Ultrasonographic and radiologic visualization of the developing embryonic skeleton

Quantitative anatomy of the primary ossification center of the squamous part of temporal bone in the human fetus

Detailed numerical data about the development of primary ossification centers in human fetuses may influence both better evaluation and early detection of skeletal dysplasias, which are associated with delayed development and mineralization of ossification centers. To the best of our knowledge, this is the first report in the medical literature to morphometrically analyze the primary ossification center of the squamous part of temporal bone in human fetuses based on computed tomography imaging. The present study offers a precise quantitative foundation for ossification of the squamous part of temporal bone that may contribute to enhanced prenatal care and improved outcomes for fetuses with inherited cranial defects and skeletodysplasias. The examinations were carried out on 37 human fetuses of both sexes (16 males and 21 females) aged 18-30 weeks of gestation, which had been preserved in 10% neutral formalin solution. Using CT, digital image analysis software, 3D reconstruction and statistical methods, the size of the primary ossification center of the squamous part of temporal bone was evaluated. With neither sex nor laterality differences, the best-fit growth patterns for the primary ossification center of the squamous part of temporal bone was modelled by the linear function: y = -0.7270 + 0.7682 × age ± 1.256 for its vertical diameter, and the four-degree polynomial functions: y = 5.434 + 0.000019 × (age)4 ± 1.617 for its sagittal diameter, y = -4.086 + 0.00029 × (age)4 ± 2.230 for its projection surface area and y = -25.213 + 0.0004 × (age)4 ± 3.563 for its volume. The CT-based numerical data and growth patterns of the primary ossification center of the squamous part of temporal bone may serve as age-specific normative intervals of relevance for gynecologists, obstetricians, pediatricians and radiologists during screening ultrasound scans of fetuses. Our findings for the growing primary ossification center of the squamous part of temporal bone may be conducive in daily clinical practice, while ultrasonically monitoring normal fetal growth and screening for inherited cranial faults and skeletodysplasias.

Thanatophoric dysplasia in nonadherent to antenatal care in low middle income country: a rare case reports

Introduction and importance

Thanatophoric dysplasia is a rare, fatal, and sporadic form of skeletal dysplasia caused by a mutation in fibroblast growth factor receptor 3 (FGFR3). It is characterized by a conical thorax, platyspondyly (flat vertebral bodies), and macrocephaly. This disorder can be diagnosed antenatally as early as 13 weeks of gestation.

Case presentation

The authors reported a case of thanatophoric dysplasia on USG in a 19 year old young consanguineous female in her second trimester of pregnancy. Ultrasound examination showed a clover leaf-shaped skull, a widened anterior fontanel, a coarse and edematous face, a flattened nasal bridge, a short neck, a low set of ears, shortening of both upper and lower limbs with short fingers, bowed thighs and legs, and a relatively narrow thorax.

Clinical discussion

Lung hypoplasia, polyhydramnios, and hydrops in affected individuals lead to a poor prognosis. Hence, timely intervention should be done to avoid a poor prognosis. However, a mix of sonographic, genetic, histological, and autopsy studies are applied to make the most accurate diagnosis.

Conclusion

The authors reported this case due to the rarity of this condition and the need for a systematic and multidisciplinary approach.

Femur development in fetal growth restriction as observed on prenatal magnetic resonance imaging

OBJECTIVE

To investigate human femur development in fetal growth restriction (FGR) by analyzing femur morphometrics and distal epimetaphyseal features on prenatal magnetic resonance imaging (MRI).

METHODS

This was a retrospective study of 111 fetuses (mean gestational age (GA), 27 + 2 weeks (range, 19-35 weeks)) with FGR associated with placental insufficiency without other major abnormalities and 111 GA-matched normal controls. On 1.5-Tesla echoplanar MRI, femur morphometrics, including diaphyseal length, epiphyseal length and epiphyseal width, were assessed. Using a previously reported grading system, epimetaphyseal features, including cartilaginous epiphyseal shape, metaphyseal shape and epiphyseal ossification, were analyzed qualitatively. To compare FGR cases and controls, the paired t-test was used to assess morphometrics, generalized estimating equations were used for epimetaphyseal features and time-to-event analysis was used to assess the visibility of epiphyseal ossification.

RESULTS

There were significant differences in femur morphometrics between FGR cases and controls (all parameters, P < 0.001), with bone shortening observed in FGR. No significant differences were found in the distribution of epimetaphyseal features between FGR cases and controls (epiphyseal shape, P = 0.341; metaphyseal shape, P = 0.782; epiphyseal ossification, P = 0.85). Epiphyseal ossification was visible at a median of 33.6 weeks in FGR cases and at 32.1 weeks in controls (P = 0.008).

