In utero imaging of the placenta: importance for diseases of pregnancy

Longitudinal intravital imaging of mouse placenta

Studying placental functions is crucial for understanding pregnancy complications. However, imaging placenta is challenging due to its depth, volume, and motion distortions. In this study, we have developed an implantable placenta window in mice that enables high-resolution photoacoustic and fluorescence imaging of placental development throughout the pregnancy. The placenta window exhibits excellent transparency for light and sound. By combining the placenta window with ultrafast functional photoacoustic microscopy, we were able to investigate the placental development during the entire mouse pregnancy, providing unprecedented spatiotemporal details. Consequently, we examined the acute responses of the placenta to alcohol consumption and cardiac arrest, as well as chronic abnormalities in an inflammation model. We have also observed viral gene delivery at the single-cell level and chemical diffusion through the placenta by using fluorescence imaging. Our results demonstrate that intravital imaging through the placenta window can be a powerful tool for studying placenta functions and understanding the placental origins of adverse pregnancy outcomes.

A rare case of morbidly adherent placenta in a young Primigravida with RH negative pregnancy managed with peripartum subtotal hysterectomy

INTRODUCTION AND IMPORTANCE

Postpartum hemorrhage (PPH) can be defined as excessive bleeding (>500 ml) from the genital tract after the delivery of baby upto 6 weeks. PPH accounts for major cause of maternal mortality rate. Prevention and early intervention can prevent this complication of delivery. However condition like placenta accreta leads to retention of placenta and makes PPH inevitable.

CASE SUMMARY

We present the case of massive postpartum hemorrhage secondary to Placenta accreta in young primigravida with RH negative pregnancy. Clinical findings and investigations were not significant during her admission. She delivered the baby via vaginal route but placenta was not expelled till 30 min. Due to failed manual removal of placenta patient was shifted to OT.Manual vacuum aspiration was done in OT setting and chunks of placenta along with blood clots were obtained.Uterine balloon tamponade was inserted. Due to persistent PV bleeding subtotal hysterectomy was carried out in line for placenta accreta.

DISCUSSION

Placenta accreta being one of the life threatening obstetric condition, it should be diagnosed as early as possible and need prompt management so as to prevent maternal mortality. Due to increasing number of cesarean delivery the cases of placenta accreta has been rising but rarely in some cases can it present in young primigravida with Rh negative pregnancy.

CONCLUSION

In the cases of morbidly adherent placenta it is necessary for obstetrician to early identify such conditions and timely intervene to save the mother's life. Moreover Rh negative could be a hidden risk factor.

Small estimated placental volume (EPV) in the setting of decreased fetal movement

Although 60.5 % of clinically unexplained stillbirths can be attributed to placental insufficiency and/or fetal growth restriction, clinicians rarely calculate estimated placental volume (EPV). We present a scenario in which EPV was used to inform patient care of a 28-year-old with decreased fetal movement at 32 weeks and 1 day gestation. Although estimated fetal weight (EFW), amniotic fluid index (AFI), and nonstress test (NST) were normal, EPV was low (<0.1st percentile), which prompted more frequent patient follow-up. Oligohydramnios was detected at 38 weeks and 1 day, and labor was induced. An infant with birthweight in the 12th percentile for gestational age was born. We learned that EPV can precede intrauterine growth restriction (IUGR), oligohydramnios, and low birthweight.

Retained Placenta Percreta with Acquired Uterine Arteriovenous Malformation—Case Report and Short Review of the Literature

Placenta accreta spectrum disorder (PAS) has an increased frequency due to the high number of cesarean sections. The abnormal placentation associated with a retained placenta can cause persistent uterine bleeding, with ultrasound Doppler examination being the main choice to assess the uterine hemorrhage. An acquired uterine arteriovenous malformation (AVM) may occur because of uterine trauma, spontaneous abortion, dilation and curettage, endometrial carcinoma or gestational trophoblastic disease. The treatment for abnormal placentation associated with AVM can be conservative, represented by methotrexate therapy, arterial embolization, uterine curettage, hysteroscopic loop resection or radical, which takes into consideration total hysterectomy. Therapeutic management always considers the degree of placental invasion, the patient hemodynamic state and fertility preservation. Considering the aspects described, we present a case of retained placenta percreta associated with acquired uterine AVM, with imagistic and clinical features suggestive of a gestational trophoblastic disease, successfully treated by hysterectomy, along with a small review of the literature, as only a few publications have reported a similar association of diagnostics and therapy.

Early Gestational Age Placenta Accreta Case Report: Can We Avoid Missed Diagnosis?

Case series

Patients: Female, 34-year-old • Female, 35-year-old • Female, 32-year-old

Final Diagnosis: Placenta accrete

Symptoms: Vaginal bleeding

Medication: —

Clinical Procedure: —

Specialty: Obstetrics and Gynecology

Maternal PM2.5 exposure and abnormal placental nutrient transport

Epidemiological studies of human and animal experiments indicated that gestational exposure to atmospheric pollutants could be followed by the abnormal placental development. However, the effects of this exposure on the placental transportation for nutrients have not been systematically investigated. In this study, fine particulate matters (PM_2.5) samples were collected in Taiyuan and pregnant rodent models were administered with 3 mg/kg b.w. PM_2.5 by oropharyngeal aspiration every other day starting on embryonic day 0.5 (E0.5). Then the pregnant mice were sacrificed and their placentas were collected at different time points. The results showed that maternal PM_2.5 exposure (MPE) disrupted the expression of proliferating cell nuclear antigen (PCNA) at all time points and inhibited the cell proliferation in placenta. Following that, the capacity for placental nutrient transport was impaired. The changes at E18.5 were observed most significantly, showing the altered mRNA expression of amino acid, long-chain polyunsaturated fatty acid (LCPUFA), glucose and folate transporters. In addition, the glycogen content was elevated at E18.5, and the triglyceride content was increased at E13.5 and E15.5 and decreased at E18.5 in the placenta after MPE. In a word, the adverse effect induced by MPE revealed that MPE led tothe disruption on the nutrient supply to the developing fetus via modulating the abundance of placental nutrient transporters (PNT).

