Prenatal diagnosis of fetal skeletal dysplasias by combining two-dimensional and three-dimensional ultrasound and intrauterine three-dimensional helical computer tomography

Prenatal ultrasound findings and prenatal diagnosis of fetal skeletal dysplasia

OBJECTIVE

To analyze the value of prenatal ultrasound and molecular testing in diagnosing fetal skeletal dysplasia (SD).

METHODS

Clinical data, prenatal ultrasound data, and molecular results of pregnant women with fetal SD were collected in the ultrasound department of our clinic from May 2019 to December 2021.

RESULTS

A total of 40 pregnant women with fetal SD were included, with 82.5% exhibiting short limb deformity, followed by 25.0% with central nervous system malformations, 17.50% with facial malformations, 15% with cardiac malformations, and 12.5% with urinary system malformations. The genetic testing positive rate was 70.0% (28/40), with 92.8% (26/28) being single-gene disorders due to mutations in FGFR3, COL1A1, COL1A2, EVC2, FLNB, LBR, and TRPV4 genes. The most common SD subtypes were osteogenesis imperfecta (OI), thanatophoric dysplasia (TD), and achondroplasia (ACH). The gestational age (GA) at initial diagnosis for TD, OI, and ACH was 16.6, 20.9, and 28.3 weeks, respectively (p < 0.05), with no significant difference in femoral shortening between the three groups (p > 0.05). Of the OI cases, 5 out of 12 had a family history.

CONCLUSION

Short limb deformity is the most prevalent phenotype of SD. When fetal SD is suspected, detailed ultrasound screening should be conducted, combined with GA at initial diagnosis, family history, and molecular evidence, to facilitate more accurate diagnosis and enhance prenatal counseling and perinatal management.

Prenatal diagnosis to identify compound heterozygous variants in PKDCC that causes rhizomelic limb shortening with dysmorphic features in a fetus from China

BACKGROUND

Rhizomelic limb shortening with dysmorphic features (RLSDF) has already been a disorder of the rare autosomal recessive skeletal dysplasia, just having a few reported cases. RLSDF is caused by protein kinase domain containing, cytoplasmic(PKDCC)gene variants. In this study, we describe the clinical features and potential RLSDF molecular etiology in a fetus from China.

METHODS

Genomic DNA (gDNA) extracted from the fetal muscle tissue and parents' peripheral blood was subjected to chromosomal microarray analysis (CMA) and trio-based whole exome sequencing (Trio-WES). The candidate pathogenic variants were verified by using Sanger sequencing.

RESULTS

Trio-WES identified two compound heterozygous variants in PKDCC, c.346delC (p.Pro117Argfs*113) and c.994G > T (p.Glu332Ter), inherited from the father and mother, respectively. Both variants are classified as pathogenic according to American College of Medical Genetics and Genomics guidelines.

CONCLUSIONS

We reported the first prenatal case of RLSDF caused by PKDCC in the Chinese population. Our findings extended the variation spectrum of PKDCC and emphasized the necessity of WES for the early diagnosis of skeletal dysplasia and other ultrasound structural abnormalities in fetuses.

Exploration of the fetal skeleton by ultra-low-dose computed tomography: guidelines from the Fetal Imaging Task Force of the European Society of Paediatric Radiology

Skeletal anomalies are rare, requiring a systematic ultrasound (US) examination of each skeletal part when there is suspicion of a skeletal dysplasia. Although US examination can provide good evaluation of the fetal bones and cartilage, ultra-low-dose three-dimensional (3-D) multi-detector computed tomography (CT) is a useful complementary tool that can significantly improve prenatal diagnostic accuracy in select cases. Given that ultra-low-dose fetal CT remains an irradiating technique, indications should result from a multidisciplinary consensus, acquisition protocols should be optimized and the reporting standardized. In this paper we discuss guidelines from the Fetal Imaging Task Force of the European Society of Paediatric Radiology for indications, protocols and reporting of ultra-low-dose fetal CT.

Imaging of Congenital Skeletal Disorders

Osteochondrodysplasias are the result of the expression of gene mutations. The phenotypes in osteochondrodysplasias evolve through life, with the possibility that previously unaffected bones may be involved at later stages of growth. Due to the variable time of onset, the diagnosis may be made prenatally, at birth, or later. Certainty in the diagnosis is sometimes only achieved as the patient matures and the disease evolves. Radiographic evaluation is a fundamental part of the diagnostic work-up of congenital skeletal disorders and in most cases the first tool used to arrive at a diagnosis. This review describes the imaging characteristics, specific signs, and evolution of several skeletal dysplasias in which diagnosis may be directly or indirectly suggested by radiologic findings. A definitive accurate diagnosis of a congenital skeletal abnormality is necessary to help provide a prognosis of expected outcomes and to counsel parents and patients.

