Placental Imaging: Normal Appearance with Review of Pathologic Findings

Magnetic Resonance Imaging-Based Radiomics Nomogram to Predict Intraoperative Hemorrhage of Placenta Previa

OBJECTIVE

 Placenta previa (PP) is associated with intraoperative and postpartum hemorrhage, increased maternal morbidity and mortality. We aimed to develop a magnetic resonance imaging (MRI)-based nomogram to preoperative prediction of intraoperative hemorrhage (IPH) for PP.

STUDY DESIGN

 A total of 125 PP pregnant women were divided into a training set (n = 80) and a validation set (n = 45). An MRI-based model was built for the classification of patients into IPH and non-IPH groups in a training set and a validation set. Multivariate nomograms were built according to radiomics features. Receiver operating characteristic (ROC) curve was used to assess the model. Predictive accuracy of nomogram were assessed by calibration plots and decision curve analysis.

RESULTS

 In multivariate analysis, placenta position, placenta thickness, cervical blood sinus, and placental signals in the cervix were significantly independent predictors for IPH (all ps < 0.05). The MRI-based nomogram showed favorable discrimination between IPH and non-IPH groups. The calibration curve showed good agreement between the estimated and the actual probability of IPH. Decision curve analysis also showed a high clinical benefit across a wide range of probability thresholds. Area under the ROC curve was 0.918 (95% confidence interval [CI]: 0.857-0.979) in the training set and 0.866 (95% CI: 0.748-0.985) in the validation set by the combination of four MRI features.

CONCLUSION

 The MRI-based nomograms might be a useful tool for the preoperative prediction of IPH outcomes for PP. Our study enables obstetricians to perform adequate preoperative evaluation to reduce blood loss and cesarean hysterectomy.

KEY POINTS

· MRI is an important method for preoperative assessment of the risk of placenta previa.. · MRI-based nomogram can assess the risk of intraoperative bleeding of placenta previa.. · MRI is helpful for more comprehensive evaluation of placenta previa and adequate preoperative preparation..

Imaging of Antepartum and Postpartum Hemorrhage

Severe obstetric hemorrhage is a leading cause of maternal mortality and morbidity worldwide. Major hemorrhage in the antepartum period presents potential risks for both the mother and the fetus. Similarly, postpartum hemorrhage (PPH) accounts for up to a quarter of maternal deaths worldwide. Potential causes of severe antepartum hemorrhage that radiologists should be familiar with include placental abruption, placenta previa, placenta accreta spectrum disorders, and vasa previa. Common causes of PPH that the authors discuss include uterine atony, puerperal genital hematomas, uterine rupture and dehiscence, retained products of conception, and vascular anomalies. Bleeding complications unique to or most frequently encountered after cesarean delivery are also enumerated, including entities such as bladder flap hematomas, rectus sheath and subfascial hemorrhage, and infectious complications of endometritis and uterine dehiscence. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Javitt and Madrazo in this issue.

Use of Photoacoustic Imaging to Study the Effects of Anemia on Placental Oxygen Saturation in Normoxic and Hypoxic Conditions

We aimed to evaluate fetal and placental oxygen saturation (sO2) in anemic and non-anemic pregnant rats throughout gestation using photoacoustic imaging (PAI). Female Sprague-Dawley rats were fed an iron-restricted or iron-replete diet before and during pregnancy. On gestational days 13, 18, and 21, PAI was coupled with high resolution ultrasound to measure oxygenation of the fetus, whole placenta, mesometrial triangle, as well as the maternal and fetal faces of the placenta. PAI was performed in 3D, which allowed sO2 to be measured within an entire region, as well as in 2D, which enabled sO2 measurements in response to a hypoxic event in real time. Both 3D and 2D PAI were performed at varying levels of FiO2 (fraction of inspired oxygen). Iron restriction caused anemia in dams and fetuses, a reduction in fetal body weight, and an increase in placental weight, but overall had minimal effects on sO2. Reductions in FiO2 caused corresponding reductions in sO2 which correlated to the severity of the hypoxic challenge. Regional differences in sO2 were evident within the placenta and between the placenta and fetus. In conclusion, PAI enables non-invasive measurement of sO2 both rapidly and with a high degree of sensitivity. The lack of overt changes in sO2 levels between control and anemic fetuses may suggest reduced oxygen extraction and utilization in the latter group, which could be attributed to compensatory changes in growth and developmental trajectories.

Establishment of a new equation to estimate gestational age in female dogs

The objectives of this study were to propose a statistical model to predict the behaviour of the thickness of the uteroplacental junction as a function of the gestation period in female dogs and to determine the relationship between the thickness of the placenta and gestational age in healthy female dogs whose pregnancies had elapsed without maternal-fetal alterations. Eight Border Collie female dogs were selected, aged 3-6 (4.48 ± 0.89) and weighing 16-22 kg (19.06 ± 1.9 kg). Female dogs with gestational ages from 20 to 62 days were examined weekly using B-mode ultrasonography. Ultrasound measurements of the uteroplacental junction were organized into four distinct groups: GT1 (27-36 days of gestation), GT2 (37-46 days of gestation), GT3 (47-56 days of gestation) and GT4 (57-62 days of gestation). Based on multiple linear regression, a statistical model was proposed to predict the behaviour of the thickness of the uteroplacental junction (y) as a function of the length of gestation (x) in female dogs, where b0 is the intercept (linear coefficient) and bp is the slope of the predictors. The analysis relating GT, age and weight could predict placental thickness and resulted in a statistically significant model [F(1,28) = 153,736; p < .001; R2  = .846], but only that relating the length of pregnancy (β = .92; t = 12.399; p < .001) predicted the thickness of the placenta according to the equation y = b0 + bp.x1 [(thickness in cm) = β -0.3 + 0.019 × (gestation time in days)]. Only in GT4 was there no correlation between placentas within the same pregnancy (p > .05). Based on the close relationship between the development of the uteroplacental junction thickness during pregnancy and gestational age, it is possible to develop a new tool to complement gestational ultrasound evaluation in female dogs. This is important because it allows better placental evaluation in the search for significant alterations that could compromise maternal-fetal health.

Value of placental virtual magnetic resonance elastography and intravoxel incoherent motion-based diffusion and perfusion in predicting adverse outcomes of small-for-gestational-age infants

OBJECTIVE

It is critical to early monitor and manage small-for-gestational age (SGA) infants with truly adverse outcomes not detected by conventional methods. We aimed to explore the value of diffusion-weighted imaging (DWI)-based virtual magnetic resonance elastography (vMRE) and intravoxel incoherent motion (IVIM)-based biexponential and stretched exponential parameters in predicting adverse outcomes of SGA infants.

METHODS

Twenty SGA infants with adverse outcomes and forty without adverse outcomes were included in this prospective study. One DWI-based vMRE parameter [the stiffness value (μdiff)], five IVIM-based parameters [true diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), diffusion distribution coefficient (DDC), and diffusion heterogeneity index (Alpha)] and apparent diffusion coefficient (ADC) were calculated and compared between groups. The predictive efficiency was compared by the logistic regression analysis and receiver operating characteristic curve analysis. The relationship between the μdiff value with gestational age was also evaluated.

RESULTS

The placental μdiff value was remarkably higher, and the f, DDC, and ADC values were considerably lower in the SGA infants with adverse outcomes compared with those without adverse outcomes. The μdiff and f value were predictive risk factors for SGA infants with adverse outcomes. A combined predictive model (μdiff and f) improved the predictive efficacy. Moreover, there was no statistically significant correlation between the placental stiffness value and gestational age.