How to read a fetal magnetic resonance image 101

Accurate antenatal diagnosis is essential for planning appropriate pregnancy management and improving perinatal outcomes. The provision of information vital for prognostication is a crucial component of prenatal imaging, and this can be enhanced by the use of fetal MRI. Image acquisition, interpretation and reporting of a fetal MR study can be daunting to the individual who has encountered few or none of these examinations. This article provides the radiology trainee with a general approach to interpreting a fetal MRI. The authors review the added value of prenatal MRI in the overall assessment of fetal wellbeing, discuss MRI protocols and techniques, and review the normal appearance of maternal and fetal anatomy. The paper concludes with a sample template for structured reporting, to serve as a checklist and guideline for reporting radiologists.

Inter- and Intraobserver Agreement in First Trimester Ultrasound Evaluation of Placental Biometry

OBJECTIVE

The aim of this study was to assess the clinical applicability of a new analytical software program by determining the inter- and intraobserver agreement for 2D placental biometry and three-dimensional (3D) placental volume (PV) in the first trimester.

METHODS

A prospective study of 25 singleton pregnancies between 11 and 14 weeks was conducted. 3D datasets were captured, and PV was estimated using the Phillips QLAB GI3DQ ultrasound quantification software. The basal plate (BP), chorionic plate (CP), placental thickness (PT), and the free uterine surface (FUS) area not occupied by placenta were considered for 2D biometry evaluation. Each variable was measured in 2 orthogonal planes with mean values used for the analysis. Intra- and interobserver agreement was evaluated.

RESULTS

Intraobserver agreement for both 2D and 3D measurements was high, particularly for the PV and PT (interclass correlation coefficient [ICC] 0.989 [95% confidence interval (CI) 0.97-0.99] and ICC 0.936 [95% CI 0.86-0.97], respectively). Interobserver agreement was good for the PV (ICC 0.963 [95% CI 0.91-0.98]), PT (ICC 0.822 [95% CI 0.63-0.91]), and CP (ICC 0.708 [95% CI 0.44-0.86]), but moderate for BP and FUS.

CONCLUSIONS

PV, PT, and CP are reproducible measurements to evaluate first trimester placental biometry. Further research is needed to assess the clinical utility of these variables as predictors of poor obstetric outcomes.

Characterizing placental stiffness using ultrasound shear-wave elastography in healthy and preeclamptic pregnancies

PURPOSE

To measure the stiffness of the placenta in healthy and preeclamptic patients in the second and third trimesters of pregnancy using ultrasound shear-wave elastography (SWE). We also aimed to evaluate the effect of age, gestational age, gravidity, parity and body mass index (BMI) on placental stiffness and a possible correlation of stiffness with perinatal outcomes.

METHODS

In a case-control study, we recruited a total of 47 singleton pregnancies in the second and third trimesters of which 24 were healthy and 23 were diagnosed with preeclampsia. In vivo placental stiffness was measured once at the time of recruitment for each patient. Pregnancies with posterior placentas, multiple gestation, gestational hypertension, chronic hypertension, diabetes, autoimmune disease, fetal growth restriction and congenital anomalies were excluded.

RESULTS

The mean placental stiffness was significantly higher in preeclamptic pregnancies compared to controls in the third trimester (difference of means = 16.8; 95% CI (9.0, 24.5); P < 0.001). There were no significant differences in placental stiffness between the two groups in the second trimester or between the severe preeclampsia and preeclampsia without severe features groups (difference of means = 9.86; 95% CI (-5.95, 25.7); P ≥ 0.05). Peripheral regions of the placenta were significantly stiffer than central regions in the preeclamptic group (difference of means = 10.67; 95% CI (0.07, 21.27); P < 0.05), which was not observed in the control group (difference of means = 0.55; 95% CI (- 5.25, 6.35); P > 0.05). We did not identify a correlation of placental stiffness with gestational age, maternal age, gravidity or parity. However, there was a statistically significant correlation with BMI (P < 0.05). In addition, pregnancies with higher placental stiffness during the 2nd and 3rd trimesters had significantly reduced birth weight (2890 ± 176 vs. 2420 ± 219 g) and earlier GA (37.8 ± 0.84 vs. 34.3 ± 0.98 weeks) at delivery (P < 0.05).

CONCLUSION

Compared to healthy pregnancies, placentas of preeclamptic pregnancies are stiffer and more heterogeneous. Placental stiffness is not affected by gestational age or the severity of preeclampsia but there is a correlation with higher BMI and poor perinatal outcomes.

Diffusion-weighted imaging of placenta in intrauterine growth restriction with worsening Doppler US findings

PURPOSE

We aimed to compare the placental diffusion difference between intrauterine growth restriction (IUGR) patients with worsening Doppler ultrasonography (US) findings and control group with normal Doppler US findings by using diffusion-weighted imaging (DWI).