Prenatal diagnosis of Meier-Gorlin syndrome 7: a case presentation

Background

Meier-Gorlin syndrome 7 (MGS7) is a rare autosomal recessive condition. We reported a fetus diagnosed with Meier-Gorlin syndrome 7. The antenatal sonographic images were presented, and compound heterozygous mutations of CDC45 on chromosome 22 were identified by whole-exome sequencing (WES).

Case presentation

Fetal growth restriction (FGR), craniosynostosis, and brachydactyly of right thumb were found in a fetus of 28th gestational weeks. The fetus was diagnosed as MGS7 clinically. After extensive counseling, the couple opted for prenatal diagnosis by cordocentesis and termination of pregnancy. Karyotype analysis and WES were performed. Chromosomal karyotyping showed that the fetus was 46, XY. There were 2 mutations of CDC45, the causal gene of MGS7 on chromosome 22, which were inherited from the couple respectively were identified by WES. Facial dysmorphism, brachydactyly of right thumb, and genitalia abnormally were proved by postpartum autopsy, and craniosynostosis was confirmed by three-dimensional computed tomography (3D-CT) reconstruction.

Conclusions

It is possible to detect multiple clinical features of Meier-Gorlin syndrome in prenatal sonography. Deteriorative FGR complicated with craniosynostosis indicates MGS7. Combination of 2D and 3D ultrasonography helps to detect craniosynostosis. The affected fetus was confirmed a compound heterozygote of CDC45 related MGS by whole-exome sequencing, which is critical in identifying rare genetic diseases.

Current Overview of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI), or brittle bone disease, is a heterogeneous disorder characterised by bone fragility, multiple fractures, bone deformity, and short stature. OI is a heterogeneous disorder primarily caused by mutations in the genes involved in the production of type 1 collagen. Severe OI is perinatally lethal, while mild OI can sometimes not be recognised until adulthood. Severe or lethal OI can usually be diagnosed using antenatal ultrasound and confirmed by various imaging modalities and genetic testing. The combination of imaging parameters obtained by ultrasound, computed tomography (CT), and magnetic resource imaging (MRI) can not only detect OI accurately but also predict lethality before birth. Moreover, genetic testing, either noninvasive or invasive, can further confirm the diagnosis prenatally. Early and precise diagnoses provide parents with more time to decide on reproductive options. The currently available postnatal treatments for OI are not curative, and individuals with severe OI suffer multiple fractures and bone deformities throughout their lives. In utero mesenchymal stem cell transplantation has been drawing attention as a promising therapy for severe OI, and a clinical trial to assess the safety and efficacy of cell therapy is currently ongoing. In the future, early diagnosis followed by in utero stem cell transplantation should be adopted as a new therapeutic option for severe OI.

Antenatal diagnosis of CHARGE syndrome: Prenatal ultrasound findings and crucial role of fetal dysmorphic signs. About a series of 10 cases and review of literature

Although the prognosis of CHARGE syndrome can be highly variable from mild until severe, final diagnosis is difficult to establish in utero. The aim of our study is to compare antenatal and postnatal findings in a retrospective cohort of 10 successive patients with a positive CHD7 gene variant in order to identify the specific prenatal features for CHARGE syndrome diagnosis. Fetal ultrasound, follow-up and supplementary investigations are collected and compared to postnatal findings. Congenital heart defect (7/10), choanal atresia (7/10) and tracheoesophageal atresia (4/10) are the most frequent fetal anomalies found. Inner and external ear anomalies appear as the keystone (constant features) for prenatal diagnosis of CHARGE syndrome in fetuses with multiple anomalies and normal microarray karyotype. External ear malformations are identified in all cases by 3D ultrasound when carefully evaluated. MRI and temporal bone CT-Scan are second line useful tools to assess the diagnosis when looking for semicircular canal agenesis, arhinencephaly and/or choanal atresia. Before availability of prenatal exome sequencing in clinical routine, present findings lead to the recommendation that fetuses, with congenital heart defect (mainly septal and conotruncal), cleft lip/palate or unexplained polyhydramnios should carefully be screened for clues suggesting CHARGE syndrome using 2D and 3D ultrasound, MRI and temporal bone CT-Scan. When CHARGE syndrome is suspected with normal molecular karyotype, CHD7 gene sequencing must be offered.