CONCLUSIONS

On prenatal MRI, cases with FGR associated with placental insufficiency exhibit diaphyseal and epiphyseal shortening of the femur. However, FGR cases and normal controls share similarly graded distal epimetaphyseal features. Consequently, these features may not be appropriate MRI characteristics for the identification of FGR. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

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.

Body measurements correlation and x-ray imaging of three Hystrix javanica fetuses in different fetal development stages

Hystrix javanica is endemic species in Indonesia. Study about fetal development of Hystrix javanica are very rare because of sample limitation. This study was carried out to describe the morphometrics and x-ray analysis of three fetuses in different stage to give basic information about fetal development of Hystrix javanica. Three fetus samples fixed in Bouin's solution was used in this study. Observation was carried out to identify the characteristic of three fetus samples. This included the pattern of hair, body measurements, body volume, and body weight. X-ray analysis was carried out to know the ossification process in the fetal development. Statistical analysis was carried out using Microsoft 365® Excel program software. Three fetus samples had different specific hair pattern, that was hairless, smooth hairs, and smooth hairs with dense-non dense pattern. Body volume of 1^st, 2^nd, and 3^rd fetus were 23mL, 90mL, and 170mL, respectively. Body weight of 1^st, 2^nd, and 3^rd fetus were 19.5g, 79.22g, and 153.18g, respectively. Pearson's correlation analysis shown strong relationship between total body length, front body length, back body length, horizontal body diameter, vertical body diameter, head length, and head diameter against body volume and body weight of three fetuses. Significant positive correlation was shown between horizontal body diameter, vertical body diameter, and head diameter against body volume and body length with P value < 0.05. Faint radiopaque images showed in the 2^nd fetus sample and strong radiopaque images showed in the 3^rd fetus sample. Radiopaque images were identified in the teeth, cranium, vertebrae, and extremities bones. In this study we concluded that there was a specific hair pattern in different fetal stage. All body measurements have positive correlation with body volume and body weight and x-ray analysis shown that the ossification of the bone was started to happen while the smooth hair was growth.

Two-Dash Line: A New Approach for Prenatal Ultrasound Measurement of Iliac and Ischial Bones to Estimate Gestational Age

OBJECTIVES

There has been a dearth of an accurate and reliable method for the measurement of fetal pelvic bones. In this study, we describe a novel, easy-to-use method for ischial and iliac bone measurement in fetal ultrasound scanning.

METHODS

This prospective cross-sectional study was performed on 1179 pregnant women at 12 to 40 weeks of an uneventful gestation. Pelvic biometric indices, including the length of the ilium and ischium, were measured by a novel and easy method. Then data were analyzed by regression models to develop a formula for gestational age (GA) estimation based on pelvic bones.

RESULTS

The approximate ossification time of the ischium was determined to range between the 13th and 20th gestational weeks. We calculated 3 formulas using linear regression models: formula 1, GA (days) = 92.563 + (11.604 × ischial length); formula 2, GA (days) = 57.006 + (7.819 × iliac length); and formula 3, GA (days) = 65.809 + (5.610 × iliac length) + (3.431 × ischial length).

CONCLUSIONS

The 2-dash line method can contribute to efficient and precise ultrasound measurement of the ilium and ischium in pelvic biometry of the fetus.

Foetal thoracic hypoplasia: concomitant anomalies and neonatal outcomes

The aim of the current study was to determine the frequency of concomitant anomalies in foetal thoracic hypoplasia and the neonatal outcomes of these pregnancies. This retrospective study included 49 cases of foetal thoracic hypoplasia. All of the cases had skeletal system anomalies. Head and face anomalies (36.7%) were the second most frequent accompanying foetal anomaly, and the least common anomaly was genital system anomalies (4.1%). During the follow-ups, 52.6% (n = 10) of the newborns died in the first 24 h of life, 10.5% (n = 2) in the neonatal period and 36.8% (n = 7) in the infantile period.IMPACT STATEMENTWhat is already known on this subject? Foetal thoracic hypoplasias are lethal anomalies due to inadequate pulmonary development. Data on the other system anomalies that accompany foetuses with thoracic hypoplasia are quite limited in the literature. Moreover, even if the lethal course of thoracic hypoplasia is known, the information on how long newborns will survive is unclear.What do the results of this study add? In this study, most of the cases have additional anomalies, especially skeletal system and head-face anomalies. Approximately half of the newborns with thoracic hypoplasia die within the first 24 h.What are the implications of these findings for clinical practice and/or further research? When we need to consult a family considering the outcome of thoracic hypoplasia, this study can be guiding and helpful. On the other hand, the effects of additional anomalies on the prognosis of foetal and neonatal period are not clear. More studies are needed to better understand the prognosis of thoracic hypoplasias.