CONCLUSIONS

Functional MRI parameters to quantify placenta elastography and microcirculation in SGA patients. This might be a useful tool to assess placental function and a vital non-invasive supplement for predicting adverse outcomes of SGA infants.

CRITICAL RELEVANCE STATEMENT

This prospective study shows DWI-based virtual magnetic resonance elastography and intravoxel incoherent motion-based functional parameters to quantify placenta elastography and microcirculation in small-for-gestational-age patients, which could complement existing non-invasive methods for monitoring and predicting neonatal perinatal adverse outcome.

KEY POINTS

• vMRE is an emerging non-invasive imaging technique for evaluating placenta stiffness. • SGA infants with adverse outcome have stiffer placental elasticity and lower microcirculation. • Risk factors combination displayed better efficacy in predicting adverse outcomes of SGA.

Imaging of Acute Abdominopelvic Pain in Pregnancy and Puerperium-Part I: Obstetric (Non-Fetal) Complications

Acute abdominopelvic pain in pregnant and postpartum patients presents clinical and therapeutic challenges, often requiring quick and accurate imaging diagnosis. Ultrasound remains the primary imaging investigation. Magnetic resonance imaging (MRI) has been shown to be a powerful diagnostic tool in the setting of acute abdominal pain during pregnancy and puerperium. MRI overcomes some drawbacks of US, avoiding the ionizing radiation exposure of a computed tomography (CT) scan. Although CT is not usually appropriate in pregnant patients, it is crucial in the emergency evaluation of postpartum complications. The aim of this article is to provide radiologists with a thorough familiarity with the common and uncommon pregnancy and puerperium abdominal emergencies by illustrating their imaging appearances. The present first section will review and discuss the imaging findings for acute abdominopelvic pain of obstetric (non-fetal) etiology.

Current practice of placental cord insertion documentation in Australia - A sonographer survey

Introduction

During pregnancy, the umbilical cord attaches to the placenta in a central, eccentric, marginal or velamentous location. Maternal and fetal complications are associated with marginal and velamentous cord insertions, the most clinically significant being perinatal mortality due to undiagnosed vasa praevia. Current literature describes a wide variation regarding regulation of placental cord insertion (PCI) documentation during antenatal ultrasound examinations. This prospective cross-sectional study aimed to assess the current practice of antenatal PCI documentation in Australia.

Methods

Members of the Australian Sonographer Accreditation Registry were invited to participate in an online survey which was distributed between February and March 2022.

Results

Four hundred ninety sonographers met the inclusion criteria for the study of which 330 (67.3%) have more than 10 years' experience as a sonographer and 375 (76.5%) are employed primarily in a public or private setting offering general ultrasound. Most respondents (89.6%) indicated documentation of the PCI site is departmental protocol at the second trimester anatomy scan (17-22 weeks gestation), but PCI documentation is protocol in less than 50% of other obstetric ultrasound examinations listed in the survey. The PCI site is included in the formal ultrasound report at a rate significantly less than inclusion in the departmental protocol and the sonographer's worksheet.

Conclusions

Considering the potential maternal and fetal complications associated with abnormal PCI and the ease at which the PCI site is identified in the first and second trimesters, we believe that standard inclusion of the PCI site in departmental protocol and in the formal ultrasound report from 11 weeks gestation, regardless of whether it is normal or abnormal, would prove invaluable.

Nanomedicines for Improved Management of Ectopic Pregnancy: A Narrative Review

Ectopic pregnancy (EP) - the implantation of an embryo outside of the endometrial cavity, often in the fallopian tube - is a significant contributor to maternal morbidity and leading cause of maternal death due to hemorrhage in first trimester. Current diagnostic modalities including human chorionic gonadotropin (hCG) quantification and ultrasonography are effective, but may still misdiagnose EP at initial examination in many cases. Depending on the patient's hemodynamic stability and gestational duration of the pregnancy, as assessed by history, hCG measurement and ultrasonography, management strategies may include expectant management, chemotherapeutic treatment using methotrexate (MTX), or surgical intervention. While these strategies are largely successful, expectant management may result in tubal rupture if the pregnancy does not resolve spontaneously; MTX administration is not always successful and may induce significant side effects; and surgical intervention may result in loss of the already-damaged fallopian tube, further hampering the patient's subsequent attempts to conceive. Nanomaterial-based technologies offer the potential to enhance delivery of diagnostic imaging contrast and therapeutic agents to more effectively and safely manage EP. The purpose of this narrative review is to summarize the current state of nanomedicine technology dedicated to its potential to improve both the diagnosis and treatment of EP.

Maternal hypothyroidism and its effect on placental histopathology in singleton live births resulting from in vitro fertilization treatment

We aimed to examine the impact of maternal hypothyroidism on placental pathology and perinatal outcomes in singleton live births resulting from IVF, using medical records of IVF births between 2009 and 2017 at a tertiary hospital. The primary outcomes included anatomical, inflammation, vascular malperfusion, and villous maturation placental features. Secondary outcomes included foetal, maternal, perinatal, and delivery complications. There were 1,057 live births, of which 103 (9.7%) and 954 (90.3%) were in the study and control groups, respectively. Patients in the study group were more likely to have diabetes mellitus, polycystic ovarian syndrome, gestational diabetes mellitus, and non-reassuring foetal heart rate (NRFHR) tracing during delivery. After adjustment for potential confounding factors, hypothyroidism was significantly associated with the bilobed placenta (aOR 4.1; 95% CI 1.2-14.3), retroplacental haematoma (aOR 2.4; 95% CI 1.2-4.9), decidual arteriopathy (aOR 2.0; 95% CI 1.2-4.1) and subchorionic thrombi (aOR 2.4; 95% CI 1.3-5.0). Additionally, there was a statistically significant relationship with NRFHR tracing. The incidence of acute chorioamnionitis and severe foetal inflammatory response was higher in the study group. In conclusion, the placental histopathology patterns of singleton IVF live births show that maternal hypothyroidism has a significant impact on adverse perinatal outcomes.

The role of the radiologist in diagnosing placenta percreta: a case report and review of the literature

Placenta percreta is the most severe and least common form of placental insertion abnormalities. The increasing frequency of C-Section deliveries has led to more of these abnormalities. Ultrasound and magnetic resonance imaging (MRI) have a key role in diagnosing these abnormal adherences since it shows best transmural extension of the placental tissue. We report a case of a woman with a previous cesarean delivery who had been diagnosed with a placenta preavia on ultrasound and a suspicion of transmural extension with her MRI later showing a placenta percreta.

Normal placental structural anatomy: ultrasound and doppler features elucidated with US-MR image fusion and ferumoxytol-enhanced MRI

PURPOSE

To elucidate ultrasound features of normal placental anatomy through correlation of gray-scale and ultrasound Doppler with ferumoxytol-enhanced MRI features using US-MR image fusion.

METHODS

All patients referred to MR for ultrasound findings worrisome for PAS (placenta accreta spectrum) were included in this retrospective study. MR studies included a ferumoxytol-enhanced T1-weighted MRI. Ultrasound imaging included gray-scale, color Doppler, power Doppler, and spectral Doppler techniques. After the MR, US-MRI fusion was performed by co-registering a MR acquisition to real-time US, which allowed precise, point-to-point correlation of placental features.