The Health & Economic Disparities of Congenital Musculoskeletal Disease Worldwide: An Analysis of 25 Years (1992-2017)

Background: Large disparities exist in congenital musculoskeletal disease burden worldwide. The purpose of this study is to examine and quantify the health and economic disparities of congenital musculoskeletal disease by country income level from 1992 to 2017. Methods: The Global Burden of Disease database was queried for information on disease burden attributed to "congenital musculoskeletal and limb anomalies" from 1992 to 2017. Gross national income per capita was extracted from the World Bank website. Nonparametric Kruskal-Wallis tests were used to compare morbidity and mortality across years and income levels. The number of avertable DALYs was converted to an economic disparity using the human-capital and value of a statistical life approach. Results: From 1992 to 2017, a significant decrease in deaths/100 000 was observed only in upper-middle and high income countries. Northern Africa, the Middle East, and Eastern Europe were disproportionately affected. If the burden of disease in low- and middle- income countries (LMICs) was equivalent to that in high income countries (HICs), 10% of all DALYs and 70% of all deaths attributable to congenital musculoskeletal disease in LMICs could be averted. This equates to an economic disparity of about $2 billion to $3 billion (in 2020 $USD). Conclusion: Considerable inequity exists in the burden of congenital musculoskeletal disease worldwide and there has been no change over the last 25 years in total disease burden and geographical distribution. By reducing the disease burden in LMICs to rates found in HICs, a large proportion of the health and economic consequences could be averted.

Model-Agnostic Method for Thoracic Wall Segmentation in Fetal Ultrasound Videos

The application of segmentation methods to medical imaging has the potential to create novel diagnostic support models. With respect to fetal ultrasound, the thoracic wall is a key structure on the assessment of the chest region for examiners to recognize the relative orientation and size of structures inside the thorax, which are critical components in neonatal prognosis. In this study, to improve the segmentation performance of the thoracic wall in fetal ultrasound videos, we proposed a novel model-agnostic method using deep learning techniques: the Multi-Frame + Cylinder method (MFCY). The Multi-frame method (MF) uses time-series information of ultrasound videos, and the Cylinder method (CY) utilizes the shape of the thoracic wall. To evaluate the achieved improvement, we performed segmentation using five-fold cross-validation on 538 ultrasound frames in the four-chamber view (4CV) of 256 normal cases using U-net and DeepLabv3+. MFCY increased the mean values of the intersection over union (IoU) of thoracic wall segmentation from 0.448 to 0.493 for U-net and from 0.417 to 0.470 for DeepLabv3+. These results demonstrated that MFCY improved the segmentation performance of the thoracic wall in fetal ultrasound videos without altering the network structure. MFCY is expected to facilitate the development of diagnostic support models in fetal ultrasound by providing further accurate segmentation of the thoracic wall.

Prenatal diagnosis of fetal skeletal dysplasia using 3-dimensional computed tomography: a prospective study

Background

Fetal skeletal dysplasia (FSD) comprises a complex group of systemic bone and cartilage disorders. Many FSD phenotypes have indistinct definitions, making definitive prenatal diagnosis difficult. The condition is typically diagnosed using sonography; however, three-dimensional computed tomography (3D-CT) also aids in making a prenatal diagnosis. This study aimed to examine the efficacy of 3D-CT in the prenatal diagnosis of FSD by comparing the diagnostic accuracy of fetal sonography and 3D-CT.

Methods

On suspicion of FSD based on ultrasound examination, we performed 3D-CT prenatally to obtain detailed skeletal information on FSD. To minimize exposure of the fetuses to radiation without compromising image quality, we used predetermined 3D-CT settings for volume acquisition.

Results

Nineteen fetuses were suspected of having skeletal dysplasia based on ultrasonography findings. Of these, 17 were diagnosed with FSD using 3D-CT. All 17 fetuses diagnosed with FSD prenatally were confirmed postnatally to have the condition. The postnatal diagnosis (campomelic dysplasia) differed from the prenatal diagnosis (osteogenesis imperfecta) in only one infant. Sixteen cases (94.1%) were diagnosed both prenatally and postnatally with FSD. Five infants had lethal skeletal dysplasia; one died in utero, and four died as neonates. We determined the appropriate delivery method for each infant based on the prenatal diagnosis.

Conclusions

3D-CT is a valuable tool for augmenting ultrasound examinations in the diagnosis of FSD. While improving the diagnostic tool of sonography is essential in cases of suspected FSD, 3D-CT imaging is indispensable for diagnosis and classification, enabling better planning for resuscitation of the infant after birth.