Anatomical Considerations of Embryology and Development of the Musculoskeletal System: Basic Notions for Musculoskeletal Radiologists

The musculoskeletal (MSK) system begins to form in the third week of intrauterine development. Multiple genes are involved in the complex different processes to form the skeleton, muscles and joints. The embryonic period, from the third to the eighth week of development, is critical for normal development and therefore the time when most structural defects are induced. Many of these defects have a genetic origin, but environmental factors may also play a very important role. This review summarizes the embryology of the different components of the MSK system and their configuration as an organ-system, analyzes the clinical implications resulting from failures in the process of organogenesis, and describes the first approach to diagnosis of skeletal abnormalities using prenatal ultrasound.

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.

Quantitative anatomy of the fused ossification center of the occipital squama in the human fetus

CT-based quantitative analysis of any ossification center in the cranium has not previously been carried out due to the limited availability of human fetal material. Detailed morphometric data on the development of ossification centers in the human fetus may be useful in the early detection of congenital defects. Ossification disorders in the cranium are associated with either a delayed development of ossification centers or their mineralization. These aberrations may result in the formation of accessory skull bones that differ in shape and size, and the incidence of which may be misdiagnosed as, e.g., skull fractures. The study material comprised 37 human fetuses of both sexes (16♂, 21♀) aged 18–30 weeks. Using CT, digital image analysis software, 3D reconstruction and statistical methods, the linear, planar and spatial dimensions of the occipital squama ossification center were measured. The morphometric characteristics of the fused ossification center of the occipital squama show no right—left differences. In relation to gestational age, the ossification center of the occipital squama grows linearly in its right and left vertical diameters, logarithmically in its transverse diameters of both the interparietal and supraoccipital parts and projection surface area, and according to a quadratic function in its volume. The obtained numerical findings of the occipital squama ossification center may be considered age-specific references of relevance in both the estimation of gestational age and the diagnostic process of congenital defects.

Fetal exposure to bisphenols and phthalates and childhood bone mass: a population-based prospective cohort study

BACKGROUND

Exposure to bisphenols and phthalates might influence bone health. We hypothesized that exposure to bisphenols and phthalates during fetal life has persistent effects on bone development.

OBJECTIVES

To analyze the associations of fetal exposure to bisphenols and phthalates with bone health in school-aged children.

METHODS

Among 1,362 mother-child pairs participating in a population-based cohort study, we measured maternal urinary concentrations of bisphenols and phthalates at first, second and third trimester with high performance liquid chromatography electrospray ionization-tandem mass spectrometry. Total body bone mineral density (BMD) and bone area (BA) were measured using dual-energy X-ray absorptiometry (DXA) at 6 and 10 years, and were both used to calculate bone mineral content (BMC) and area-adjusted BMC (aBMC, a measure of volumetric BMD).

RESULTS

Maternal bisphenol concentrations were not associated with childhood bone measures at 6 years. After adjustment for covariates and multiple testing correction, an interquartile range increase in maternal first trimester bisphenol S (BPS) concentrations was associated with lower BMD and aBMC at 10 years (-6.08 (95% confidence interval (CI), -9.97 to -2.19) mg/cm² and -0.12 (95% CI, -0.20 to -0.04) g). Maternal third trimester low molecular weight (LMW) phthalate concentrations were associated with higher aBMC at 6 years whereas, maternal third trimester di-n-octylphthalate (DNOP) concentrations were associated with lower aBMC at 10 years. However, these associations did not remain statistically significant after multiple testing correction.

DISCUSSION

Maternal first trimester BPS concentrations are associated with lower BMD and aBMC in school-aged children. These findings should be considered as hypothesis generating and need further replication and exploration of potential underlying mechanisms.

Morphometric study of the primary ossification center of the frontal squama in the human fetus

PURPOSES

Detailed morphometric data on the development of ossification centers in human fetuses is useful in the early detection of skeletal dysplasias associated with a delayed development of ossification centers and their mineralization. Quantitative analysis of primary ossification centers of cranial bones is sporadic due to limited availability of fetal material.

MATERIAL AND METHODS

The size of the primary ossification center of the frontal squama in 37 human (16 males and 21 females) spontaneously aborted human fetuses aged 18-30 weeks was studied by means of CT, digital-image analysis and statistics.

RESULTS

With neither sex nor laterality differences, the best-fit growth dynamics for the primary ossification center of the frontal squama was modelled by the following functions: y = 13.756 + 0.021 × (age)² ± 0.024 for its vertical diameter, y = 0.956 + 0.956 × age ± 0.823 for its transverse diameter, y = 38.285 + 0.889 × (age)² ± 0.034 for its projection surface area, and y = 90.020 + 1.375 × (age)² ± 11.441 for its volume.

CONCLUSIONS

Our findings for the primary ossification center of the frontal squama may be conducive in monitoring normal fetal growth and screening for inherited faults and anomalies of the skull in human fetuses.

