalos and megacystis

OBJECTIVE

To determine the prevalence and outcome of fetuses with holoprosencephaly, exomphalos and megacystis diagnosed at 11-13 weeks of gestation.

METHODS

As part of a prospective screening study for trisomy 21 in singleton pregnancies at 11 + 0 to 13 + 6 weeks' gestation, transabdominal ultrasound examination was performed to diagnose holoprosencephaly, exomphalos and megacystis. Fetal karyotype and pregnancy outcome in fetuses with these defects were examined.

RESULTS

Screening was carried out in 57 119 pregnancies. The prevalence of holoprosencephaly, exomphalos and megacystis was 1 : 1298, 1 : 381 and 1 : 1632, respectively. Chromosomal abnormalities, mainly trisomies 18 and 13, were found in 65.9% of fetuses with holoprosencephaly, in 55.3% with exomphalos and in 31.4% with megacystis. There was spontaneous resolution of the defect by 20 weeks in 92.5% of euploid fetuses with exomphalos containing only bowel and in 90% of the euploid fetuses with megacystis and bladder length of < or = 15 mm.

CONCLUSIONS

A high proportion of fetuses with holoprosencephaly, exomphalos and megacystis diagnosed at 11-13 weeks of gestation are aneuploid, but in the majority of cases exomphalos and megacystis represent temporary abnormalities that resolve spontaneously.

Monosomy 18p presenting with holoprosencephaly and increased nuchal translucency in the first trimester: report of 2 cases

OBJECTIVE

The purpose of this series is to describe the first-trimester sonographic findings leading to the diagnosis of monosomy 18p.

METHODS

The sonographic appearance of 2 cases of monosomy 18p, detected as part of first-trimester sonographic screening for aneuploidy at this institution, was reviewed.

RESULTS

Increased nuchal translucency thickness, alobar holoprosencephaly, and facial defects were detected in both cases. Chromosomal analysis by chorionic villus sampling revealed de novo del(18p) in 1 case and monosomy 18p as the result of an 18q isochromosome in the other.

CONCLUSIONS

Increased nuchal translucency thickness in association with brain and face anomalies on a first-trimester scan allowed the early diagnosis of monosomy 18p. Fetuses with holoprosencephaly can be readily identified in the first trimester by examining a cross section of the fetal head looking for the "butterfly" sign. Prenatal karyotyping provides important information regarding the etiology and risk of recurrence in these cases.

Sonoembryology and early prenatal diagnosis of neural anomalies

In the following review, the early development of the central nervous system (CNS), as described by embryologists and anatomists in modern embryological textbooks, is compared with sonoanatomic descriptions from two-dimensional (2D) and three-dimensional (3D) ultrasound studies, week by week in the first trimester. The anatomic descriptions are limited to details that are of interest for the understanding of ultrasound examinations. Further, the detection of main CNS anomalies including spina bifida during the first trimester are presented and discussed. Empty or enlarged brain cavities, or abnormal contours of the head and spine are important diagnostic markers for the detection of CNS anomalies in the very early pregnancy.

Semilobar holoprosencephaly with associated cyclopia and radial aplasia: first trimester diagnosis by means of integrating 2D-3D ultrasound

INTRODUCTION

Holoprosencephaly (HPE) is commonly associated with facial malformations. We present a case of semilobar HPE associated with distal limb defect which was detected at 12 weeks of gestation.

CASE

The fetus had a crown-rump length of 60 mm (12 weeks-4 days), had nuchal translucency thickness of 1.5 mm. Initial two-dimensional (2D) ultrasound revealed the absence of nasal bone, decreased BPD and abnormal profile. Transvaginal 2D ultrasound was effective in the detection of HPE (partially absence of the interhemispheric fissure, fused thalami, the choroid plexuses were not visualized bilateraly: absent 'butterfly' sign), cylopia, absence of the nose and unilateral radial aplasia. Three dimensional (3D) ultrasound provided a better visualization of the associated anomalies. The necropsy result confirmed the sonographic findings: the diagnosis was semilobar HPE, cyclopia, absence of the nose, and the absence of the radius and the thumb in the left arm.

DISCUSSION

Transvaginal 2D sonographic examination is effective in detection of the cases with HPE at first trimester. Fetal morphological study through 3D ultrasound may facilitate the diagnosis of associated anomalies.

Three-dimensional inversion rendering in the first- and early second-trimester fetal brain: its use in holoprosencephaly

OBJECTIVES

To explore the feasibility and added value of three-dimensional (3D) inversion rendering of the developing embryonic/fetal ventricular system, and to apply this display technique to enhance the sonographic examination of holoprosencephaly.