METHODS

We performed a prospective study to compare the placental diffusion difference in 63 patients (gestational week, 28-34 weeks), including 50 IUGR patients (mean gestational week, 30 weeks 3 days ±16.2 days) with worsening Doppler US findings and 13 patients with normal Doppler US findings (mean gestational week, 29 weeks 4 days ±12.3 days) by using DWI (b value, 0-1000 s/mm2). We classified IUGR patients into three groups according to the reference values of the umbilical artery pulsatility index (PI) chart. Placenta apparent diffusion coefficient (ADC) calculations were performed by freehand drawn regions-of-interest (ROIs) (min, 8.04 cm2; max, 200 cm2).

RESULTS

Placental ADC values in IUGR patients (mean, 1.624±0.181 ×10-³ mm²/s; range, 1.35-1.96 ×10-3 mm2/s) were significantly reduced compared with the control group (mean, 1.827±0.191 ×10-³ mm²/s; range, 1.35-2.84 ×10-3 mm2/s) (P = 0.001). For adjusted ROI area calculation, ADC values were significantly lower in groups 3, 2 and 1, respectively, compared with the control group (P < 0.05); and there was no significant difference between groups 1 and 2 (P > 0.05). Preeclampsia significantly reduced the placental diffusion compared with patients without preeclampsia (P = 0.003). Gestational aging did not significantly affect ADC values in control patients (r=0.08, P = 0.561). The sensitivity, specificity, negative and positive predictive values of ADC to detect IUGR were 72%, 84.6%, 44%, and 94.7% with a cutoff value of 1.727 ×10-3 mm2/s, respectively.

CONCLUSION

The diagnostic estimation of placental ADC values to predict the severity of IUGR is comparable to that of umbilical artery PI. Considering that at the very early onset of IUGR, placental diffusion diminishes, ADC as a marker for IUGR in lieu of umbilical artery PI has the potential to determine the threshold for decreased placental diffusion. Therefore, DWI should be added to routine fetal MRI to show diffusion changes in placenta.

Large placental chorioangioma: a potential effective in-utero treatment modality for radio frequency ablation

Background

Placenta chorioangiomas are common benign placental tumours. While microscopic chorioangiomas are frequent, macroscopic chorioangiomas of more than 5 cm are rare and often associated with fetal complications such as high output cardiac failure, fetal anaemia and stillbirth. Close monitoring and in-utero treatment are sometimes necessary to prevent adverse pregnancy outcome.

Case presentation

We present two cases of large placenta chorioangiomas with one case requiring surgical therapy with radiofrequency ablation (RFA) of tumour vessels, which resulted in a successful outcome of a live birth at term.

Conclusion

We conclude that RFA is an effective alternative treatment modality to fetoscopic laser therapy in utero for cases at risk of fetal cardiac failure and intrauterine demise in the presence of large chorioangiomas.

MRI evaluation of the placenta from normal variants to abnormalities of implantation and malignancies

Even though the placenta has been known for millennia, it is still considered one of the most complex and least understood human organs. Imaging of the placenta is gaining attention due to its impact on fetal and maternal outcomes. MRI plays a vital role in evaluation of inconclusive cases by ultrasonography. It enables precise mapping of placental abnormalities for proper multidisciplinary planning and management. In this article we provide a comprehensive in-depth review of the role of antenatal MR in evaluating "The Placenta." We will describe the protocols and techniques used for MRI of the placenta, review anatomy of the placenta, describe MRI features of major placental abnormalities including those related to position, depth of implantation, hemorrhage, gestational trophoblastic neoplasia, and retained products of conception and discuss the added value of MRI in the management and preoperative planning of such abnormalities. Level of Evidence: 3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;50:1702-1717.

Perinatal outcome and long-term pediatric morbidity of pregnancies with a fibroid uterus

BACKGROUND

Uterine fibroids are a common morbidity in women and its prevalence is increasing with age. As maternal age rises, fibroids become more prevalent during pregnancy.

AIM

To assess perinatal outcome and long-term health of children to mothers with uterine fibroids during pregnancy.

STUDY DESIGN

A population-based cohort analysis assessing long-term hospitalizations of offspring, up to the age of 18 years, due to gastrointestinal, neurological, cardiovascular, endocrine, and respiratory morbidity, following pregnancies diagnosed with and without a fibroid uterus. Multivariable generalized estimating equation (GEE) analysis adjusted for maternal clusters and other possible confounders was performed. Kaplan-Meier survival curves and Cox survival regression models were used to compare cumulative morbidity incidence and control for confounders.

SUBJECTS

All singleton deliveries occurring between 1991 and 2014.

OUTCOME MEASURES

Perinatal outcome and long-term pediatric morbidity.

RESULTS

A total of 242,445 singleton deliveries were included; 0.5% of which were diagnosed with uterine fibroids (n = 1237). In the GEE multivariable analyses, advanced maternal age, hypertensive disorder and diabetes mellitus, fetal growth restriction, low birthweight (<2500 g), and small for gestational age newborns, were all independently associated with uterine fibroids during pregnancy. Hospitalizations up to the age of 18 years in the different health categories were comparable between the groups, using Cox regression models, controlled for clinically significant confounders in the long-term outcomes.

CONCLUSION

Maternal uterine fibroids appear to negatively impact perinatal outcome, mainly fetal growth. However, no independent major impact on future health of the offspring can be detected.

Effect of Fine Particulate Matter (PM2.5) on Rat Placenta Pathology and Perinatal Outcomes

Background

Fine particulate matter with aerodynamic diameters smaller than 2.5 μm (PM_2.5) has been reported to cause adverse effects on human health. Evidence has shown the association between PM_2.5 exposure and adverse perinatal outcomes, and the most common method is epidemiological investigation. We wished to investigate the impact of PM_2.5 on placenta and prenatal outcomes and its related mechanisms in a rat model.