Two novel mutations of COL1A1 in fetal genetic skeletal dysplasia of Chinese

Background

Skeletal disorders, which have great genotypic and phenotypic varieties, are a considerable challenge to differentiate these diseases and provide a definitive prenatal diagnosis or pre‐implantation. The present study aims to identify the causative mutation in two unrelated outbred Han–Chinese families.

Method

Two short‐limb fetuses were referred to our hospital. Genomic DNA was extracted from the amniotic fluid of the short‐limb fetuses and from peripheral blood of their parents. To identify the causative gene, next‐generation‐based target capture sequencing was performed on these two fetuses, followed by Sanger Sequencing in unrelated healthy controls. Segregation analysis of the candidate variant was performed in parents by using Sanger sequencing. The mutations were analyzed by SIFT, PolyPhen and Provean.

Results

We found that fetal genetic skeletal dysplasia was confirmed according to the correlations between genetic mutations and phenotypes in two Chinese families. Targeted next generation sequencing was performed to screen causative mutations in patients. Two novel heterozygous mutations COL1A1 c.1706 G > C (p. G569A) and c.3307 G > A (p. G1103S) were respectively identified. The results suggested that COL1A1 novel mutations were in highly conserved glycine residues present in the Gly‐X‐Y sequence repeats of the triple helical region of the collagen type I α chain, which was responsible for Osteogenesis Imperfecta. The presence of the missense mutation was also confirmed with the Sanger sequence. These two mutations were predicted to be pathogenic by SIFT, PolyPhen and Provean.

Conclusion

Our findings showed that the mutations of COL1A1 may play important roles in fetal genetic skeletal dysplasia in Chinese patients. Exome sequencing enhances the accurate diagnosis in utero then provides appropriate genetic counseling.

Quantitative anatomy of the primary ossification center in the fetal pubis bone

Purposes

Skeletodysplasiae and hereditary dysostoses constitute a group of over 350 disorders of the skeletal system. Knowledge about development of the pubic primary ossification center may be useful in both determining the fetal stage and maturity, and for detecting congenital disorders. The present study was performed to quantitatively examine the pubic primary ossification center with respect to its linear, planar, and volumetric parameters.

Materials and methods

Using methods of computed tomography (CT), digital-image analysis and statistics, the size of the pubic primary ossification center in 33 spontaneously aborted human fetuses (18 males and 15 females) aged 22–30 weeks was studied.

Results

With no sex and laterality differences, the best-fit growth dynamics for the pubic primary ossification center was modeled by the following functions: y = − 13.694 + 0.728 × age ± 0.356 for its sagittal diameter, y = − 3.350 + 0.218 × age ± 0.159 for its vertical diameter, y = − 61.415 + 2.828 × age ± 1.519 for its projection surface area, and y = − 65.801 + 3.173 × age ± 2.149 for its volume.

Conclusions

The size of the pubic primary ossification center shows neither sex nor laterality differences. The growth dynamics of the vertical and sagittal diameters, projection surface area, and volume of the pubic ossification centers follow proportionately to fetal age. The obtained numerical findings of the pubic ossification center are considered age-specific reference data with clinical implications in the diagnostics of congenital defects.

Morphometric study of the primary ossification center of the fibular shaft in the human fetus

PURPOSES

Precise morphometric data on the development of ossification centers in human fetuses may be useful in the early detection of skeletal dysplasias associated with delayed ossification center development and mineralization. The present study was performed to quantitatively examine the primary ossification center of the fibular shaft with respect to its linear, planar and volumetric parameters.

MATERIALS AND METHODS

Using methods of CT, digital-image analysis (Osirix 3.9 MD) and statistics (Student's t-test, Shapiro-Wilk, Fisher's test, Tukey's test, Kruskal-Wallis test, regression analysis), the size of the primary ossification center of the fibular shaft in 47 spontaneously aborted human fetuses (25 ♂ and 22 ♀) aged 17-30 weeks was studied. In each fetus, the assessment of linear dimensions (length, transverse diameters for: proximal end, middle part and distal end), projection surface area and volume of the fibular shaft ossification center was carried out.

RESULTS

With no sex and laterality differences, the best fit growth dynamics for the primary ossification center of the fibular shaft was modelled by the following functions: y = - 13.241 + 1.567 × age ± 1.556 (R2 = 0.94) for its length, y = - 0.091 + 0.063 × age ± 0.073 (R2 = 0.92) for its proximal transverse diameter, y = - 1.201 + 0.717 × ln(age) ± 0.054 (R2 = 0.83) for its middle transverse diameter, y = - 2.956 + 1.532 × ln(age) ± 0.090 (R2 = 0.89) for its distal transverse diameter, y = - 69.038 + 4.699 × age ± 4.055 (R2 = 0.95) for its projection surface area, and y = - 126.374 + 9.462 × age ± 8.845 (R2 = 0.94) for its volume.