RESULTS

Fourteen patients at risk for PAS were studied using the US-MR image fusion. At delivery, there were six cases without PAS (gestational age range: 24 weeks 3 days to 34 weeks 0 days), and these composed the study cohort. Placental features that were on high signal intensity on post-ferumoxytol acquisitions represent spaces with maternal blood flow and corresponded to hypoechoic areas on ultrasound created by a paucity of reflective interfaces (villi). Color and spectral Doppler allowed the separation of maternal and fetal circulations in individual perfusional domains and demonstrated spiral artery inflow, circulation around the villous tree, and return of blood flow to the basal plate. Recognizable histopathologic features by ultrasound included the central cavity, villous tree, and venous return channels.

CONCLUSION

Internal placental architecture can be discerned on ultrasound. This anatomy can be correlated and confirmed with ferumoxytol-MR through US-MR fusion. Understanding this structural anatomy on ultrasound could serve as a basis to identify normal and abnormal placental features.

Texture analysis of sonographic image of placenta in pregnancies with normal and adverse outcomes, a pilot study

INTRODUCTION

Many maternal and fetal morbidity and mortality from complications of pregnancy have been attributed to placenta abnormality. Placenta assessment in developing countries is mainly through ultrasonography which is subjective and prone to error. Objective assessment of placental abnormalities through texture analysis has been frequently done using magnetic resonance images with little done on ultrasound generated images, thus, the need for this study. The study is aimed at using statistical texture analysis in characterizing placenta tissue into normal and abnormal placenta as well as testing the accuracy of different texture analysis algorithms in differentiating placenta into normal and abnormal placental tissues.

METHODS

This longitudinal study involved 500 ultrasound-generated placenta images from patients screened for adverse pregnancy outcomes in a private hospital in Enugu. These images were loaded onto an HP laptop for viewing. Two regions of interest were selected from the placenta tissue where texture features were extracted and were classified into normal and abnormal placentas using MaZda® software version 47 while the accuracy of the classification descriptors was assessed using WEKA classification algorithms.

RESULTS

Co-occurrence matrix, run length matrix and histogram parameters differentiated normal placenta tissue from abnormal placental tissues (p-value <0.05) while variance is the only absolute gradient parameter that can differentiate normal placenta tissue from abnormal placenta tissues. All feature descriptors show high classification accuracy using KNN and ANN algorithms.

CONCLUSION

Texture analysis can differentiate normal placenta tissues from abnormal placenta tissue which will reduce the errors associated with subjective assessment of the placenta echogenicity.

IMPLICATIONS FOR PRACTICE

Integrating these computer-aided algorithms into our ultrasound machines will lead to early detection of abnormal placenta tissues as early management results in better pregnancy outcomes.

Feto-placental Unit: From Development to Function

The placenta is an intriguing organ that allows us to survive intrauterine life. This essential organ connects both mother and fetus and plays a crucial role in maternal and fetal well-being. This chapter presents an overview of the morphological and functional aspects of human placental development. First, we describe early human placental development and the characterization of the cell types found in the human placenta. Second, the human placenta from the second trimester to the term of gestation is reviewed, focusing on the morphology and specific pathologies that affect the placenta. Finally, we focus on the placenta's primary functions, such as oxygen and nutrient transport, and their importance for placental development.

Fetal MRI prior to intrauterine surgery of open neural tube defects: What does the radiologist need to know

The management of myelomeningocele study trial showed significant prognostic improvement in fetal repair before 26 weeks of gestation. Hence, surgery in utero represents the best treatment option for open-neural tube defects (NTDs). Fetal surgery of open-NTDs has specific inclusion and exclusion criteria, which can be adequately studied with fetal MRI. The main concern: the spine (spinal defects other than Myelomeningocele and Myeloschisis, the level of the lesion higher than T1 or lower than S1 and the degree of kyphosis ≥ 30°), the skull/brain (no cerebellum herniation and Chiari II malformation and the presence of any intracranial abnormality unrelated to open NTDs), the uterus (cervix length less than 2 cm, multiple gestations and placental and uterine abnormalities) and any other fetal abnormality not attributed to spinal defect. In this review, we describe the fundamental role of fetal MRI in supporting therapeutic decisions in pre-surgery intrauterine planning through the accurate and comprehensive description of findings, providing a proposal of a structured report. In addition, we describe how post-surgical MRI is important in investigating the effectiveness of surgery and detecting repairing complications.

Ferumoxytol-enhanced magnetic resonance imaging with volume rendering: A new approach for the depiction of internal placental structure in vivo

INTRODUCTION

Placental function is vitally important, but placental assessment is limited by current imaging methods in vivo. The goal of this study is to determine if ferumoxytol-enhanced MR studies might be used to depict placental structure during pregnancy.

METHODS

Ten pregnant women were referred for MRI evaluation of abnormal placentation. The study group was composed five of these patients whose placentas were normal at pathology. MR studies consisted of pre-contrast SSFSE (single-shot fast spin-echo), SSFP (steady-state free procession), diffusion, and ferumoxytol-enhanced acquisitions. The post-contrast sequences were compared to pre-contrast SSFSE, SSFP, and diffusion acquisitions for features of correspondence. MR images were also compared to histopathology for anatomic landmarks including the three-ring pattern of the functional vascular exchange unit (the placentone) created by this central cavity surrounded by a ring of clustered villi, and an outer ring of dispersed villi corresponding to the maternal venous outflow channel. The measured sizes of these features on MR were compared to reported sizes.

RESULTS

Post-ferumoxytol images showed enhancement of the maternal blood within the placenta, notably the intervillous space and the myometrial vessels. The unenhanced fetal vessels were most visible on the MinIP (minimum intensity projection) images; the enhanced maternal vessels were most visible on the MIP (maximum intensity projection) images. Composite MIP/MinIP images show the relation of maternal and fetal circulations. The signal intensities replicate the relative contributions from enhanced maternal blood and unenhanced chorionic villi.

DISCUSSION

Ferumoxytol-enhanced MR imaging can depict the internal anatomy of the placenta in vivo of clarity and detail. This could represent a new diagnostic approach to placental disorders.

Pathology of the Placenta in Singletons after Assisted Reproductive Technology Compared to Singletons after Spontaneous Conception: A Systematic Review

Background: We reviewed the literature comparing the pathological characteristics of singleton births conceived after assisted reproductive technology (ART) with those after spontaneous conception. Methods: We reviewed PubMed, EMBASE, Ovid MEDLINE, Google Scopus, Scholar, Cochrane Central Register of Controlled Trials and the Web of Science for the previous 10 years, up to November 2022. Results: Four eligible studies included 3445 placentas, 806 after ART (IVF/ICSI). Placentas after ART differed in frequency of retroplacental and marginal hematomas (p = 0.04), increased thickness (p = 0.02), higher overall occurrences of vascular and anatomical pathology (p < 0.001) and more frequent marginal (p = 0.001) and membranous (p = 0.02) umbilical cord insertion than placentas from non-ART pregnancies. Conclusion: Further research is needed to determine the extent to which these placental changes in ART pregnancies alter its function and pregnancy outcome.