Material/Methods

Pregnant rats were exposed to a low PM_2.5 dose (15 mg/kg) with intratracheal instillation at pregnant day 10 and day 18, while the controls received an equivalent volume normal saline. All rats received cesarean section 24 h after the last intratracheal instillation and were sacrificed with anesthesia. Blood routine tests (BRT) and interleukin-6 (IL-6) were detected for analyzing inflammation and blood coagulation. Placenta tissue sections underwent pathologic examination, and the levels of homogenate glutathione peroxidase (GSH-Px) and methane dicarboxylic aldehyde (MDA) were determined for oxidative stress estimation.

Results

Increased absorbed blastocysts, and lower maternal weight gain and fetal weight were found in the PM_2.5 exposure group compared to controls (p<0.05). Exposure to PM_2.5 caused a significant increase of blood mononuclear cells (PBMC), platelets, and IL-6 levels (P<0.01). There were no differences in GSH-Px and MDA of placenta homogenate between the 2 groups (P>0.05). Placenta pathological examination demonstrated thrombus and chorioamnionitis in the PM_2.5 exposure group.

Conclusions

PM_2.5 exposure can result in placental pathological changes and adverse perinatal outcomes. The placental inflammation and hypercoagulability with vascular thrombosis may play important roles in placental impairment, but oxidative stress appears to be less important.

Relationship between Plasma D-Dimer Concentration and Three-Dimensional Ultrasound Placental Volume in Women at Risk for Placental Vascular Diseases: A Monocentric Prospective Study

Introduction

The aim of this study was to correlate placental volumes deduced from three-dimensional ultrasound and virtual organ computer-aided analysis (VOCAL) software with systemic concentrations of D-dimer and soluble endothelial protein C receptor (sEPCR).

Methods

This was a monocentric experimental prospective study conducted from October 2008 to July 2009. Forty consecutive patients at risk of placental vascular pathology (PVP) recurrence or occurrence were included. Placental volumes were systematically measured three times (11–14, 16–18 and 20–22 weeks of gestation (WG)) by two independent sonographers. D-dimers and sEPCR plasma concentrations were measured using ELISA kits (Enzyme Linked ImmunoSorbent Assay).

Results

Eleven patients had a PVP. The plasma D-dimer level was positively correlated with placental volume (r = 0.45, p < 0.001). A smaller placental volume and placental quotient was evidenced in women who developed a PVP at the three gestational ages, and the difference was more pronounced during the third exam (20 WG). No obvious correlation could be demonstrated between the development of a PVP and the levels of D-dimer and sEPCR. There was no significant difference in the values of placental volumes measured by the two sonographers.

Conclusion

The placenta growth could be a major determinant of the elevation of D-dimer during pregnancy. Consideration of placental volume could allow for modulation of the D-dimer concentrations for restoring their clinical interest.

Animal Models to Study Placental Development and Function throughout Normal and Dysfunctional Human Pregnancy

Abnormalities of placental development and function are known to underlie many pathologies of pregnancy, including spontaneous preterm birth, fetal growth restriction, and preeclampsia. A growing body of evidence also underscores the importance of placental dysfunction in the lifelong health of both mother and offspring. However, our knowledge regarding placental structure and function throughout pregnancy remains limited. Understanding the temporal growth and functionality of the human placenta throughout the entirety of gestation is important if we are to gain a better understanding of placental dysfunction. The utilization of new technologies and imaging techniques that could enable safe monitoring of placental growth and function in vivo has become a major focus area for the National Institutes of Child Health and Human Development, as evident by the establishment of the "Human Placenta Project." Many of the objectives of the Human Placenta Project will necessitate preclinical studies and testing in appropriately designed animal models that can be readily translated to the clinical setting. This review will describe the advantages and limitations of relevant animals such as the guinea pig, sheep, and nonhuman primate models that have been used to study the role of the placenta in fetal growth disorders, preeclampsia, or other maternal diseases during pregnancy.

Is Doppler ultrasound useful for evaluating gestational trophoblastic disease?

Doppler ultrasound is a non-invasive method for evaluating vascularization and is widely used in clinical practice. Gestational trophoblastic neoplasia includes a group of highly vascularized malignancies derived from placental cells. This review summarizes data found in the literature regarding the applications of Doppler ultrasound in managing patients with gestational trophoblastic neoplasia. The PubMed/Medline, Web of Science, Cochrane and LILACS databases were searched for articles published in English until 2014 using the following keywords: "Gestational trophoblastic disease AND Ultrasonography, Doppler." Twenty-eight articles met the inclusion criteria and were separated into the 4 following groups according to the aim of the study. (1) Doppler ultrasound does not seem to be capable of differentiating partial from complete moles, but it might be useful when evaluating pregnancies in which a complete mole coexists with a normal fetus. (2) There is controversy in the role of uterine artery Doppler velocimetry in the prediction of development of gestational trophoblastic neoplasia. (3) Doppler ultrasound is a useful tool in the diagnosis of gestational trophoblastic neoplasia because abnormal myometrial vascularization and lower uterine artery Doppler indices seem to be correlated with invasive disease. (4) Lower uterine artery Doppler indices in the diagnosis of gestational trophoblastic neoplasia are associated with methotrexate resistance and might play a role in prognosis.

CONCLUSION

Several studies support the importance of Doppler ultrasound in the management of patients with gestational trophoblastic neoplasia, particularly the role of Doppler velocimetry in the prediction of trophoblastic neoplasia and the chemoresistance of trophoblastic tumors. Doppler findings should be used as ancillary tools, along with human chorionic gonadotropin assessment, in the diagnosis of gestational trophoblastic neoplasia.