CONCLUSIONS

The ossification center in the fibular shaft follows linear functions with respect to its length, proximal transverse diameter, projection surface area and volume, and natural logarithmic functions with respect to its middle and distal transverse diameters. The obtained morphometric data of the fibular shaft ossification center is considered normative for their respective prenatal weeks and may be of relevance in both the estimation of fetal age and the ultrasound diagnostics of congenital defects.

The primary ossification of the human fetal ischium: CT, digital-image analysis, and statistics

Purposes

Details concerning the normal growth of the pelvic girdle in the fetus are of importance in the early detection of congenital defects. This study was executed to quantitatively evaluate the primary ossification center of the ischium with relation to its linear, planar and volumetric parameters.

Materials and methods

Using methods of CT, digital-image analysis, and statistics, geometrical dimensions of the ischium’s primary ossification center in 42 spontaneously aborted human fetuses (21 ♂ and 21 ♀) aged 18–30 weeks were calculated.

Results

With no sex and laterality differences, the best fit growth dynamics for the ischium’s primary ossification center were displayed by the following functions: y = − 10.045 + 0.742 × age ± 0.013 (R² = 0.97) for its vertical diameter, y = − 5.212 + 0.385 × age ± 0.008 (R² = 0.97) for its sagittal diameter, y = − 36.401 + 0.122 × (age)² ± 45.534 (R² = 0.96) for its projection surface area, and y = − 1052.840 + 368.470 × ln(age) ± 12.705 (R² = 0.91) for its volume.

Conclusions

Neither male–female nor right–left differences are found for any of the morphometric parameters of the ischium’s primary ossification center. With relation to fetal ages in weeks, the ischium’s primary ossification center grows proportionately in vertical and sagittal diameters, second-degree polynomially in projection surface area, and logarithmically in volume. The quantitative findings of the ischium’s primary ossification center are considered age-specific reference data of relevance in the diagnostics of innate defects.

Detection of structural abnormalities in the first trimester using ultrasound

During the past 25 years, embryonic and early fetal ultrasound and diagnosis have increasingly gained attention in pregnancy care. Modern high-frequency ultrasound transducers make it possible to obtain detailed images of the early conceptus and its organs, and thus move part of the anatomy and anomaly scan from the second to the first trimester. Today, detection of embryonic and fetal structural abnormalities in the first trimester has frequently been reported. One has to distinguish between diagnosis during the early period until about 10 weeks when the embryo or early fetus is small and transvaginal ultrasound is applied, and diagnosis during the late period at the nuchal translucency screening, usually carried out using transabdominal ultrasound. Early first-trimester abnormalities are often diagnosed by chance on clinical indications, whereas late first-trimester diagnoses are the result of systematic screening using ultrasound markers.

Skeletal development on fetal magnetic resonance imaging

Prenatal magnetic resonance imaging (MRI) is being increasingly used, in addition to standard ultrasound, for the diagnosis of congenital diseases beyond the central nervous system. Previous studies have demonstrated that MRI may be useful for the in utero visualization of spinal dysraphism and for differentiating between isolated and complex skeletal disorders with associated abnormalities. More recently, attention has focused on the visualization of the human fetal skeleton for the delineation of normal and pathological development of skeletal structures. On 1.5 T, in particular, echoplanar imaging enables the delineation of various epimetaphyseal structures and morphometric measurements of the fetal long bones from 18 gestational weeks until term. This information gathered from prenatal MRI might be helpful in the diagnosis of focal bone abnormalities and generalized skeletal disorders, such as bone dysplasias. Further clinical research, along with the refinement of the newest techniques, will enable expansion of the preliminary findings and help in determining the impact of fetal magnetic resonance bone imaging in the routine clinical setting. This review summarizes the current data in the literature and the authors' clinical experience with the magnetic resonance visualization of the developing fetal skeleton and also comments on the potential future applications of this technique.

Human long bone development in vivo: analysis of the distal femoral epimetaphysis on MR images of fetuses

PURPOSE

To investigate human long bone development in vivo by analyzing distal femoral epimetaphyseal structures and bone morphometrics on magnetic resonance (MR) images of fetuses.

MATERIALS AND METHODS

An institutional review board approved this retrospective study, and informed consent was waived. Included were 272 MR imaging examinations (April 2004-July 2011) in 253 fetuses with a mean gestational age (GA) of 26 weeks 6 days (range, 19 weeks 2 days to 35 weeks 6 days) without known musculoskeletal abnormalities. Two independent readers qualitatively analyzed epiphyseal and metaphyseal shape, secondary ossification, and the perichondrium on 1.5-T echo-planar MR images and correlated the results with the GA that was derived from previous fetal ultrasonography (US). Diaphyseal and epiphyseal morphometric measurements were correlated with GA by means of the Pearson correlation and linear regression. MR imaging measurements of diaphyseal length and US normative values were compared graphically. Interreader agreement analysis was performed with weighted κ statistics and the intraclass correlation coefficient.