Ferumoxytol dynamic contrast enhanced magnetic resonance imaging identifies altered placental cotyledon perfusion in rhesus macaques†

Identification of placental dysfunction in early pregnancy with noninvasive imaging could be a valuable tool for assessing maternal and fetal risk. Dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) can be a powerful tool for interrogating placenta health. After inoculation with Zika virus or sham inoculation at gestation age (GA) 45 or 55 days, animals were imaged up to three times at GA65, GA100, and GA145. DCE MRI images were acquired at all imaging sessions using ferumoxytol, an iron nanoparticle-based contrast agent, and analyzed for placental intervillous blood flow, number of perfusion domains, and perfusion domain volume. Cesarean section was performed at GA155, and the placenta was photographed and dissected for histopathology. Photographs were used to align cotyledons with estimated perfusion domains from MRI, allowing comparison of estimated cotyledon volume to pathology. Monkeys were separated into high and low pathology groups based on the average number of pathologies present in the placenta. Perfusion domain flow, volume, and number increased through gestation, and total blood flow increased with gestation for both low pathology and high pathology groups. A statistically significant decrease in perfusion domain volume associated with pathology was detected at all gestational ages. Individual perfusion domain flow comparisons demonstrated a statistically significant decrease with pathology at GA100 and GA145, but not GA65. Since ferumoxytol is currently used to treat anemia during human pregnancy and as an off-label MRI contrast agent, future transition of this work to human pregnancy may be possible.

Unfolding the role of placental-derived Extracellular Vesicles in Pregnancy: From homeostasis to pathophysiology

The human placenta is a critical structure with multiple roles in pregnancy, including fetal nutrition and support, immunological, mechanical and chemical barrier as well as an endocrine activity. Besides, a growing body of evidence highlight the relevance of this organ on the maternofetal wellbeing not only during gestation, but also from birth onwards. Extracellular vesicles (EVs) are complex macromolecular structures of different size and content, acting as carriers of a diverse set of molecules and information from donor to recipient cells. Since its early development, the production and function of placental-derived EVs are essential to ensure an adequate progress of pregnancy. In turn, the fetus receives and produce their own EVs, highlighting the importance of these components in the maternofetal communication. Moreover, several studies have shown the clinical relevance of EVs in different obstetric pathologies such as preeclampsia, infectious diseases or gestational diabetes, among others, suggesting that they could be used as pathophysiological biomarkers of these diseases. Overall, the aim of this article is to present an updated review of the published basic and translational knowledge focusing on the role of placental-derived EVs in normal and pathological pregnancies. We suggest as well future lines of research to take in this novel and promising field.

Placenta segmentation in ultrasound imaging: Addressing sources of uncertainty and limited field-of-view

Automatic segmentation of the placenta in fetal ultrasound (US) is challenging due to the (i) high diversity of placenta appearance, (ii) the restricted quality in US resulting in highly variable reference annotations, and (iii) the limited field-of-view of US prohibiting whole placenta assessment at late gestation. In this work, we address these three challenges with a multi-task learning approach that combines the classification of placental location (e.g., anterior, posterior) and semantic placenta segmentation in a single convolutional neural network. Through the classification task the model can learn from larger and more diverse datasets while improving the accuracy of the segmentation task in particular in limited training set conditions. With this approach we investigate the variability in annotations from multiple raters and show that our automatic segmentations (Dice of 0.86 for anterior and 0.83 for posterior placentas) achieve human-level performance as compared to intra- and inter-observer variability. Lastly, our approach can deliver whole placenta segmentation using a multi-view US acquisition pipeline consisting of three stages: multi-probe image acquisition, image fusion and image segmentation. This results in high quality segmentation of larger structures such as the placenta in US with reduced image artifacts which are beyond the field-of-view of single probes.

Accuracy of Magnetic Resonance Imaging in Diagnosing Placenta Accreta: A Systematic Review and Meta-Analysis

Background

The disease burden and incidence of placenta accreta are increasing worldwide. The morbidity and mortality associated with undiagnosed placenta accreta are both high, highlighting the important of early diagnosis and intervention. In recent years, increasing studies are exploring the diagnostic value of magnetic resonance imaging (MRI) for placenta accreta. Compared with traditional ultrasound, MRI has the advantages of high-resolution, multiangle imaging, and less influence by amniotic fluid and intestinal gas. However, the reported diagnostic accuracy among studies was inconsistent. Therefore, this study is aimed at exploring the diagnostic value of MRI for placenta accreta by systematic review and meta-analysis.

Methods

Relevant literature were systematically searched in PubMed, Ovid, Embase, ScienceDirect database, CNKI, and Wanfang database by using medical subject headings and relevant diagnostic terminologies such as sensitivity, specificity, likelihood ratio, receiver-operating characteristic curve, and area under the curve. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and area under the curve of the included literature were analyzed using stata 17.0 software. Publication bias of the included studies was assessed by Deek's funnel plot. Cochrane Q statistics and I² statistics were used to test the heterogeneity.

Results

A total of 10 primary publications, comprising 4 retrospective studies and 6 prospective studies, were included in this meta-analysis. The gestational weeks of pregnant women ranged from 32 to 35 weeks, and the sample size ranged from 37 cases to 575 cases. Only 4 studies used the blind method in the process of clinical diagnosis by MRI. The combined sensitivity, specificity, and area of curve under summary receiver-operating characteristic for the diagnosis of placenta accreta by MRI were 0.88 (95% CI, 0.79-0.93), 0.79 (95% CI, 0.68-0.87), and 0.91 (95% CI, 0.88.-0.93), respectively. The combined positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and diagnostic score were 4.17 (95% CI, 2.62-6.66), 0.16 (95% CI, 0.09-0.29), 26.61 (95% CI, 10.22-69.28), and 3.28 (95% CI, 2.32-4.24), respectively. No publication bias was noted.

Conclusion

Diagnosis of placenta accreta by MRI has good accuracy and predictive value that warrants clinical promotion.

Magnetic resonance imaging (MRI) of normal human placentae

INTRODUCTION

The MRI appearances of the human placenta in the absence of maternal or fetal pathology have not been extensively studied, with only a few studies reporting findings in the uncomplicated pregnancy. The purpose of this study is to review the placental MRI appearances in low-risk pregnancies in a prospective study.

METHODS

A prospective observational study of placental MRI in low-risk pregnancies was initially planned, however recruitment was terminated early due to the COVID19 pandemic. The protocol was subsequently modified to compare the placental appearances in the enrolled cohort with pregnancies having had MRI for non-placental pathologies. The data from the two groups were then pooled to assess the range of normal placental appearances.

RESULTS

Eighty-three pregnancies were prospectively assessed with MRI at a median gestation of 29 weeks (range 14-39) from a mixed group of prospective cases (n = 28) and retrospectively recruited obstetric MRI (n = 55). Placental thickness in the third trimester ranged from 18 to 35 mm. T2 heterogeneity was seen in 75% (25/33) at second trimester and by the third trimester 50% (25/50) were moderately or markedly heterogenous. T2 dark bands (>6 mm) were seen in 9% (3/33) and 20% (10/50) of second and third trimester pregnancies, respectively. Undetectable myometrium or loss of the subplacental myometrial plane was present in 15% (5/33) of second and 38% (19/50) of third trimester placentae.

CONCLUSION

This qualitative study of normal placental MRI appearances expands the current knowledge base by confirming they vary, evolve with gestation, and can overlap with signs of placenta accreta spectrum.