Retained Placenta Accreta Mimicking Choriocarcinoma

This case demonstrates a rare event of retained invasive placenta masquerading as choriocarcinoma. The patient presented with heavy vaginal bleeding following vaginal delivery complicated by retained products of conception. Ultrasound and computed tomography demonstrated a vascular endometrial mass, invading the uterine wall and raising suspicion for choriocarcinoma. Hysterectomy revealed retained invasive placenta.

Hyperpolarized [1-(13) C]pyruvate MRI for noninvasive examination of placental metabolism and nutrient transport: A feasibility study in pregnant guinea pigs

PURPOSE

To test the feasibility of hyperpolarized [1-(13) C]pyruvate magnetic resonance imaging (MRI) for noninvasive examination of guinea pig fetoplacental metabolism and nutrient transport.

MATERIALS AND METHODS

Seven pregnant guinea pigs with a total of 30 placentae and fetuses were anesthetized and scanned at 3T. T1 -weighted (1) H images were obtained from the maternal abdomen. An 80 mM solution of hyperpolarized [1-(13) C]pyruvate (hereafter referred to as pyruvate) was injected into a vein in the maternal foot. Time-resolved 3D (13) C images were acquired starting 10 seconds after the beginning of bolus injection and every 10 seconds after to 50 seconds. The pregnant guinea pigs were recovered after imaging. Regions of interest (ROIs) were drawn around the maternal heart and each placenta and fetal liver in all slices in the (1) H images. These ROIs were copied to the (13) C images and were used to calculate the sum of the pyruvate and lactate signal intensities for each organ. The signal intensities were normalized by the volume of the organ and the maximum signal in the maternal heart.

RESULTS

No adverse events were observed in the pregnant guinea pigs and natural pupping occurred at term (∼68 days). Pyruvate signal was observed in all 30 placentae, and lactate, a by-product of pyruvate metabolism, was also observed in all placentae. The maximum pyruvate and lactate signals in placentae occurred at 20 seconds. In addition to the observation of pyruvate and lactate signals in the placentae, both pyruvate and lactate signals were observed in all fetal livers. The maximum pyruvate and lactate signals in the fetal livers occurred at 10 seconds and 20 seconds, respectively.

CONCLUSION

This work demonstrates the feasibility of using hyperpolarized [1-(13) C]pyruvate MRI to noninvasively examine fetoplacental metabolism and transport of pyruvate in guinea pigs. Hyperpolarized (13) C MRI may provide a novel method for longitudinal studies of fetoplacental abnormalities.

Extrafetal Findings on Fetal Magnetic Resonance Imaging: A Pictorial Essay

Although US is the mainstay of fetal imaging, magnetic resonance imaging (MRI) has become an invaluable adjunct in recent years. MRI offers superb soft tissue contrast that allows for detailed evaluation of fetal organs, particularly the brain, which enhances understanding of disease severity. MRI can yield results that are similar to or even better than those of US, particularly in cases of marked oligohydramnios, maternal obesity, or adverse fetal positioning. Incidentally detected extrafetal MRI findings are not uncommon and may affect clinical care. Physicians interpreting fetal MRI studies should be aware of findings occurring outside the fetus, including those structures important for the pregnancy. A systematic approach is necessary in the reading of such studies. This helps to ensure that important findings are not missed, appropriate clinical management is implemented, and unnecessary follow-up examinations are avoided. In this pictorial essay, the most common extrafetal abnormalities are described and illustrated.

Routine ultrasound in late pregnancy (after 24 weeks' gestation)

BACKGROUND

Diagnostic ultrasound is used selectively in late pregnancy where there are specific clinical indications. However, the value of routine late pregnancy ultrasound screening in unselected populations is controversial. The rationale for such screening would be the detection of clinical conditions which place the fetus or mother at high risk, which would not necessarily have been detected by other means such as clinical examination, and for which subsequent management would improve perinatal outcome.

OBJECTIVES

To assess the effects on obstetric practice and pregnancy outcome of routine late pregnancy ultrasound, defined as greater than 24 weeks' gestation, in women with either unselected or low-risk pregnancies.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2015) and reference lists of retrieved studies.

SELECTION CRITERIA

All acceptably controlled trials of routine ultrasound in late pregnancy (defined as after 24 weeks).

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy.

MAIN RESULTS

Thirteen trials recruiting 34,980 women were included in the systematic review. Risk of bias was low for allocation concealment and selective reporting, unclear for random sequence generation and incomplete outcome data and high for blinding of both outcome assessment and participants and personnel. There was no difference in antenatal, obstetric and neonatal outcome or morbidity in screened versus control groups. Routine late pregnancy ultrasound was not associated with improvements in overall perinatal mortality. There is little information on long-term substantive outcomes such as neurodevelopment. There is a lack of data on maternal psychological effects.Overall, the evidence for the primary outcomes of perinatal mortality, preterm birth less than 37 weeks, induction of labour and caesarean section were assessed to be of moderate or high quality with GRADE software. There was no association between ultrasound in late pregnancy and perinatal mortality (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.67 to 1.54; participants = 30,675; studies = eight; I² = 29%), preterm birth less than 37 weeks (RR 0.96, 95% CI 0.85 to 1.08; participants = 17,151; studies = two; I² = 0%), induction of labour (RR 0.93, 95% CI 0.81 to 1.07; participants = 22,663; studies = six; I² = 78%), or caesarean section (RR 1.03, 95% CI 0.92 to 1.15; participants = 27,461; studies = six; I² = 54%). Three additional primary outcomes chosen for the 'Summary of findings' table were preterm birth less than 34 weeks, maternal psychological effects and neurodevelopment at age two. Because none of the included studies reported these outcomes, they were not assessed for quality with GRADE software.

