Embryonic morphological development is delayed in pregnancies ending in a spontaneous miscarriage.

STUDY QUESTION: Is there a difference in embryonic morphological development between ongoing pregnancies and live pregnancies ending in a miscarriage? SUMMARY ANSWER: Embryonic morphological development, assessed by the Carnegie stages, is delayed in live pregnancies ending in a miscarriage compared to ongoing pregnancies. WHAT IS KNOWN ALREADY: Pregnancies ending in a miscarriage tend to have smaller embryos and slower heart rates. STUDY DESIGN, SIZE, DURATION: Between 2010 and 2018, 644 women with singleton pregnancies, in the periconception period, were enrolled in a prospective cohort study with follow up until 1 year after delivery. A miscarriage was registered as a non-viable pregnancy before 22 weeks gestational age, defined by an absent heartbeat by ultrasound for a previously reported live pregnancy. PARTICIPANTS/MATERIALS, SETTING, METHODS: Pregnant women with live singleton pregnancies were included and serial three-dimensional transvaginal ultrasound scans were performed. Embryonic morphological development was assessed by the Carnegie developmental stages and evaluated using virtual reality techniques. The embryonic morphology was compared to clinically used growth parameters (i.e. crown-rump length (CRL) and embryonic volume (EV)). Linear mixed models were used to evaluate the association between miscarriage and the Carnegie stages. Logistic regression with generalized estimating equations was used to calculate the odds of a miscarriage after a delay in Carnegie stages. Adjustments were made for potential confounders or covariates and include age, parity, and smoking status. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 611 ongoing pregnancies and 33 pregnancies ending in a miscarriage were included between 7 + 0 and 10 + 3 weeks gestational age, resulting in 1127 assigned Carnegie stages for evaluation. Compared to an ongoing pregnancy, a pregnancy ending in a miscarriage is associated with a lower Carnegie stage (ßCarnegie = -0.824, 95% CI -1.190; -0.458, P < 0.001). A live embryo of a pregnancy ending in a miscarriage will reach the final Carnegie stage with a delay of 4.0 days compared to an ongoing pregnancy. A pregnancy ending in a miscarriage is associated with a smaller CRL (ßCRL = -0.120, 95% CI -0.240; -0.001, P = 0.049) and EV (ßEV = -0.060, 95% CI -0.112; -0.007, P = 0.027). The delay in Carnegie stage increases the odds of a miscarriage by 1.5% per delayed Carnegie stage (ORCarnegie = 1.015, 95% CI 1.002; 1.028, P = 0.028). LIMITATIONS, REASONS FOR CAUTION: We included a relatively small number of pregnancies ending in a miscarriage from a study population that is recruited from a tertiary referral centre. Furthermore, results of genetic testing on the products of the miscarriages or information on the karyotype of the parents were not available. WIDER IMPLICATIONS OF THE FINDINGS: Embryonic morphological development, assessed by the Carnegie stages, is delayed in live pregnancies ending in a miscarriage. In the future, embryonic morphology may be used to estimate the likelihood of a pregnancy continuing to the delivery of a healthy baby. This is of crucial importance for all women but in particular for those at risk of a recurrent pregnancy loss. As part of supportive care, both women and their partners may benefit from information on the prospective outcome of the pregnancy and the timely identification of a miscarriage. STUDY FUNDING/COMPETING INTEREST(S): The work was funded by the Department of Obstetrics and Gynaecology, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands. The authors declare no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

Comparison of postmortem whole-body contrast-enhanced microfocus computed tomography and high-field magnetic resonance imaging of human fetuses.

OBJECTIVE: Although fetal autopsy is generally recommended to confirm or refute the antemortem diagnosis, parental acceptance of the procedure has fallen over time, mainly due to its invasiveness. Contrast-enhanced microfocus CT (micro-CT) and high-field magnetic resonance imaging (HF-MRI, ≥ 3 Tesla) have both been suggested as non-invasive alternatives to conventional fetal autopsy for fetuses < 20 weeks of gestation. The aim of this study was to compare these two modalities in postmortem whole-body fetal imaging. METHODS: In this study, the imaging process and quality of micro-CT and HF-MRI were compared using both qualitative and quantitative assessments. For the qualitative evaluation, fetal anatomy experts scored 56 HF-MRI and 56 micro-CT images of four human fetuses aged 13-18 gestational weeks on two components: overall image quality and the ability to recognize and assess 21 anatomical structures. For the quantitative evaluation, participants segmented manually three organs with increasing complexity to assess interobserver variability. In addition, the signal-to-noise and contrast-to-noise ratios of five major organs were determined. RESULTS: Both imaging techniques were able to reach submillimeter voxel size. The highest resolution of micro-CT was 22 µm (isotropic), while the highest resolution of HF-MRI was 137 µm (isotropic). The qualitative image assessment form was sent to 45 fetal anatomy experts, of whom 36 (80%) responded. It was observed that micro-CT scored higher on all components of the qualitative assessment compared with HF-MRI. In addition, the quantitative assessment showed that micro-CT had lower interobserver variability and higher signal-to-noise and contrast-to-noise ratios. CONCLUSIONS: Our findings show that micro-CT outperforms HF-MRI in postmortem whole-body fetal imaging in terms of both quantitative and qualitative outcomes. Combined, these findings suggest that the ability to extract diagnostic information is greater when assessing micro-CT compared with HF-MRI images. We, therefore, believe that micro-CT is the preferred imaging modality as an alternative to conventional fetal autopsy for early gestation and is an indispensable tool in postmortem imaging services. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Reducing soft-tissue shrinkage artefacts caused by staining with Lugol's solution.