Achados na ressonância magnética do espectro do acretismo placentário: ensaio iconográfico

Resumo Acretismo placentário é uma condição caracterizada pela implantação anormal da placenta, que pode ser subdividida em três espectros de acordo com o seu grau de invasão: placenta acreta (ultrapassa a decídua basal e adere ao miométrio), placenta increta (penetra o miométrio) e placenta percreta (invasão da serosa uterina ou de tecidos/órgãos adjacentes). A incidência de acretismo placentário aumentou significativamente nas últimas décadas, principalmente em função da elevação das taxas de cesarianas, sendo este o seu principal fator de risco. A sua identificação pré-natal precisa permite um tratamento ideal com equipe multidisciplinar, minimizando significativamente a morbimortalidade materna. Os exames de escolha são a ultrassonografia e a ressonância magnética (RM), sendo a RM um método complementar indicado quando a avaliação ultrassonográfica é duvidosa, para pacientes com fatores de risco para acretismo placentário ou quando a placenta tem localização posterior. A RM é preferível também para avaliar invasão de órgãos adjacentes, oferecendo um campo de visão mais amplo, o que melhora o planejamento cirúrgico. Diversas características na RM são descritas no acretismo placentário, incluindo bandas hipointensas em T2 intraplacentárias, protuberância uterina anormal e heterogeneidade placentária. O conhecimento desses achados e a combinação de mais de um critério aumentam a confiabilidade do diagnóstico.

The Pivotal Role of the Placenta in Normal and Pathological Pregnancies: A Focus on Preeclampsia, Fetal Growth Restriction, and Maternal Chronic Venous Disease

The placenta is a central structure in pregnancy and has pleiotropic functions. This organ grows incredibly rapidly during this period, acting as a mastermind behind different fetal and maternal processes. The relevance of the placenta extends far beyond the pregnancy, being crucial for fetal programming before birth. Having integrative knowledge of this maternofetal structure helps significantly in understanding the development of pregnancy either in a proper or pathophysiological context. Thus, the aim of this review is to summarize the main features of the placenta, with a special focus on its early development, cytoarchitecture, immunology, and functions in non-pathological conditions. In contraposition, the role of the placenta is examined in preeclampsia, a worrisome hypertensive disorder of pregnancy, in order to describe the pathophysiological implications of the placenta in this disease. Likewise, dysfunction of the placenta in fetal growth restriction, a major consequence of preeclampsia, is also discussed, emphasizing the potential clinical strategies derived. Finally, the emerging role of the placenta in maternal chronic venous disease either as a causative agent or as a consequence of the disease is equally treated.

Imaging Review of Obstetric Sequelae of Maternal Diabetes Mellitus

Diabetes mellitus, whether preexisting or gestational, poses significant risk to both the mother and the developing fetus. A myriad of potential fetal complications in the setting of diabetic pregnancies include, among others, congenital anomalies, delayed fetal lung maturity, macrosomia, and increased perinatal morbidity and mortality. Congenital anomalies most commonly involve the nervous, cardiovascular, genitourinary, and musculoskeletal systems. Delayed fetal lung maturity, probably secondary to hyperglycemia suppressing surfactant secretion, is a major determinant of perinatal morbidity and mortality. Besides the potential complications encountered during cesarean delivery in macrosomic fetuses, vaginal delivery is also associated with increased risks of shoulder dystocia, clavicular and humeral fractures, and brachial plexus palsy. Maternal complications are related to the increased risk of hypertensive diseases of pregnancy and associated preeclampsia and hemolysis, elevated liver function, and low platelets (HELLP) syndrome, as well as complications encountered at the time of delivery secondary to fetal macrosomia and cesarean delivery. Additional conditions encountered in the setting of maternal diabetes include polyhydramnios, placental thickening, and two-vessel umbilical cord, each of which is associated with adverse fetal and maternal outcomes including fetal growth restriction, preterm labor, placental abruption, and premature rupture of membranes. Imaging plays a vital role in the evaluation of the mother and the fetus and can provide invaluable information that can be used by maternal fetal medicine to manage this patient population effectively. The authors review the pathophysiologic alterations induced by diabetes in pregnancy, discuss the imaging spectrum of diabetic embryopathy, and provide a detailed review of potential associated maternal complications. Online supplemental material is available for this article. ^©RSNA, 2021.

Emerging placental biomarkers of health and disease through advanced magnetic resonance imaging (MRI)

Placental dysfunction is a major cause of fetal demise, fetal growth restriction, and preterm birth, as well as significant maternal morbidity and mortality. Infant survivors of placental dysfunction are at elevatedrisk for lifelong neuropsychiatric morbidity. However, despite the significant consequences of placental disease, there are no clinical tools to directly and non-invasively assess and measure placental function in pregnancy. In this work, we will review advanced MRI techniques applied to the study of the in vivo human placenta in order to better detail placental structure, architecture, and function. We will discuss the potential of these measures to serve as optimal biomarkers of placental dysfunction and review the evidence of these tools in the discrimination of health and disease in pregnancy. Efforts to advance our understanding of in vivo placental development are necessary if we are to optimize healthy pregnancy outcomes and prevent brain injury in successive generations. Current management of many high-risk pregnancies cannot address placental maldevelopment or injury, given the standard tools available to clinicians. Once accurate biomarkers of placental development and function are constructed, the subsequent steps will be to introduce maternal and fetal therapeutics targeting at optimizing placental function. Applying these biomarkers in future studies will allow for real-time assessments of safety and efficacy of novel interventions aimed at improving maternal-fetal well-being.

Pictorial review of the postmortem computed tomography in neonaticide cases

Neonaticide is defined by the deliberate killing or homicide of a child within 24 h of its birth. In this context, three fundamental questions are generally asked of the forensic pathologist: what is the cause of death of the neonate? Was the child viable (i.e., what is the gestational age of the neonate)? Finally, was the neonate stillborn or liveborn?Postmortem imaging can help answer these questions by conducting (1) a complete lesional analysis of the body and the placenta, (2) an estimation of the gestational age by measuring the lengths of the diaphyseal long bones, and (3) an analysis of the aeration of the lungs and intestines. Using the details of 18 cases, we illustrate aspects of neonaticide cases in postmortem computed tomography (PMCT), offering detailed examples of notable postmortem changes and abnormalities, especially in the analysis of the pulmonary parenchyma. This article presents a useful iconography for the radiologist confronted with this rare yet complex forensic situation.

Normative placental structure in pregnancy using quantitative Magnetic Resonance Imaging

INTRODUCTION

To characterize normative morphometric, textural and microstructural placental development by applying advanced and quantitative magnetic resonance imaging (qMRI) techniques to the in-vivo placenta.

METHODS

We enrolled 195 women with uncomplicated, healthy singleton pregnancies in a prospective observational study. Women underwent MRI between 16- and 40-weeks' gestation. Morphometric and textural metrics of placental growth were calculated from T2-weighted (T2W) images, while measures of microstructural development were calculated from diffusion-weighted images (DWI). Normative tables and reference curves were constructed for each measured index across gestation and according to fetal sex.

RESULTS

Data from 269 MRI studies from 169 pregnant women were included in the analyses. During the study period, placentas undergo significant increases in morphometric measures of volume, thickness, and elongation. Placental texture reveals increasing variability with advancing gestation as measured by grey level non uniformity, run length non uniformity and long run high grey level emphasis. Placental microstructure did not vary with gestational age. Placental elongation was the only metric that differed significantly between male and female fetuses.