Trial registration

University Hospital Medical Information Network (UMIN) Center trial registration number is UMIN000034744. Registered 1 October, 2018 – Retrospectively registered.

Demonstration of Human Fetal Bone Morphology with MR Imaging: A Preliminary Study

Purpose:

CT is a useful modality for the evaluation of fetal skeletal dysplasia but radiation exposure is unavoidable. The purpose of this study is to compare the usefulness of MRI and CT for evaluating the fetal skeletal shape.

Methods:

This study was approved by our Institutional Review Board. Fetal specimens (n = 14) were scanned on a 3T MRI scanner using our newly-developed sequence. It is based on T2*-weighted imaging (TR, 12 ms; TE for opposed-phase imaging, 6.1 ms, for in-phase imaging, 7.3 ms; flip angle, 40°). The specimens were also scanned on a 320 detector-row CT scanner. Four radiologists visually graded and compared the visibility of the bone shape of eight regions on MRI- and CT-scans using a 5-point grading system.

Results:

The diagnostic ability of MRI with respect to the 5th metacarpals, femur, fibula, and pelvis was superior to CT (all, P < 0.050); there was no significant difference in the evaluation results of observers with respect to the cervical and lumbar spine, and the 5th metatarsal (0.058 ≤ P ≤ 1.000). However, the diagnostic ability of MRI was significantly inferior to CT for the assessment of the bone shape of the thoracic spine (observers A and C: P = 0.002, observers B and D: P = 0.001).

Conclusion:

The MRI method we developed represents a potential alternative to CT imaging for the evaluation of the fetal bone structure.

Optimal non-invasive diagnosis of fetal achondroplasia combining ultrasonography with circulating cell-free fetal DNA analysis

OBJECTIVES

To assess the performance of non-invasive prenatal testing (NIPT) for achondroplasia using high-resolution melting (HRM) analysis, and to propose an optimal diagnostic strategy combining ultrasound examination and cell-free fetal DNA (cffDNA) analysis.

METHODS

In this prospective multicenter study, cffDNA was extracted from blood of pregnant women at risk for fetal achondroplasia (owing to paternal achondroplasia, previous affected child or suspected rhizomelic shortening) and of pregnant low-risk controls. The presence of either one of the two main fibroblast growth factor receptor 3 gene (FGFR3) mutations was determined using HRM combined with confirmation by SNaPshot minisequencing. Results were compared with phenotypes obtained using three-dimensional computed tomography or postnatal examination, and/or molecular diagnosis by an invasive procedure. Fetal biometry (head circumference and femur length) was analyzed in order to develop a strategy in which cffDNA analysis for diagnosis of achondroplasia is offered only in selected cases.

RESULTS

Eighty-six blood samples from women at risk for fetal achondroplasia and 65 from controls were collected. The overall sensitivity and specificity of NIPT were 1.00 (95% CI, 0.87-1.00) and 1.00 (95% CI, 0.96-1.00), respectively. Critical reduction in femur length of affected fetuses could be observed from 26 weeks' gestation.

CONCLUSIONS

HRM combined with SNaPshot minisequencing is a reliable method for NIPT for achondroplasia. Its implementation in routine clinical care combined with ultrasonography is an efficient strategy for the non-invasive diagnosis of achondroplasia. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

A Newborn with Multiple Fractures in Osteogenesis Imperfecta: A Case Report

Introduction:

Multiple bone fractures in a newborn can be associated with osteogenesis imperfect (OI). OI is a rare genetic disorder that causes Type I collagen synthesis disturbance results in bone fragility.

Case Report:

We present a female newborn which had numerous fractures of the humerus, bilateral clavicle, and bilateral femur. Her delivery was at 36 weeks gestation by spontaneous vaginal delivery. She had has not any pathological symptom at 2 weeks after birth, the patient had a fracture of the humerus, bilateral clavicle, and femur without any trauma. Genetic analysis of the patient was reported and OI diagnosed. The patient was followed up for 8 months with regularly and without any complication.

Conclusion:

Multiple fractures with OI in an infant after birth may require an accurate orthopedic plan for diagnosing and treatment.