Diffusible iodine-based contrast-enhanced computed tomography (diceCT) is progressively used in clinical and morphological research to study developmental anatomy. Lugol's solution (Lugol) has gained interest as an effective contrast agent; however, usage is limited due to extensive soft-tissue shrinkage. The mechanism of Lugol-induced shrinkage and how to prevent it is largely unknown, hampering applications of Lugol in clinical or forensic cases where tissue shrinkage can lead to erroneous diagnostic conclusions. Shrinkage was suggested to be due to an osmotic imbalance between tissue and solution. Pilot experiments pointed to acidification of Lugol, but the relation of acidification and tissue shrinkage was not evaluated. In this study, we analyzed the relation between tissue shrinkage, osmolarity and acidification of the solution during staining. Changes in tissue volume were measured on 2D-segmented magnetic resonance and diceCT images using AMIRA software. Partial correlation and stepwise regression analysis showed that acidification of Lugol is the main cause of tissue shrinkage. To prevent acidification, we developed a buffered Lugol's solution (B-Lugol) and showed that stabilizing its pH almost completely prevented shrinkage without affecting staining. Changing from Lugol to B-Lugol is a major improvement for clinical and morphological research and only requires a minor adaptation of the staining protocol.

Novel imaging techniques to study postmortem human fetal anatomy: a systematic review on microfocus-CT and ultra-high-field MRI.

BACKGROUND: MRI and CT have been extensively used to study fetal anatomy for research and diagnostic purposes, enabling minimally invasive autopsy and giving insight in human fetal development. Novel (contrast-enhanced) microfocus CT (micro-CT) and ultra-high-field (≥ 7.0 T) MRI (UHF-MRI) techniques now enable micron-level resolution that combats the disadvantages of low-field MRI and conventional CT. Thereby, they might be suitable to study fetal anatomy in high detail and, in time, contribute to the postmortem diagnosis of fetal conditions. OBJECTIVES: (1) To systematically examine the usability of micro-CT and UHF-MRI to study postmortem human fetal anatomy, and (2) to analyze factors that govern success at each step of the specimen preparation and imaging. METHOD: MEDLINE and EMBASE were systematically searched to identify publications on fetal imaging by micro-CT or UHF-MRI. Scanning protocols were summarized and best practices concerning specimen preparation and imaging were enumerated. RESULTS: Thirty-two publications reporting on micro-CT and UHF-MRI were included. The majority of the publications focused on imaging organs separately and seven publications focused on whole body imaging, demonstrating the possibility of visualization of small anatomical structures with a resolution well below 100 µm. When imaging soft tissues by micro-CT, the fetus should be stained by immersion in Lugol's staining solution. CONCLUSION: Micro-CT and UHF-MRI are both excellent imaging techniques to provide detailed images of gross anatomy of human fetuses. The present study offers an overview of the current best practices when using micro-CT and/or UHF-MRI to study fetal anatomy for clinical and research purposes. KEY POINTS: • Micro-CT and UHF-MRI can both be used to study postmortem human fetal anatomy for clinical and research purposes. • Micro-CT enables high-resolution imaging of fetal specimens in relatively short scanning time. However, tissue staining using a contrast solution is necessary to enable soft-tissue visualization. • UHF-MRI enables high-resolution imaging of fetal specimens, without the necessity of prior staining, but with the drawback of long scanning time.

The Pronephros; a Fresh Perspective.

Contemporary papers and book chapters on nephrology open with the assumption that human kidney development passes through three morphological stages: pronephros, mesonephros, and metanephros. Current knowledge of the human pronephros, however, appears to be based on only a hand full of human specimens. The ongoing use of variations in the definition of a pronephros hampers the interpretation of study results. Because of the increased interest in the anamniote pronephros as a genetic model for kidney organogenesis we aimed to provide an overview of the literature concerning kidney development and to clarify the existence of a pronephros in human embryos. We performed an extensive literature survey regarding vertebrate renal morphology and we investigated histological sections of human embryos between 2 and 8 weeks of development. To facilitate better understanding of the literature about kidney development, a referenced glossary with short definitions was composed. The most striking difference between pronephros versus meso- and metanephros is found in nephron architecture. The pronephros consists exclusively of non-integrated nephrons with external glomeruli, whereas meso- and metanephros are composed of integrated nephrons with internal glomeruli. Animals whose embryos have comparatively little yolk at their disposal and hence have a free-swimming larval stage do develop a pronephros that is dedicated to survival in aquatic environments. Species in which embryos do not have a free-swimming larval stage have embryos that are supplied with a large amount of yolk or that develop within the body of the parent. In those species the pronephros is usually absent, incompletely developed, and apparently functionless. Non-integrated nephrons were not identified in histological sections of human embryos. Therefore, we conclude that a true pronephros is not detectable in human embryos although the most cranial part of the amniote excretory organ is often confusingly referred to as pronephros. The term pronephros should be avoided in amniotes unless all elements for a functional pronephros are undeniably present.