DISCUSSION

We report quantitative metrics of placental morphometry, texture and microstructure in a large cohort of healthy controls during the second and third trimesters of pregnancy. These measures can serve as normative references of in-vivo placental development to better understand placental function in high-risk conditions and allow for the early detection of placental mal-development.

The comparative aspects of hystricomorph subplacenta: potential endocrine organ

Background

The placenta of hystricomorph rodents, lagomorphs and some primates includes an unusual structure, termed a subplacenta, which essentially consists of trophoblastic cells located deep to the central implantation site within the area of decidualization. It has been suggested that the subplacenta is functionally important, although considerable controversy remains on the issue. In this context, our objective was to compare the architecture and structure of the subplacentas of different hystricomorph species, to investigate the possibility that it is active in hormone synthesis.

Methods

In total, the placentas of 3 capybaras (Hydrochaeris hydrochaeris), 2 pacas (Agouti paca), 5 agoutis (Dasyprocta leporina), 5 rock cavies (Kerodon rupestris) and 3 guinea pigs (Cavia porcellus) at different stages of pregnancy (early, middle and near term) were used for gross and microscopic examination. This included the preparation of latex injection casts, immunohistochemistry for steroidogenic enzymes, scanning and transmission electron microscopy. Tissue steroid concentrations were also determined.

Results

The gross morphology and microvascular arrangement of the subplacentas were similar among the hystricomorphs studied including ultra-structural verification of cytotrophoblast and syncytiotrophoblast in all species. In guinea pigs, trophoblast cells exhibited characteristics consistent with intense metabolic and secretory activity in general. However, immuno-histochemical evidence also indicated that subplacental trophoblast expressed key steroidogenic enzymes, mainly in the chorionic villus region, consistent with tissue steroid concentrations.

Conclusions

The subplacentas within placentas of hystricomorph rodent species are structurally similar and, in guinea pigs, have potential for steroid hormone secretion from, at least the early stages of pregnancy.

Ultrasound evaluation of the placenta in healthy and placental syndrome pregnancies: A systematic review

INTRODUCTION

An antepartum screening method to determine normal and abnormal placental function is desirable in the prevention of maternal and fetal pregnancy complications. Placental appearance can easily be obtained and evaluated using 2D ultrasonography, but surprisingly little is known about the change in placental appearance during gestation. Aim of this systematic review was to describe the antepartum placental appearance in placenta syndrome (PS) pregnancies, and to compare this to the appearance in healthy pregnancies.

METHODS

A systematic review investigating placental thickness, -lakes and/or -calcifications by ultrasound examination in both uncomplicated (reference group) and PS pregnancies in relation to gestational age was performed. English literature was searched using PubMed (NCBI), EMBASE (Ovid) and the Cochrane Library, from database inception until September 2020. Data on placental thickness was presented as a continuous variable or as the proportion of abnormal placental thickness. Data on placental lakes and -calcifications was presented as prevalence (%). There was no restriction applied on the definition of placental lakes or -calcifications. Due to heterogeneity, pooling of the results was not performed.

RESULTS

A total of 28 studies were included describing 1719 PS cases; consisting of 370 (21 %) cases with preeclampsia or pregnancy induced hypertension, 1341 (78 %) cases with fetal growth restriction (FGR) or small for gestational age (SGA), and 8 (1%) cases with combined clinical expressions. In addition, the reference group comprised 3315 pregnant women. Placental thickness showed an increase between the first and second trimester, which was higher in PS- compared to uncomplicated pregnancies. Placental lakes were frequently observed in FGR and SGA pregnancies, especially in the second trimester. Grade 3 calcifications were most prominent in the PS pregnancies, specifically in the late second and third trimester. Moreover, in the reference group, no grade 3 calcifications were reported before 35 weeks of gestation.

CONCLUSION

Placental appearance in PS-pregnancies shows higher placental thickness and greater presence of placental lakes and -calcifications compared to uncomplicated pregnancies. Standardized definitions of (ab-)normal placental appearance and longitudinal research in both healthy and complicated pregnancies are needed to improve personalized obstetric care.

Placental magnetic resonance imaging: normal appearance, anatomical variations, and pathological findings

Placental magnetic resonance imaging (MRI) has been increasingly requested, especially for the evaluation of suspected cases of placental adhesive disorders, generally known as placenta accreta. Abdominal radiologists need to become familiar with normal placental anatomy, anatomical variations, the current terminology, and major placental diseases that, although rare, are important causes of maternal and fetal morbidity and mortality. The aim of this didactic pictorial essay is to illustrate various findings on placental MRI, as well as to emphasize the importance of communication between radiologists and obstetricians in the search for best practices in the management of the affected patients.

Intra-System Reliability Assessment of 2-Dimensional Shear Wave Elastography

The availability of 2-Dimensional Shear Wave Elastography (2D-SWE) technology on modern medical ultrasound systems is becoming increasingly common. The technology is now being used to investigate a range of soft tissues and related pathological conditions. This work investigated the reliability of a single commercial 2D-SWE system using a tissue-mimicking elastography phantom to understand the major causes of intra-system variability. Sources of shear wave velocity (SWV) measurement variability relates to imaging depth, target stiffness, sampling technique and the operator. Higher SWV measurement variability was evident with increasing depth and stiffness of the phantom targets. The influence of the operator was minimal, and variations in sampling technique had little impact on the SWV.

Sonographic Detection of Placenta Percreta With Associated Placenta Previa and Succenturiate Lobe

Placenta percreta is the most complicated degree of the placenta accreta spectrum (PAS). It involves placental invasion through the uterine myometrium and into, or beyond, the uterine serosa, which can ultimately lead to severe maternal hemorrhage. Placenta previa is often associated with PAS and can be a significant indicator, along with other clinical factors. Sonography has historically been a highly accurate and safe imaging modality to assess the PAS. This specific case examines a patient with a pathologically proven percreta with an associated previa and succenturiate placental lobe.

Review of MRI imaging for placenta accreta spectrum: Pathophysiologic insights, imaging signs, and recent developments

Placenta Accreta Spectrum (PAS) refers to the range of abnormally adhesive and penetrative placental tissue at a uterine scar. PAS is divided into accreta, increta, and percreta based on degree of myometrial invasion. Its incidence has increased, and PAS is now the leading indication for emergency peripartum hysterectomy in the setting of catastrophic hemorrhage from a non-separating placenta. The recent release of the International Federation of Gynecology and Obstetrics (FIGO) guidelines in 2018 coupled with the joint consensus statement from the Society of Abdominal Radiology (SAR) and European Society of Urogenital Radiology (ESUR) in 2020 reflect decades worth of diagnostic and therapeutic advances in this field. Although the increasing role of MRI in PAS diagnosis is evident, the literature on PAS reveals several disparate but conceptually overlapping MRI signs. Identifying and differentiating between placenta increta and percreta on imaging may be quite challenging even with MRI and sometimes even on final pathology. In this review, we aim to (i) provide a clarified understanding of PAS pathophysiology, (ii) comprehensively review and classify MRI signs based on pathophysiologic underpinnings, (iii) highlight shortcomings in the current PAS literature; and (iv) highlight best practice guidelines for imaging diagnosis of PAS.

Impact of intramural non-cavity-distorting leiomyoma on placental histopathology and perinatal outcome in singleton live births resulting from in vitro fertilization treatment

PURPOSE

To evaluate the effect of non-cavity-distorting intramural leiomyomas on the placental histopathology pattern and perinatal outcome in singleton live births resulting from in vitro fertilization treatment.