RESULTS

With advancing GA, the epiphyseal shape changed from spherical (r(2) = 0.664) to hemispherical with a notch (r(2) = 0.804), and the metaphyseal shape changed from flat (r(2) = 0.766) to clearly undulated (r(2) = 0.669). Secondary ossification (r(2) = 0.777) was not observed until 25 weeks 3 days. The perichondrium decreased (r(2) = 0.684) from 20 weeks onward. Correlation coefficients were 0.897 for diaphyseal length, 0.738 for epiphyseal length, and 0.801 for epiphyseal width with respect to GA. The range of measurements of diaphyseal length was larger than that of the reported US normative values. Interreader agreement was good for bone morphometrics (intraclass correlation coefficient, 0.906-0.976), and moderate for bone characteristics (weighted κ, 0.448-0.848).

CONCLUSION

Prenatal MR imaging allows visualization of human bone development in vivo by means of epimetaphyseal characteristics and bone morphometrics.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13112441/-/DC1.

Detailed ultrasound screening in the second trimester: pictorial essay of normal fetal anatomy

Today, ultrasound is the main diagnostic tool in the prenatal detection of congenital abnormalities. Therefore, ultrasound examination should be offered to all pregnant women. A detailed sonographic examination of the fetus is usually performed between 18 and 22 weeks of pregnancy. The accurate recognition of normal fetal anatomy is very important for the detection of both minor and major defects. The purpose of this pictorial essay is to show fetal anatomic structures, which have to be examined between the 18(th) and 22(nd) weeks of pregnancy, and present their standard measurements systematically and thoroughly in accordance with sonographically obtained ideal sections.

The skeleton and musculature on foetal MRI

BACKGROUND: Magnetic resonance imaging (MRI) is used as an adjunct to ultrasound in prenatal imaging, the latter being the standard technique in obstetrical medicine. METHODS: Initial results demonstrate the ability to visualise the foetal skeleton and muscles on MRI, and highlight the potentially useful applications for foetal MRI, which has significantly profited from innovations in sequence technology. Echoplanar imaging, thick-slab T2-weighted (w) imaging, and dynamic sequences are techniques complementary to classical T2-w imaging. RESULTS: Recent study data indicate that foetal MRI may be useful in the imaging of spinal dysraphism and in differentiating between isolated and complex skeletal deformities with associated congenital malformations, which might have an impact on pre- and postnatal management. CONCLUSION: More research and technical refinement will be necessary to investigate normal human skeletal development and to identify MR imaging characteristics of skeletal abnormalities.

Guidelines for the prenatal diagnosis of fetal skeletal dysplasias

The osteochondrodysplasias, or skeletal dysplasias are a genetically heterogeneous group of over 350 distinct disorders, and many of them can present in the prenatal period as demonstrated by ultrasound. Differentiating these disorders in the prenatal period can be challenging because they are rare and many of the ultrasound findings are not necessarily pathognomic for a specific disorder. However, differentiating known lethal disorders from nonlethal disorders, providing differential diagnoses before delivery, determining postdelivery management plans and ultimately determining accurate recurrences risks to the at-risk couples improves patient care. These guidelines provide an approach to a fetus suspected of manifesting a skeletal dysplasia.

Evaluation of prenatal-onset osteochondrodysplasias by ultrasonography: a retrospective and prospective analysis

The osteochondrodysplasias or skeletal dysplasias are a heterogenous group of over 350 distinct disorders of skeletogenesis. Many manifest in the prenatal period, making them amenable to ultrasound prenatal diagnosis. A retrospective analysis evaluated 1,500 cases referred to the International Skeletal Dysplasia Registry (ISDR) to determine the relative frequency of specific osteochondrodysplasias and correlation of ultrasound versus radiographic diagnoses for these disorders. Within the retrospective cohort of 1,500 cases, 85% of the referred cases represented well-defined skeletal dysplasias, and the other 15% of cases were a mixture of genetic syndromes and probable early-onset intrauterine growth restriction. The three most common prenatal-onset skeletal dysplasias were osteogenesis imperfecta type 2, thanatophoric dysplasia and achondrogenesis 2, accounting for almost 40% of the cases. In a prospective analysis of 500 cases using a standardized ultrasound approach to the evaluation of these disorders, the relative frequencies of osteogenesis imperfecta type 2, thanatophoric dysplasia and achondrogenesis 2 were similar to the retrospective analysis. This study details the relative frequencies of specific prenatal-onset osteochondrodysplasias, their heterogeneity of prenatal-onset skeletal disorders and provides a standardized prenatal ultrasound approach to these disorders which should aid in the prenatal diagnosis of fetuses suspected of manifesting skeletal dysplasias.