AUTHORS' CONCLUSIONS

Based on existing evidence, routine late pregnancy ultrasound in low-risk or unselected populations does not confer benefit on mother or baby. There was no difference in the primary outcomes of perinatal mortality, preterm birth less than 37 weeks, caesarean section rates, and induction of labour rates if ultrasound in late pregnancy was performed routinely versus not performed routinely. Meanwhile, data were lacking for the other primary outcomes: preterm birth less than 34 weeks, maternal psychological effects, and neurodevelopment at age two, reflecting a paucity of research covering these outcomes. These outcomes may warrant future research.

Fetal MRI: A Technical Update with Educational Aspirations

Fetal magnetic resonance imaging (MRI) examinations have become well-established procedures at many institutions and can serve as useful adjuncts to ultrasound (US) exams when diagnostic doubts remain after US. Due to fetal motion, however, fetal MRI exams are challenging and require the MR scanner to be used in a somewhat different mode than that employed for more routine clinical studies. Herein we review the techniques most commonly used, and those that are available, for fetal MRI with an emphasis on the physics of the techniques and how to deploy them to improve success rates for fetal MRI exams. By far the most common technique employed is single-shot T2-weighted imaging due to its excellent tissue contrast and relative immunity to fetal motion. Despite the significant challenges involved, however, many of the other techniques commonly employed in conventional neuro- and body MRI such as T1 and T2*-weighted imaging, diffusion and perfusion weighted imaging, as well as spectroscopic methods remain of interest for fetal MR applications. An effort to understand the strengths and limitations of these basic methods within the context of fetal MRI is made in order to optimize their use and facilitate implementation of technical improvements for the further development of fetal MR imaging, both in acquisition and post-processing strategies.

MANAGEMENT OF REDUCED FETAL MOVEMENTS

Reduced fetal movement (RFM) is commonly defined as any reduction in maternal perception of fetal activity. Perceived fetal activity may be movement of limbs, trunk or head movement, but excludes fetal hiccoughs (as this is involuntary movement). The perception of fetal movement by an expectant mother is the first, and ongoing, non-sonographic indicator of fetal viability. The “normal” pattern of fetal movements varies from pregnancy to pregnancy, and often does not become established until 28 weeks’ gestation. Many babies have particularly active periods of the day, usually corresponding to periods of maternal rest and inactivity (which may in itself reflect increased maternal awareness of fetal movement). A variable percentage of sonographically observed fetal movements are perceived by prospective mothers (commonly 30–40%, although some studies report rates as high as 80%).

Three-dimensional Evaluation of the Placenta: Review of the Literature

The introduction of the three-dimensional (3D) ultrasound made feasible the quantitative and qualitative evaluation of the placenta's characteristics like the volume, the surface rendered imaging, the vascularization and the blood flow. These novel techniques may assist the early detection of pregnancies at high risk for fetal growth restriction (FGR), pre-eclampsia (PET) and pregnancy-induced hypertension (PIH) and help clinicians to detect pregnancies at risk earlier and to assess new therapeutic strategies in order to prevent adverse pregnancy outcomes. However, in this new technique there are still limitations regarding the assessment of the placenta employing 3D ultrasound in everyday clinical practice. In the following article, we perform a review of the literature regarding the importance of 3D evaluation of the placenta in pregnancy.

How to cite this article

Natsis S, Antsaklis P, Antsaklis A, Kurjak A. Three-dimensional Evaluation of the Placenta: Review of the Literature. Donald School J Ultrasound Obstet Gynecol 2013;7(1):73-79.

Imaging and assessment of placental function

The placenta is the vital support organ for the developing fetus. This article reviews current ultrasound (US) methods of assessing placental function. The ability of ultrasound to detect placental pathology is discussed. Doppler technology to investigate the fetal, placental, and maternal circulations in both high-risk and uncomplicated pregnancies is discussed and the current literature on the value of three-dimensional power Doppler studies to assess placental volume and vascularization is also evaluated. The article highlights the need for further research into three-dimensional ultrasound and alternative methods of placental evaluation if progress is to be made in optimizing placental function assessment.

Comparative analysis of placental vasculature and placental volume in normal and IUGR pregnancies with the use of three-dimensional Power Doppler

Objectives

To evaluate the differences in placental vascular indices and placental volume between normal and IUGR pregnancies.

Methods

A prospective study was conducted on a group of 100 normal and 20 IUGR pregnancies between 22 and 42 weeks of gestation. For the purpose of evaluation of placental volume and placental vascular indices, we applied 3D Power Doppler and VOCAL technique. Only patients with entirely visualized placenta were included in the study.

Results

A comparative analysis of vascularization index (VI), vascularization flow index (VFI), flow index (FI), and placental volume (PV) revealed statistically significant differences between normal and IUGR pregnancies.

In normal pregnancies, the volume of the placenta was on average 92.42 cm³ larger than in pregnancies complicated by IUGR. Receiver operating characteristic (ROC) curves were used to evaluate the clinical usefulness of placental vascular indices and placental volume for discriminating IUGR and normal pregnancies. It was concluded that the VI, VFI, PV, FI parameters are the best discriminants, with the cut-off values of 5.30, 2.30, 199, and 36.0, respectively.