Fetal dose conversion factor for fetal computed tomography examinations: A mathematical phantom study

This study aimed to examine the relationship between fetal dose and the dose-length product, and to evaluate the impact of the number of rotations on the fetal doses and maternal effective doses using a 320-row multidetector computed tomography unit in a wide-volume mode. The radiation doses for the pregnant woman and the fetus were estimated using ImPACT CT Patient Dosimetry Calculator software for scan lengths ranging from 176 to 352 mm, using a 320-row unit in a wide-volume mode and an 80-row unit in a helical scanning mode. In the 320-row unit, the fetal doses in all scan lengths ranged from 3.51 to 6.52 mGy; the maternal effective doses in all scan lengths ranged from 1.05 to 2.35 mSv. In the 80-row unit, the fetal doses in all scan lengths ranged from 2.50 to 3.30 mGy; the maternal effective doses in all scan lengths ranged from 0.83 to 1.68 mSv. The estimated conversion factors from the dose-length product (mGy・cm) to fetal doses (mGy) for the 320-row unit in wide-volume mode and the 80-row unit in helical scanning mode were 0.06 and 0.05 (cm-1 ) respectively. While using a 320-row MDCT unit in a wide-volume mode, operators must take into account the number of rotations, the beam width as automatically determined by the scanner, the placement of overlap between volumetric sections, and the ratio of overlapping volumetric sections.

[Lethal osteogenesis imperfecta: antenatal diagnosis]

L'ostéogenèse imparfaite (OI) est un groupe hétérogène de maladies affectant le collagène de type I et caractérisées par une fragilité osseuse. Les formes létales sont rares et se caractérisent par une micromélie avec déformation des membres. Un diagnostic anténatal d'OI létale a été fait dans deux cas, par échographie à 17 et à 25 semaines d'aménorrhée, complélées par un scanner du squelette fœtal dans un cas. Une interruption thérapeutique de grossesse a été indiquée dans les deux cas.

Radiation doses for pregnant women in the late pregnancy undergoing fetal-computed tomography: a comparison of dosimetry and Monte Carlo simulations

The purposes of this study were (1) to compare the radiation doses for 320- and 80-row fetal-computed tomography (CT), estimated using thermoluminescent dosimeters (TLDs) and the ImPACT Calculator (hereinafter referred to as the "CT dosimetry software"), for a woman in her late pregnancy and her fetus and (2) to estimate the overlapped fetal radiation dose from a 320-row CT examination using two different estimation methods of the CT dosimetry software. The direct TLD data in the present study were obtained from a previous study. The exposure parameters used for TLD measurements were entered into the CT dosimetry software, and the appropriate radiation dose for the pregnant woman and her fetus was estimated. When the whole organs (e.g., the colon, small intestine, and ovaries) and the fetus were included in the scan range, the difference in the estimated doses between the TLD measurement and the CT dosimetry software measurement was <1 mGy (<23 %) in both CT units. In addition, when the whole organs were within the scan range, the CT dosimetry software was used for evaluating the fetal radiation dose and organ-specific doses for the woman in the late pregnancy. The conventional method using the CT dosimetry software cannot take into account the overlap between volumetric sections. Therefore, the conventional method using a 320-row CT unit in a wide-volume mode might result in the underestimation of radiation doses for the fetus and the colon, small intestine, and ovaries.

Three-dimensional ultrasound of the fetus: how does it help?

Three-dimensional ultrasonography (3-D US) was introduced to the field of fetal imaging in the early 1990s. Since then several publications have described potential applications for the diagnosis of congenital malformations as well as organ volumetry. This article reviews basic principles of 3-D US as well as its clinical applicability to prenatal diagnosis of abnormalities involving the face, spine and skeletal system, as well as potential applications of 3-D US for fetal cardiovascular and neuroimaging. Limitations related to motion artifacts, acoustic shadowing and barriers to clinical implementation of 3-D US in clinical practice are addressed.

Perinatal lethal type II osteogenesis imperfecta: a case report

We report a new case of osteogenesis imperfecta (OI) type II which is a perinatal lethal form. First trimester ultrasound didn't identified abnormalities. Second trimester ultrasound showed incurved limbs, narrow chest, with hypomineralization and multiple fractures of ribs and long bones. Parents refused pregnancy termination; they felt that the diagnosis was late. At birth, the newborn presented immediate respiratory distress. Postnatal examination and bone radiography confirmed the diagnosis of OI type IIA. Death occurred on day 25 of life related to respiratory failure.

Stem cell transplantation before birth - a realistic option for treatment of osteogenesis imperfecta?

Osteogenesis imperfecta (OI) is characterized by severe bone deformities, growth retardation and bones that break easily, often from little or no apparent cause. OI is a genetic disorder primarily with defective type I collagen with a wide spectrum of clinical expression. In the more severe cases, it can be diagnosed before birth. Transplantation of mesenchymal stem cells (MSC) has the potential to improve the bone structure and stability, growth and fracture healing. Prenatal and postnatal cell transplantation has been investigated in preclinical and clinical studies of OI and suggests that this procedure is safe and has positive effects. Cell transplantation resulted in improved linear growth, mobility and reduced fracture incidence. However, the effect is transient and for this reason re-transplantation may be needed. So far there is limited experience in this area, and proper studies are required to accurately determine if MSC transplantation is of clinical benefit in the treatment of OI. In this review, we summarize what is currently known in this field.