First Trimester Ultrasound Diagnosis of Lethal Multiple Pterygium Syndrome

OBJECTIVE

Diagnosis of lethal multiple pterygium syndrome in the first trimester of pregnancy.

METHODS

A 38-year-old woman attended our ultrasound (US) clinic at 11.2 weeks gestation. She has had two previous stillbirths affected by lethal multiple pterygium syndrome. Transabdominal and transvaginal US were performed and identified a recurrence. Autopsy findings are compared to the fetal US findings.

RESULTS

Fetal US showed a markedly increased nuchal translucency, fixed flexion deformities of the elbows and knees bilaterally, cutaneous webs across both elbow joints and absent fetal movements. The patient decided to terminate the pregnancy and a D&C was performed. Pathology of intact fetal parts showed flexion deformity of the right elbow with a cutaneous web, and ulnar deviation of the right wrist.

CONCLUSION

Increased nuchal translucency, absent limb movements, multiple joint contractures and cutaneous webs on US allowed the diagnosis of lethal multiple pterygium syndromes in the first trimester of pregnancy.

Fetal spine ossification: the gender and individual differences illustrated by ultrasonography

The spatial and temporal pattern of manifestation of ossification nuclei of the spinal column in fetal life have been well established by histologic and radiologic studies. Sonographic evaluation of the fetal spine depends on visualization of the ossification centers, but the sequence of development of ossification centers in the vertebral column obtained by embryologists and sonographers and radiology are conflicting. We carried out a longitudinal study to establish the ultrasonographic appearance and timing of development of primary ossification centers of the fetal spine in the first and second trimesters of pregnancy. A total of 80 mothers were evaluated during their pregnancy with two echographic controls; in the first trimester, the spine length was measured and, in the second trimester of pregnancy, the timing of ossification of the bodies and neural arches of sacral vertebrae and the difference in appearance between the female and male genders were evaluated. Spinal length measurements obtained in the first trimester and percentage of detection of sacral vertebral structures increased progressively with a regular pattern in relation to gestational age. Spinal length at first ultrasound examination was slightly correlated with time of appearance of sacral bodies and arches. Ossification timing was significantly earlier in females than in males. The study has attempted to improve our understanding of the sonographic detection of the spinal ossification. Data presented give some further information on the stages of appearance of sacral vertebrae body centers during intrauterine development. Differences between genders and interindividual variations in ossification timing were observed at a very early stage of development. This could be of value when fetal growth is evaluated. Moreover, further knowledge of spinal development may be useful for early diagnosis of spinal abnormalities and for fetal biometrics.

Prenatal diagnosis of musculoskeletal anomalies

Musculoskeletal anomalies are not uncommon in prenatal life. They can be either sporadic or part of chromosomal syndromes causing prenatal morbidity and mortality. The prenatal diagnosis of musculoskeletal anomalies is based on information assembled from various imaging modalities and from biochemical and genetic workups. The prenatal diagnosis can serve as a prognostic tool and in counseling the parents. Among the imaging methods, ultrasonography is the most popular and cost effective in observing and following fetal development from the very early stages of gestation. Transvaginal sonography can detect and identify most of the normal and the specific pathologic changes very close to the stage of their embryogenic development. From a practical point of view, early detailed transvaginal sonography screening at 14 to 15 weeks of gestation is very useful while late detection at 20 to 23 weeks of gestation may provide some additional information in low-risk pregnancies. Very early screening, even during the ninth week, may be indicated in high-risk pregnancies. Additional genetic counseling is recommended when abnormal findings are suspected. We summarize the diagnostic approach and the information available for the most common musculoskeletal anomalies.

Detection of fetal structural abnormalities with US during early pregnancy

Ultrasonography (US) is performed during early pregnancy for dating, determination of the number of fetuses, assessment of early complications, and increasingly for evaluation of the fetus, including measurement of the thickness of the nuchal translucency (NT). Measurement of NT thickness between 11 and 14 weeks gestation, combined with maternal age and maternal serum biochemistry, can be an effective method of screening for trisomy 21 and other chromosomal abnormalities. Furthermore, an increased NT thickness in the presence of a normal karyotype is associated with an increased frequency of structural defects and genetic syndromes. Therefore, this finding is an indication for a more detailed anatomic survey of the fetus. Besides nuchal abnormalities, a wide range of other congenital anomalies can be diagnosed with US at 11-14 weeks gestation, including defects of the central nervous system, heart, anterior abdominal wall, urinary tract, and skeleton. The anatomic survey can be performed with a standardized protocol by using transabdominal US and, when necessary, transvaginal US. A thorough knowledge of the US features of normal fetal development is necessary to avoid potential diagnostic pitfalls.