METHODS

3D volumes of the embryonic/fetal brain were acquired from four normal fetuses at 8-11 postmenstrual weeks, and four fetuses diagnosed with holoprosencephaly between 9 and 14 postmenstrual weeks. The volumes were then analyzed offline to obtain inversion rendered 3D shapes of the ventricular systems.

RESULTS

All inversion rendering displays were successful and provided the opportunity to study normal as well as pathological aspects of the early fetal brain.

CONCLUSIONS

Inversion rendering of early fetal brain ventricles is feasible and should be attempted if additional information about the early normal or pathological fetal brain is needed. It may have scientific value in embryologic or genetic studies.

Congenital diaphragmatic hernia in a first-trimester ultrasound aneuploidy screening program

OBJECTIVES

To review our experience with the prenatal detection of congenital diaphragmatic hernia (CDH) in fetuses presenting for ultrasound screening of chromosomal abnormalities in the first trimester.

METHODS

As part of our first-trimester ultrasound protocol, fetuses with a crown-rump length between 45 and 84 mm underwent a limited anatomical assessment in conjunction with nuchal translucency thickness measurement and nasal bone assessment. Cases of CDH diagnosed prenatally or after delivery in this population were identified.

RESULTS

Among the six cases of CDH detected (prevalence of 1 in 927), the first-trimester ultrasound findings were abnormal in five fetuses (83%), including three with increased nuchal translucency only; one with increased nuchal translucency, an intrathoracic stomach, dextrocardia and a cephalocele; and one with normal nuchal translucency thickness and a small, complex intrathoracic mass later confirmed as the fetal stomach. The diagnosis of CDH was confidently made in the first trimester in one case, in the second trimester in three cases, and after birth in the remaining two cases.

CONCLUSION

The diagnosis of CDH in the first trimester is difficult, especially in those cases in which the defect is small or late migration of the abdominal viscera occurs. Therefore, screening for CDH in the first trimester is unlikely to be effective.

First trimester three-dimensional transvaginal imaging of alobar holoprosencephaly associated with proboscis and hypotelorism (ethmocephaly) in a 46,XX fetus

A 19-year-old woman was scanned at 10(+6) weeks gestation by 2D-3D ultrasound. The fetus had a crown-rump length of 40.9 mm, with the cephalic pole occupied by a single cystic cavity measuring 10.6 x 7.7 x 6.8 mm and severe hypotelorism associated with mid-facial hypoplasia. 3D ultrasound confirmed the malformations seen on the 2D scan and enabled the visualization of a proboscis and a low-set right ear. Fetal karyotyping was performed by chorionic villus sampling. Due to major fetal malformations of the fetus, the patient opted for termination of pregnancy. First trimester sonographic diagnosis of holoprosencephaly relies on bilateral visualization of choroid plexuses in what has been called the 'butterfly' sign. Differential diagnosis between holoprosencephaly and hydranencephaly may be difficult in the first trimester of pregnancy. However, midline structures such as falx cerebri, interhemispheric fissure and third ventricle are present in hydranencephaly and are absent in alobar holoprosencephaly, and thalami are never fused in hydranencephaly. 3D ultrasound has demonstrated an increased definition of anatomical abnormalities of malformations, compared with 2D ultrasound, and has proven to be crucial in the decision-making process of parents and in later prenatal counseling, especially in this case where necroscopy examination was refused by the parents. Images obtained by 3D ultrasound gave detailed insight into this ventral midline anomaly, depicting much of the disordered prosencephalic development.

What information on fetal anatomy can be provided by a single first-trimester transabdominal three-dimensional sweep?

OBJECTIVE

To determine the extent to which the fetal anatomy detailed in The Fetal Medicine Foundation Nuchal Translucency software program can be visualized using the stored dataset of a single transabdominal three-dimensional (3D) volume sweep of the entire fetus between 11 and 13 + 6 weeks' gestation.

METHODS

Transabdominal 3D volume sweeps of the entire fetus in 273 singleton pregnancies were performed in the mid-sagittal plane (Observer 1). The datasets were copied to a compact disc and manipulated on a personal computer using ultrasound software in the sectional planes mode. Each dataset was manipulated and analyzed by two separate investigators (Observers 2 and 3), who were blinded to each other's results.