Conclusions

The quantitative assessment of placental vasculature and placental volume by means of 3D Power Doppler and VOCAL technique is an adjunctive modality for differentiation between normal and IUGR pregnancies. Our findings further suggest that the vascularization index (VI) and vascularization flow index (VFI) are the best parameters with the most favorable discriminating potential for proper identification of IUGR pregnancies.

Magnetic resonance imaging of the placenta identifies placental vascular abnormalities independently of Doppler ultrasound

OBJECTIVE

To evaluate the relationship between placental vascular pathology detected by prenatal magnetic resonance imaging (MRI) and perinatal outcome.

METHODS

This was a retrospective, hospital-based, cross-sectional study in which all fetal MRI examinations of singleton pregnancies with vascular placental pathology (i.e. infarction with/without hemorrhage, subchorionic thrombi/hemorrhages, intervillous thrombi/hemorrhages, or retroplacental hematoma) in the period 2002-2007 were included. The extent of the pathology was expressed as a percentage of the total placental volume. Abnormalities of umbilical artery Doppler ultrasound examinations within 7 days between MRI and ultrasound examination were noted. Death in utero or postnatally was the primary outcome. Gestational age at MRI and at birth and the occurrence of intrauterine growth restriction (IUGR) were noted. Logistic regression analysis was performed to assess the impact of gestational age at MRI, extent of the vascular lesion and presence of pathological Doppler ultrasound measurements on the prediction of mortality.

RESULTS

Fifty-nine structurally normal singleton pregnancies with placental vascular abnormalities were included in the analysis. Mortality rate was 36%; among the survivors, 87% were born before 37 + 0 gestational weeks and 50% suffered from IUGR. In 55% of the pregnancies pathological umbilical artery Doppler findings were identified, of which 27% were non-survivors. Mortality was predicted by earlier gestational age at fetal MRI for placental pathology (P < 0.05) and increasing extent of the vascular lesion (P < 0.05), but not by the presence of pathological Doppler ultrasound data. Accuracy of the prediction was 82%, sensitivity was 67% and specificity 89%.

CONCLUSION

MRI-detected vascular placental pathologies may help to identify pregnancies at risk for adverse outcome and fetal death independently of umbilical artery Doppler status.

Terminal monosaccharide expression on amniotic glycoproteins as biomarkers of fetus maturity

Glycotypes, particularly those that terminate with sialic acid and fucose are known to play a fundamental role in human development, during implantation, growth and differentiation of fetal tissues. The present review describes changes in the exposition of terminal sialic acid and fucose isoforms in the amniotic fluid glycoconjugates, α1-acid glycoprotein and fibronectin during critical stages of pregnancy, i.e. second and third trimester, perinatal period, delivery and post-date pregnancy. The distinct amniotic glycoforms are suggested to be implicated in regulatory processes to ensure homoeostasis during pregnancy and to protect the fetus. These may have the potential of becoming additional laboratory makers in obstetrics to monitor pregnancy.

Dynamic contrast-enhanced magnetic resonance imaging: definitive imaging of placental function?

The placenta constitutes a complex circulatory interface between the mother and fetus, but the relationship between the maternal and fetal circulation is still very difficult to study in vivo. There is growing evidence that magnetic resonance imaging (MRI) is useful and safe during pregnancy, and MRI is increasingly used for fetal and placental anatomical imaging. MRI functional imaging is now a modern obstetric tool and has the potential to provide new insights into the physiology of the human placenta. Placental perfusion has been studied during the first pass of an MR contrast agent, by arterial spin labeling, diffusion imaging, T1 and T2 relaxation time measurement using echo-planar imaging, and by a combination of magnetization transfer with established stereological methods. The BOLD (blood oxygen level-dependent) effect offers new perspectives for functional MRI evaluation of the placenta.

Diffusion-weighted MR imaging of the placenta in fetuses with placental insufficiency

PURPOSE

To evaluate diffusion-weighted magnetic resonance (MR) imaging of the human placenta in fetuses with and fetuses without intrauterine growth restriction (IUGR) who were suspected of having placental insufficiency.

MATERIALS AND METHODS

The study was approved by the local ethics committee, and written informed consent was obtained. The authors retrospectively evaluated 1.5-T fetal MR images from 102 singleton pregnancies (mean gestation ± standard deviation, 29 weeks ± 5; range, 21-41 weeks). Morphologic and diffusion-weighted MR imaging were performed. A region of interest analysis of the apparent diffusion coefficient (ADC) of the placenta was independently performed by two observers who were blinded to clinical data and outcome. Placental insufficiency was diagnosed if flattening of the growth curve was detected at obstetric ultrasonography (US), if the birth weight was in the 10th percentile or less, or if fetal weight estimated with US was below the 10th percentile. Abnormal findings at Doppler US of the umbilical artery and histopathologic examination of specimens from the placenta were recorded. The ADCs in fetuses with placental insufficiency were compared with those in fetuses of the same gestational age without placental insufficiency and tested for normal distribution. The t tests and Pearson correlation coefficients were used to compare these results at 5% levels of significance.

RESULTS

Thirty-three of the 102 pregnancies were ultimately categorized as having an insufficient placenta. MR imaging depicted morphologic changes (eg, infarction or bleeding) in 27 fetuses. Placental dysfunction was suspected in 33 fetuses at diffusion-weighted imaging (mean ADC, 146.4 sec/mm(2) ± 10.63 for fetuses with placental insufficiency vs 177.1 sec/mm(2) ± 18.90 for fetuses without placental insufficiency; P < .01, with one false-positive case). The use of diffusion-weighted imaging in addition to US increased sensitivity for the detection of placental insufficiency from 73% to 100%, increased accuracy from 91% to 99%, and preserved specificity at 99%.