METHODS

The study population included all singleton live births following in vitro fertilization treatment with autologous oocytes during the period from 2009 to 2017. Primary outcomes included anatomical, inflammation, vascular malperfusion, and villous maturation placental features. Secondary outcomes included fetal, maternal, delivery, and perinatal complications.

RESULTS

A total of 1119 live births were included in the final analysis and were allocated to the group of pregnancies with non-cavity-distorting intramural myomas (n = 101) and without myomas (n = 1018). After the adjustment for confounding factors, the non-cavity-distorting intramural myomas were found to be significantly associated with assisted placental delivery (OR 2.4; 95% CI 1.5-3.9), furcate cord insertion (OR 3.6; 95% CI 1.4-9.3), circumvallate membranes insertion (OR 5.2; 95% CI 1.4-19.3), chronic deciduitis (OR 8.2; 95% CI 1.6-42.2), focal intramural fibrin deposition (OR 25.1; 95% CI 2.1-306.2), subchorionic thrombi (OR 3.6; 95% CI 1.7-7.6), maternal vasculopathy (OR 2.5; 95% CI 1.2-5.5), and chorangioma (OR 5.9; 95% CI 1.4-25.2) as well as with the failure of labor progress (OR 2.4; 95% CI 1.3-4.4) and induction (OR 3.2; 95% CI 1.2-9.0).

CONCLUSION

Intramural non-cavity-distorting myomas have a significant impact on the placental histopathology with a higher incidence of dysfunctional labor.

Magnetic resonance imaging of the female pelvis after Cesarean section: a pictorial review

The rate of Cesarean sections (C-sections) in Poland increased from 21.7% in 2001 to 43.85% in 2017 even though the Polish Society of Gynecologists and Obstetricians highlights the negative consequences of C-section for both mother and child and recommends to make every possible effort to reduce its percentage, following the World Health Organization recommendations. There is a long list of possible complications related to the uterine scar after C-section, including uterine scar dehiscence, uterine rupture, abdominal and pelvic adhesions, uterine synechiae, ectopic pregnancy, anomalous location of the placenta, placental invasion, and—rarely—vesicouterine or uterocutaneous fistulas. Ultrasound (US) remains the first-line modality; however, its strong operator- and equipment dependence and other limitations require further investigations in some cases. Magnetic resonance imaging (MRI) is the second-line tool which is supposed to confirm, correct, or complete the sonographic diagnosis thanks to its higher tissue resolution and bigger field of view. This article will discuss the spectrum of C-section complications in the MR image-rich form and will provide a systematic discussion of the possible pathology that can occur, showing comprehensive anatomical insight into the pelvis after C-section thanks to MRI that facilitates clinical decisions.

Incidental amniocele in a case of antepartum haemorrhage

An amniocele, or contained uterine rupture, is a phenomenon in which there is herniation of the amniotic sac through a uterine defect, secondary to various causes. It is associated with severe morbidity and mortality. This case presents the findings in a 36-year-old female at 29 weeks gestation who was initially managed as antepartum haemorrhage secondary to placenta previa, based on ultrasound. Upon further imaging, an amniocele was diagnosed. This case report illustrates the importance of early identification of this life-threatening condition.

Cell-free mitochondrial DNA increases in maternal circulation during healthy pregnancy: a prospective, longitudinal study

Mitochondrial DNA (mtDNA) exposed to the extracellular space due to cell death has immunostimulatory properties. Case-control studies reported a positive association between odds of developing preeclampsia and circulating mtDNA. These findings are based on relative quantification protocols that do not allow determination of absolute concentrations of mtDNA and are highly sensitive to nuclear DNA contamination. Furthermore, circulating mtDNA concentrations in response to normal pregnancy, which is an inflammatory state characterized by continuous placental cell apoptosis, have not been established. The main objective of this study was to determine longitudinal changes in circulating mtDNA from preconception to first trimester, third trimester, and postpartum in healthy pregnant women. Absolute real-time PCR quantification of mtDNA and nuclear DNA (nDNA) was performed on whole genomic extracts from serum using TaqMan probes and chemistry. Serum cell-free mtDNA and nDNA concentrations were greater in late pregnancy as compared with early pregnancy and postpartum. Pregnant women carrying neonates at the upper quartile of birth length distribution had higher concentrations of mtDNA in late pregnancy compared with pregnancies carrying neonates at the lower quartile. The correlation between circulating mtDNA and nDNA concentrations varied by sex (i.e., pregnancies carrying female vs. male fetuses). This study is the first to establish temporal patterns of circulating cell-free mtDNA concentrations in normal human pregnancy using absolute DNA quantification techniques. Concentrations of circulating mtDNA in normal pregnancy may be used as reference values for the development of clinical prognostic or diagnostic tests in pregnant women with, or at risk of developing, gestational complications.

Improved fetal blood oxygenation and placental estimated measurements of diffusion-weighted MRI using data-driven Bayesian modeling

PURPOSE

Motion correction in placental DW-MRI is challenging due to maternal breathing motion, maternal movements, and rapid intensity changes. Parameter estimates are usually obtained using least-squares methods for voxel-wise fitting; however, they typically give noisy estimates due to low signal-to-noise ratio. We introduce a model-driven registration (MDR) technique which incorporates a placenta-specific signal model into the registration process, and we present a Bayesian approach for Diffusion-rElaxation Combined Imaging for Detailed placental Evaluation model to obtain individual and population trends in estimated parameters.

METHODS

MDR exploits the fact that a placenta signal model is available and thus we incorporate it into the registration to generate a series of target images. The proposed registration method is compared to a pre-existing method used for DCE-MRI data making use of principal components analysis. The Bayesian shrinkage prior (BSP) method has no user-defined parameters and therefore measures of parameter variation in a region of interest are determined by the data alone. The MDR method and the Bayesian approach were evaluated on 10 control 4D DW-MRI singleton placental data.

RESULTS

MDR method improves the alignment of placenta data compared to the pre-existing method. It also shows a further reduction of the residual error between the data and the fit. BSP approach showed higher precision leading to more clearly apparent spatial features in the parameter maps. Placental fetal oxygen saturation (FO₂ ) showed a negative linear correlation with gestational age.

CONCLUSIONS

The proposed pipeline provides a robust framework for registering DW-MRI data and analyzing longitudinal changes of placental function.

Incidental fetal imaging with CT: a pictorial essay

Although CT is not the first choice for abdominal imaging of pregnant patients, it can be indicated for pregnant patients with emergent life-threatening conditions. It is prudent in these cases for the radiologist to be familiar with the normal appearance of the pregnant uterus on CT and to evaluate the female pelvis for potential maternal and fetal abnormalities. We aim to provide examples of the normal CT appearance of the female pelvis related to different gestational ages and to demonstrate variant and abnormal conditions of pregnancy which may be identified by CT.

Identification of suspicious invasive placentation based on clinical MRI data using textural features and automated machine learning

OBJECTIVE

The aim of this study was to investigate whether intraplacental texture features from routine placental MRI can objectively and accurately predict invasive placentation.