Association of achondroplasia with Down syndrome: difficulty in prenatal diagnosis by sonographic and 3-D helical computed tomographic analyses

Achondroplasia and Down syndrome are relatively common conditions individually. But co-occurrence of both conditions in the same patient is rare and there have been no reports of fetal analysis of this condition by prenatal sonographic and three-dimensional (3-D) helical computed tomography (CT). Prenatal sonographic findings seen in persons with Down syndrome, such as a thickened nuchal fold, cardiac defects, and echogenic bowel were not found in the patient. A prenatal 3-D helical CT revealed a large head with frontal bossing, metaphyseal flaring of the long bones, and small iliac wings, which suggested achondroplasia. In a case with combination of achondroplasia and Down syndrome, it may be difficult to diagnose the co-occurrence prenatally without typical markers of Down syndrome.

Fetal skeletal computed tomography: when? How? Why?

PURPOSE

To study the additional role of fetal skeletal computed tomography in suspected prenatal bone abnormalities.

MATERIALS AND METHODS

Two centers included in a retrospective study all fetuses who benefited from skeletal computed tomography for a suspected constitutional bone disease or focal dysostosis.

RESULTS

A total of 198 patients were included. CT was performed in 112 patients (56%) for an isolated short femur below the third percentile (group A), in 15 patients (8%) for bowed or fractured femur (group B), in 23 patients (12%) for biometric discrepancy between a short femur and increased head circumference (group C) and in 48 patients (24%) for suspected focal dysostosis (group D). CT was interpreted as normal in 126 cases (64%), i.e. 87% in group A, 0% in group B, 65% in group C and 25% in group D. When including only cases with postnatal or postmortem clinical and/or radiological confirmation was available, CT provided additional and/or more accurate information than ultrasound in 20% of cases in group A, 66% in group B, 30% in group C and 72% in group D. Sixty-seven percent of patients in whom CT was interpreted as normal were lost to follow-up.

CONCLUSION

In isolated short femur, fetal skeletal CT is normal in the great majority of cases although protocolized follow-up of these babies is absolutely compulsory, as a large proportion is lost to follow-up. Fetal skeletal CT can confirm or improve imaging for the suspected diagnosis in suspected focal dysostosis or constitutional bone disease.

Predictive value of fetal lung volume in prenatally diagnosed skeletal dysplasia

OBJECTIVE

Pulmonary hypoplasia is a major cause of death in lethal skeletal dysplasias. We hypothesize that in fetuses with prenatally diagnosed skeletal dysplasia, comparison of observed-to-expected (O/E) lung volume will help predict lethality.

STUDY DESIGN

We conducted a retrospective chart review of patients referred for evaluation of suspected fetal skeletal anomalies. Twenty-three pregnancies were identified with confirmed fetal diagnosis of skeletal dysplasia for which fetal magnetic resonance imaging (MRI) was performed between 21 and 38 weeks of gestation and ultrasound biometry data were available. Femur length to abdominal circumference ratio (FL/AC) and O/E lung volumes were calculated. The association between O/E lung volume, FL/AC, and lethality was measured using logistic regression.

RESULTS

Lethality was significantly associated with O/E lung volume (p = 0.002) and FL/AC (p = 0.0476). Analysis with receiver-operating characteristic curves suggested that O/E lung volume of 47.9% or FL/AC of 0.124 could be useful clinical cutoffs in the prediction of lethality.

CONCLUSION

In fetuses with skeletal dysplasia, fetal MRI-derived O/E lung volume was predictive of lethality. When evaluating a fetal skeletal dysplasia, fetal MRI may be considered in cases for which ultrasound-based lethality prediction is ambiguous or uncertain in order to provide families with the most complete and accurate information.

Nationwide radiation dose survey of computed tomography for fetal skeletal dysplasias

BACKGROUND

Recently, computed tomography (CT) has been used to diagnose fetal skeletal dysplasia. However, no surveys have been conducted to determine the radiation exposure dose and the diagnostic reference level (DRL).

OBJECTIVE

To collect CT dose index volume (CTDIvol) and dose length product (DLP) data from domestic hospitals implementing fetal skeletal 3-D CT and to establish DRLs for Japan.