Hypophosphatasia associated with increased nuchal translucency: a report of two affected pregnancies

Perinatal hypophosphatasia is a lethal autosomal recessive skeletal abnormality with a birth prevalence of about 1 per 100 000. It is characterized by deficiency of the tissue-nonspecific isoenzyme of alkaline phosphatase causing abnormal bone mineralization. In the two affected fetuses from the same family ultrasound examination at 14 and 12 weeks, respectively, demonstrated increased nuchal translucency thickness, hypomineralization of the skull and spine, narrowing of the chest and shortening of the limbs.

Spine length measurement in the first trimester of pregnancy

OBJECTIVES

The aim of the study was to evaluate spine length as an indicator of skeletal growth in the first trimester of pregnancy and to provide a nomogram of spine length at the end of the first trimester of pregnancy.

METHODS

The study was carried out on 420 single pregnancies, at gestational ages ranging from 11 to 14 weeks, using high-resolution transabdominal echography. Biparietal diameter and crown-rump length (CRL) were measured to date the pregnancy. Using the same scanning plane used to measure CRL, the whole spine length in antero-dorsal position can be visualized as a double hyperechoic line from 10 weeks of gestation onwards. Spine length was measured three times by one observer and the mean of the three measurements was considered as definitive. Forty fetuses had multiple measurements for interobserver and intraobserver error analysis.

RESULTS

Linear relationship between spine length, and gestational age, biparietal diameter and CRL were demonstrated. Spine length (millimetres) as a function of gestational age (days) was expressed by the regression equation: spine length = 1.09 x (gestational age in days) -60.56, with a determination coefficient of R(2) = 0.744. Spine length ranged from 21.5 mm at 11 weeks to 41.9 mm at 14 weeks.

CONCLUSION

The data obtained showed that spine length increased progressively from the end of the first trimester to the beginning of the second. A high correlation between spine length, gestational age, biparietal diameter, and CRL was observed. Spine length measurement could therefore be considered a good indicator of fetal growth.

Three-dimensional sonographic visualization of fetal skeleton in the second trimester of pregnancy

PURPOSE

To demonstrate the potential of using three-dimensional (3D) sonography to reveal anomalies of fetal skeleton.

MATERIALS AND METHODS

Forty-two normal fetuses and 3 anencephalic fetuses from 14 to 27 weeks' gestation were studied with a specially developed abdominal 3D transducer (3.5 MHz). This imaging system provided conventional two-dimensional (2D) sonographic images and also generated within seconds high-quality 3D images in the surface and transparent mode with no need for an external workstation.

RESULTS

Using this imaging system, we obtained 2D and 3D images of fetal skeleton (skull, scapula, spine, rib, humerus, ulna/radius, pelvis, femur, and tibia/fibula) at two gestational ages. The percentages of fetal skeletal visualization at less than 20 weeks of gestation using 3D sonography were 78-100%, whereas those with 2D sonography were all 100%. The percentages of skeletal structures revealed after 20 weeks' gestation using 3D sonography were 82-100%, whereas those with 2D sonography were all 100%. We found no significant differences in detection rates of the fetal skeleton between 2D and 3D sonography. However, 3D sonographic images generally provided a more comprehensive view of the fetal skeleton than did conventional 2D sonography. In 2 cases with anencephaly, 3D sonography clearly revealed the defect of cranium.

CONCLUSION

The new 3D sonographic technology can generate within seconds high-quality 3D images of the fetal skeleton. The 3D technology seems to perform at least as well as conventional 2D sonography. Our results suggest that 3D sonography has the potential to supplement 2D sonography and might be useful in identifying malformations of the fetal skeleton and chromosomal abnormalities in utero.

The axolotl as an animal model for the comparison of 3-D ultrasound with plain film radiography

We assessed the usefulness of an animal model, the axolotl (Ambystoma mexicanum), in comparing 3-D ultrasound (3-D US) and plain film radiographs. Hindlimbs were amputated from 5 animals, at either the zeugopodial or stylopodial level, and each regenerating limb was imaged 16 times with 3-D US and 14 times with plain film X ray over 315 days. US images were acquired with a Siemens Sonoline Versa Pro and a 10-MHz linear array transducer. For 3-D US images, the probe was translated in a motor-driven linear stage while images were digitized. The regenerating tibia and fibula bones were detected on 3-D US an average of 37 days earlier than on plain film radiography, and regenerating phalangeal bones were detected on 3-D US an average of 18 days earlier. After 120 days, both imaging modalities consistently showed the bones. The average bone growth rates for the tibia and fibula were 0.019 +/- 0.001 mm/day and 0.019 +/- 0.001 mm/day, respectively.

Novel fetal imaging techniques

Fetal imaging technology is evolving rapidly, and new techniques are being evaluated to establish their role in the assessment of the fetus. It is essential that these methods of fetal imaging are carefully assessed to ascertain if they provide additional information to assist in the clarification or understanding of fetal disease states that is not already provided by current conventional imaging techniques.