MATERIAL AND METHODS

This retrospective study includes 99 pregnant women with pathologically confirmed placental invasion and 56 pregnant women with simple placenta previa. All participants underwent magnetic resonance imaging after 24 gestational weeks. The placenta was segmented in sagittal images from both turbo spin echo (TSE) and balanced turbo field echo (bTFE) sequences. Textural features were extracted from the both original and Laplacian of Gaussian (LoG)-filtered MRI images. An automated machine learning algorithm was applied to the extracted feature sets to obtain the optimal preprocessing steps, classification algorithm, and corresponding hyper-parameters.

RESULTS

A gradient boosting classifier using all textual features from original and LoG-filtered TSE images and bTFE images identified by the automated machine learning algorithm achieved the optimal performance with sensitivity, specificity, accuracy, and area under ROC curve (AUC) of 100%, 88.5%, 95.2%, and 0.98 in the prediction of placental invasion. In addition, textural features that contributed to the prediction of placental invasion differ from the features significantly affected by normal placenta maturation.

CONCLUSIONS

Quantifying intraplacental heterogeneity using LoG filtration and texture analysis highlights the different heterogeneous appearance caused by abnormal placentation relative to normal maturation. The predictive model derived from automated machine learning yielded good performance, indicating the proposed radiomic analysis pipeline can accurately predict placental invasion and facilitate clinical decision-making for pregnant women with suspicious placental invasion.

KEY POINTS

• The intraplacental texture features have high efficiency in prediction of invasive placentation after 24 gestational weeks. • The features with dominated predictive power did not overlap with the features significantly affected by gestational age.

More Than Just 2 Layers: A Comprehensive Multimodality Imaging Review of Endometrial Abnormalities

Endometrial abnormalities develop in female patients of all ages. Symptoms related to endometrial pathologies are among the most common causes of gynecologist office visits, with the radiologists playing an important role in endometrial evaluation. In some instances, the radiologist may be the first physician to note endometrial pathology. In this article, we will provide a comprehensive review of radiologic modalities utilized in the evaluation of the endometrium, as well as the imaging appearance of various endometrial disease processes.

Apparent Diffusion Coefficient of the Placenta and Fetal Organs in Intrauterine Growth Restriction

PURPOSE

This study aimed to assess apparent diffusion coefficient (ADC) of the placenta and fetal organs in intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

A prospective study of 30 consecutive pregnant women (aged 21-38 years with mean age of 31.5 years and a mean gestational week of 35 ± 2.3) with IUGR and 15 age-matched pregnant women was conducted. All patients and controls underwent diffusion-weighted magnetic resonance imaging. The ADCs of the placenta and fetal brain, kidney, and lung were calculated and correlated with neonates needing intensive care unit (ICU) admission.

RESULTS

There was a significant difference in ADC of the placenta and fetal brain, lung, and kidney (P = 0.001, 0.001, 0.04, and 0.04, respectively) between the patients and the controls. The cutoff ADCs of the placenta and fetal brain, lung, and kidney used to detect IUGR were 1.45, 1.15, 1.80, and 1.40 × 10 mm/s, respectively, with areas under the curve (AUCs) of 0.865, 0.858, 0.812, and 0.650, respectively, and accuracy values of 75%, 72.5%, 72.5%, and 70%, respectively. Combined ADC of the placenta and fetal organs used to detect IUGR revealed an AUC of 1.00 and an accuracy of 100%. There was a significant difference in ADC of the placenta and fetal brain, lung, and kidney between neonates needing admission and those not needing ICU admission (P = 0.001, 0.001, 0.002, and 0.002, respectively). The cutoff ADCs of the placenta and fetal brain, lung, and kidney used to define neonates needing ICU were 1.35, 1.25, 1.95, and 1.15 × 10 mm/s with AUCs of 0.955, 0.880, 0.884, and 0.793, respectively, and accuracy values of 86.7%, 46.7%, 76.7%, and 70%, respectively. Combined placental and fetal brain ADC used to define neonates needing ICU revealed an AUC of 0.968 and an accuracy of 93.3%.

CONCLUSION

Combined ADC of the placenta and fetal organs can detect IUGR, and combined ADC of the placenta and fetal brain can define fetuses needing ICU.

Prenatal planning of placenta previa: diagnostic accuracy of a novel MRI-based prediction model for placenta accreta spectrum (PAS) and clinical outcome

PURPOSE

To investigate the diagnostic accuracy of MRI for placenta accreta spectrum (PAS) and clinical outcome prediction in women with placenta previa, using a novel MRI-based predictive model.

METHODS

Thirty-eight placental MRI exams performed on a 1.5T scanner were retrospectively reviewed by two radiologists in consensus. The presence of T2 dark bands, myometrial thinning, abnormal vascularity, uterine bulging, placental heterogeneity, placental protrusion sign, placental recess, and percretism signs was scored using a 5-point scale. Pathology and clinical intrapartum findings were the standard of reference for PAS, while intrapartum/peripartum bleeding and emergency hysterectomy defined the clinical outcome. Receiver-operating characteristic (ROC) analysis and discriminant function analysis were performed to test the predictive power of MRI findings for both PAS and clinical outcome prediction.

RESULTS

Abnormal vascularity and percretism signs were the two most predictive MRI features of PAS. The area under the curve (AUC) of the predictive function was 0.833 (cutoff 0.39, 67% sensitivity, 100% specificity, p = 0.001). Percretism signs and myometrial thinning were the two most predictive MRI features of poor outcome. AUC of the predictive function was 0.971 (cutoff - 0.55, 100% sensitivity, 77% specificity, p < 0.001).

CONCLUSION

The diagnostic accuracy of MRI, especially considering the combination of the most predictive MRI findings, is higher when the target of the prediction is the clinical outcome rather than the PAS.

Gestational age-specific reference values of placental thickness in normal pregnant women

The aim of this study was to determine the reference values of the placental thickness in 400 normal pregnant women during weeks 16-41 of gestation who were referred to the Mahdiyeh hospital during January 2014-February 2015. The placental thickness at the junction of the umbilical artery was measured using ultrasonography. Multivariable linear regression was used to model the mean placental thickness and assess associations with measured covariates, including gestational age (GA). Centiles for placental thickness distribution were estimated according to the modulus exponential-normal model. The mean and standard deviation of the age of the participants was 31.4 ± 5.7 years. The Pearson correlation coefficient indicated a very strong positive linear correlation between GA and placental thickness (p <.001; r = 0.93). A nonlinear increase of placental thickness with estimated fetal weights was observed. GA-specific placental thicknesses for the 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, and 97.5th percentiles of placental thickness were calculated. By making use of the provided nomogram in this study, neonatal outcomes associated with the placental thickness, such as Hemoglobin Bart's disease, can be diagnosed early to improve maternal and newborn health.

Placental abruption and hemorrhage-review of imaging appearance

Placental and periplacental bleeding are common etiologies for antepartum bleeding. Placental abruption complicates approximately 1% of pregnancies and is associated with increased maternal, fetal, and neonatal morbidity and mortality. This article reviews the normal placental appearance on ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) and then discusses the different morphological appearance of placental and periplacental hematomas along with their mimics. Hematomas are classified based on the location as retroplacental, marginal subchorionic, preplacental (subamniotic), or intraplacental. Placenta-related bleeding is a common finding during first trimester ultrasound and its detection can help triage the pregnant females into low- and high-risk groups. This article reviews placenta related bleeding in the setting of trauma. Trauma can complicate pregnancy with potential severe maternal and fetal outcomes. CT is usually performed as part of the trauma workup and it can be challenging for placental evaluation. MRI can characterize the age of the hematomas and can differentiate hematomas from tumors.