MATERIALS AND METHODS

Scan data of 125 cases of 20 protocols from 16 hospitals were analyzed. The minimum, first-quartile, median, third-quartile and maximum values of CTDIvol and DLP were determined. The time-dependent change in radiation dose setting in hospitals with three or more cases with scans was also examined.

RESULTS

The minimum, first-quartile, median, third-quartile and maximum CTDIvol values were 2.1, 3.7, 7.7, 11.3 and 23.1 mGy, respectively, and these values for DLP were 69.0, 122.3, 276.8, 382.6 and 1025.6 mGy·cm, respectively. Six of the 12 institutions reduced the dose setting during the implementation period.

CONCLUSIONS

The DRLs of CTDIvol and DLP for fetal CT were 11.3 mGy and 382.6 mGy·cm, respectively. Institutions implementing fetal CT should use these established DRLs as the standard and make an effort to reduce radiation exposure by voluntarily decreasing the dose.

Widening of the femoral proximal diaphysis--metaphysis angle in fetuses with achondroplasia

OBJECTIVES

It has recently been reported that fetuses with achondroplasia have a wider than expected femoral proximal diaphysis-metaphysis angle (femoral angle). The aim of this case-control study was to investigate this finding.

METHODS

Cases with confirmed achondroplasia (n = 6), small-for-gestational-age fetuses (n = 70) and a group of normal fetuses (n = 377) were included in this study. The ultrasound image of the femur was examined by two independent experienced observers blinded to the diagnosis, who measured the femoral angle. These values were converted into multiples of the expected median (MoM), after adjustment for gestational age and femur length. Prevalence of various prenatal ultrasound signs of achondroplasia was determined in affected fetuses. Intra- and interobserver agreement of measurement of femoral angle was assessed using 95% limits of agreement and kappa statistics.

RESULTS

The femoral angle can be measured accurately by ultrasound, and increases with both increasing gestational age and increasing femur length. The femoral angle-MoM was significantly higher in fetuses with achondroplasia than in the control group (1.36 vs 1.00 MoM, P < 0.001) and in the SGA group (1.36 vs 1.04 MoM, P < 0.001). It measured more than 130° in five of the six cases with achondroplasia (83.3%), which was the most consistent finding other than shortening of the long bones.

CONCLUSIONS

The femoral angle is wider in fetuses with achondroplasia. This new ultrasound sign appears promising as an additional discriminatory marker when clinicians are faced with a case of short long bones in the third trimester.

Advances in evaluating the fetal skeleton

In this review, we discuss aspects of the prenatal diagnosis of fetal skeletal malformations, concentrating on the advantages offered by different imaging techniques and the approaches that are of value in evaluating a suspected skeletal dysplasia. We also briefly address the findings in some of the commoner malformations of the fetal skeleton that may be encountered.

The role of ultrasound in the diagnosis of fetal genetic syndromes

The use of ultrasound in the prenatal diagnosis of fetal genetic syndromes is rapidly evolving. Advancing technology and new research findings are aiding in the increased accuracy of ultrasound-based diagnosis in combination with other methods of non-invasive and invasive fetal testing. Ultrasound as a screening tool for aneuploidy and other anomalies is increasingly being used throughout pregnancy, beginning in the first trimester. Given the number of recorded syndromes, it is important to identify patterns and establish a strategy for identifying abnormalities on ultrasound. These syndromes encompass a wide range of causes from viral, substance-linked, chromosomal, and other genetic syndromes. Despite the ability of those experienced in ultrasound, it is important to note that not all fetal genetic syndromes can be identified prenatally, and even common syndromes often have no associated ultrasound findings. Here, we review the role of ultrasound in the diagnosis of fetal genetic syndromes.

Recent advances in sonographic imaging of fetal thoracic structures

Recent ultrasonographic methods applied in the evaluation of fetal thoracic structures and anomalies are presented. Fetal lung volumetric assessment by 3D ultrasonography, analysis of the thoracic wall by 3D-rendered image and 3D skeletal-mode imaging, intrathoracic vessel evaluation by 3D power Doppler ultrasonography, analysis of heart anatomy and abnormalities by 4D spatiotemporal image correlation, identification of normal and abnormal intrathoracic almost isoechogenic structures by volume contrast imaging and evaluation of the heart and great vessels by 3 and 4D inverse mode will be reviewed.