RESULTS

The crown-rump length (CRL) and nuchal translucency thickness (NT) were measured by both investigators in 100% and 84.6% of cases, respectively. Increasing maternal weight significantly reduced the odds of the investigators being able to visualize most of the anatomical characteristics tested, and increasing CRL significantly increased the odds of the investigators being able to identify half of the characteristics tested. There were negligible clinical differences in measurements of NT and CRL between the three observers. Paired t-tests and intraclass correlations showed that, while there were statistically significant differences for NT measurements, the effect size was small and would have little clinical impact on screening results.

CONCLUSION

A single transabdominal 3D sweep at 11 to 13 + 6 weeks' gestation provides appropriate views of the fetus for evaluation of both anatomy and NT in the vast majority of cases.

Prenatal diagnosis of alobar holoprosencephaly with cystic hygroma

OBJECTIVE

Holoprosencephaly is a kind of brain anomaly characterized by inadequate cleavage of the prosencephalon during early embryogenesis. In addition, holoprosencephaly associated with cystic hygroma and hydrops fetalis has never been reported. In this article, we report a rare case of holoprosencephaly associated with cystic hygroma and hydrops fetalis diagnosed prenatally.

CASE REPORT

A 28-year-old woman, gravida 2, para 0, artificial abortion 1, was referred to our antenatal clinic at 16 weeks of gestation due to fetal cystic hygroma detected by prenatal routine ultrasonography at a local hospital. In our clinic, single ventricle with fused thalami and cystic mass at the fetal neck as well as hydrops fetalis were noted by level II ultrasound. Under the impression of holoprosencephaly with cystic hygroma and hydrops fetalis, termination of pregnancy with misoprostol was undertaken. The histopathology of fetal autopsy confirmed our diagnosis and disclosed additional intracranial abnormalities.

CONCLUSION

Fetus with holoprosencephaly might have other associated structural abnormalities. Cystic hygroma and hydrops fetalis are rare associations. Meticulous sonographic examination to depict the associated defects are necessary in any fetus with holoprosencephaly.

Ultrasound and fetal diagnosis

PURPOSE OF REVIEW

The purpose of this review is to highlight publications from the last year that have advanced the use of ultrasound in obstetrics.

RECENT FINDINGS

Anatomic examination of the fetus in the first trimester has been emphasized because it allows for early diagnosis of many conditions. The prevalence of absent nasal bone, a marker for trisomy 21, in euploid fetuses depends on ethnicity. Nasal bone hypoplasia is another marker for Down syndrome. Studies on genetic screening in the first trimester have involved various serum analytes, adjustments in timing and calculations, use in multiple gestations, and the association of extreme measurements with adverse outcomes. A first-trimester integrated screening approach, which incorporates nuchal translucency, nasal bone, crown-rump length, pregnancy-associated plasma protein-A, and free beta-human chorionic gonadotropin, has the potential to maximize detection rates of Down syndrome and trisomy 18 and minimizes the screen-positive rate. The value of combining first and second-trimester results in sequential, contingent, or integrated screening protocols has been assessed. Isolated mild ventriculomegaly (10-12 mm) may prove to be a normal variant, and the role of 'soft' ultrasound markers in genetic counseling continues to be debated. Anomaly or high-risk status detection in the second trimester has been enhanced by the use of Doppler, 3D/4D ultrasound, and magnetic resonance imaging.

SUMMARY

Imaging techniques have been critical in the development of screening methods for Down syndrome or trisomy 18 and for euploid fetuses at high risk for adverse outcomes.

Early detection of fetal structural abnormalities

Most published data on the detection of fetal anomalies at 11-14 weeks are from specialized centres with considerable experience in fetal anomaly scanning. However, there is still limited information on the feasibility and limitations of the screening of these anomalies compared with the now classical mid-gestation screening. This review indicates that overall, the detection rate of fetal anomalies at 11-14 weeks is 44% compared with 74% by the mid-pregnancy scan. Major abnormalities of the fetal head, abdominal wall and urinary tract, and of the umbilical cord and placenta, can be reliably detected at 10-11 weeks of gestation. Detection of other anomalies such as spina bifida, diaphragmatic hernia or heart defects is limited before 13 weeks of gestation. So far it cannot be stated that routine first trimester screening can be used on a large scale to evaluate the fetal spine and heart in the general population. In particular, in screening for congenital heart defects, the ability to perform a full cardiac examination increases from 20% at 11 weeks to 92% at 13 weeks. The early prenatal diagnosis of these anomalies may be improved by screening at 13-14 weeks rather than during the first trimester.