Sonographic markers for early diagnosis of fetal malformations

Fetal malformations are very frequent in industrialized countries. Although advanced maternal age may affect pregnancy outcome adversely, 80%-90% of fetal malformations occur in the absence of a specific risk factor for parents. The only effective approach for prenatal screening is currently represented by an ultrasound scan. However, ultrasound methods present two important limitations: the substantial absence of quantitative parameters and the dependence on the sonographer experience. In recent years, together with the improvement in transducer technology, quantitative and objective sonographic markers highly predictive of fetal malformations have been developed. These markers can be detected at early gestation (11-14 wk) and generally are not pathological in themselves but have an increased incidence in abnormal fetuses. Thus, prenatal ultrasonography during the second trimester of gestation provides a “genetic sonogram”, including, for instance, nuchal translucency, short humeral length, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst, that is used to identify morphological features of fetal Down’s syndrome with a potential sensitivity of more than 90%. Other specific and sensitive markers can be seen in the case of cardiac defects and skeletal anomalies. In the future, sonographic markers could limit even more the use of invasive and dangerous techniques of prenatal diagnosis (amniocentesis, etc.).

Three-dimensional helical computed tomography in prenatal diagnosis of fetal skeletal dysplasia

OBJECTIVES

(1) To study the use and diagnostic value, as a complement to ultrasound, of helical computed tomography (helical CT) to differentiate normal fetuses from cases of skeletal dysplasia; (2) to define the most relevant indications for helical CT; and (3) to evaluate its diagnostic performance with respect to radiological criteria considered discriminatory.

METHODS

This was a retrospective study from 2005 to 2008 in 67 pregnant women who underwent helical CT after 26 weeks of gestation for suspected fetal skeletal dysplasia due to fetal shortened long bones on ultrasound (≤ 10(th) percentile), either alone or associated with other bone abnormalities. The results were compared with pediatric examinations in 41 cases and with fetal autopsy findings after elective termination of pregnancy in the others.

RESULTS

Helical CT had a sensitivity of 82%, specificity of 91% and positive and negative predictive values of 90% and 83%, respectively, for diagnosis of fetal skeletal dysplasia. An etiological diagnosis that had not been suspected at ultrasound was specified in 15% of cases and diagnoses suspected at ultrasound were confirmed in 24% and discounted in 43% of cases. The prevalence of skeletal dysplasia was increased in cases of micromelia < 3(rd) percentile or if there was a combination of bone signs. Helical CT showed 69% sensitivity in identifying individual predefined pathological bone signs which were confirmed on fetal autopsy findings.

CONCLUSION

Helical CT is a key examination, in combination with ultrasound, in the diagnosis of fetal skeletal dysplasia from 26 weeks of gestation. It should be reserved for cases with severe micromelia below the 3(rd) percentile and for those with micromelia ≤ 10(th) percentile associated with another bone sign. A checklist of discriminatory signs is proposed.

Prenatal diagnosis of osteogenesis imperfecta type II by three-dimensional computed tomography: the current state of fetal computed tomography

We report a case of osteogenesis imperfecta (OI) (OMIM166210) type II, in which a prenatal diagnosis was made by three-dimensional computed tomography (3D-CT). Subsequent molecular analysis revealed a recurrent, heterozygous mutation in COL1A2. Fetal CT is a powerful tool for visualizing the fetal skeleton and can provide a definitive diagnosis of fetal skeletal dysplasias; however, whether or not its employment for prenatal diagnosis is warranted in terms of fetal radiation risks remains controversial, both medically and ethically. Based on our experience, we review the current state of fetal CT for the diagnosis of skeletal dysplasias, with a discussion of the relevant literature.

Prenatal diagnosis of fetal skeletal dysplasia with 3D CT

BACKGROUND

Clinical use of 3D CT for fetal skeletal malformations is controversial.

OBJECTIVE

The purpose of this study was to evaluate the efficacy of fetal 3D CT using three protocols with different radiation doses and through comparing findings between fetal CT and conventional postnatal radiographic skeletal survey.

MATERIALS AND METHODS

Seventeen fetuses underwent CT for suspected skeletal dysplasia. A relay of three CT protocols with stepwise dose-reduction were used over the study period. The concordance between the CT diagnosis and the final diagnosis was assessed. Ninety-three radiological findings identifiable on radiographs were compared with CT.

RESULTS

Fetal CT provided the correct diagnosis in all 17 fetuses, the detectability rate of cardinal findings was 93.5 %. In 59 % of the fetuses an US-based diagnosis was changed prenatally due to CT findings. The estimated fetal radiation dose in the final protocol was 3.4 mSv (50 %) of the initial protocol, and this dose reduction did not result in degraded image quality.

CONCLUSION

The capability of fetal CT to delineate the skeleton was almost the same as that of postnatal skeletal survey. The perinatal management was altered due to these more specific CT findings, which aided in counseling and in the management of the pregnancy.