CONCLUSION

Placental dysfunction associated with growth restriction is associated with restricted diffusion and reduced ADC. A decreased ADC used as an early marker of placental damage might be indicative of pregnancy complications such as IUGR.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10092283/-/DC1.

Evaluation of placental maturity by the sonographic textures

PURPOSE

Routine ultrasound screening to predict gestational age is important for risk assessment of pregnancy complications among pregnant women. We explored a quantitative method for sonographic analysis of placental texture, with the objective of reproducible measurement.

METHODS

We studied 151 pregnant women; the gestational ages of their fetuses ranged from 10 to 38 weeks. Three experienced sonographers delineated the placental contour to define the region of interest (ROI). From these sonograms, 72 texture features were derived from the spatial gray-level dependence matrices and gray-level difference matrices. We used these as input variables in a multiple linear regression analysis.

RESULTS

A significant positive correlation (P < 0.01) was found between the multiple linear regression results and the corresponding gestation ages by the three assessors (r (A) = 0.755, r (B) = 0.851, and r (C) = 0.832). We also found good agreement between multiple linear regression results for the three observers. Their κ statistic values were 0.685 between assessors A and B, 0.679 between A and C, and 0.804 between B and C.

CONCLUSION

Quantitative sonography using texture analysis of the placenta was useful in practice to determine gestational age.

Magnetic resonance imaging of hypoxic injury to the murine placenta

We assessed the use of magnetic resonance imaging (MRI) to define placental hypoxic injury associated with fetal growth restriction. On embryonic day 18.5 (E18.5) we utilized dynamic contrast-enhanced (DCE)-MRI on a 4.7-tesla small animal scanner to examine the uptake and distribution of gadolinium-based contrast agent. Quantitative DCE parameter analysis was performed for the placenta and fetal kidneys of three groups of pregnant C57BL/6 mice: 1) mice that were exposed to Fi(O(2)) = 12% between E15.5 and E18.5, 2) mice in normoxia with food restriction similar to the intake of hypoxic mice between E15.5 and E18.5, and 3) mice in normoxia that were fed ad libitum. After imaging, we assessed fetoplacental weight, placental histology, and gene expression. We found that dams exposed to hypoxia exhibited fetal growth restriction (weight reduction by 28% and 14%, respectively, P < 0.05) with an increased placental-to-fetal ratio. By using MRI-based assessment of placental contrast agent kinetics, referenced to maternal paraspinous muscle, we found decreased placental clearance of contrast media in hypoxic mice, compared with either control group (61%, P < 0.05). This was accompanied by diminished contrast accumulation in the hypoxic fetal kidneys (23%, P < 0.05), reflecting reduced transplacental gadolinium transport. These changes were associated with increased expression of placental Phlda2 and Gcm1 transcripts. Exposure to hypoxia near the end of mouse pregnancy reduces placental perfusion and clearance of contrast. MRI-based DCE imaging provides a novel tool for dynamic, in vivo assessment of placental function.

Routine ultrasound in late pregnancy (after 24 weeks' gestation)

BACKGROUND

Diagnostic ultrasound is used selectively in late pregnancy where there are specific clinical indications. However, the value of routine late pregnancy ultrasound screening in unselected populations is controversial. The rationale for such screening would be the detection of clinical conditions which place the fetus or mother at high risk, which would not necessarily have been detected by other means such as clinical examination, and for which subsequent management would improve perinatal outcome.

OBJECTIVES

To assess the effects on obstetric practice and pregnancy outcome of routine late pregnancy ultrasound, defined as greater than 24 weeks' gestation, in women with either unselected or low-risk pregnancies.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (February 2008).

SELECTION CRITERIA

All acceptably controlled trials of routine ultrasound in late pregnancy (defined as after 24 weeks).

DATA COLLECTION AND ANALYSIS

All three review authors were involved in assessing trial quality and data extraction.

MAIN RESULTS

Eight trials recruiting 27,024 women were included. The quality of trials overall was satisfactory. There was no difference in antenatal, obstetric and neonatal intervention or morbidity in screened versus control groups. There was a slightly higher caesarean section rate in the screened group, but this difference did not reach statistical significance. Routine late pregnancy ultrasound was not associated with improvements in overall perinatal mortality. Placental grading as an adjunct to third trimester examination scan was associated with a significant reduction in the stillbirth rate in the one trial that assessed it. There is little information on long-term substantive outcomes such as neurodevelopment. There is a lack of data on maternal psychological effects.

AUTHORS' CONCLUSIONS

Based on existing evidence, routine late pregnancy ultrasound in low-risk or unselected populations does not confer benefit on mother or baby. It may be associated with a small increase in caesarean section rates. There is a lack of data about the potential psychological effects of routine ultrasound in late pregnancy, and limited data about its effects on both short- and long-term neonatal and childhood outcome. Placental grading in the third trimester may be valuable, but whether reported results are reproducible remains to be seen, and future research of late pregnancy ultrasound should include evaluation of placental textural assessment.

Ultrasound of the placenta: a systematic approach. Part I: Imaging

Diagnostic ultrasound has been in use in clinical obstetrics for close to half-a-century. However, in the literature, examination of the placenta appears to be treated with less attention than the fetus or the pregnant uterus. This is somewhat unexpected, given the obvious major functions this organ performs during the entire pregnancy. Examination of the placenta plays a foremost role in the assessment of normal and abnormal pregnancies. A methodical sonographic evaluation of the placenta should include: location, visual estimation of the size (and, if appearing abnormal, measurement of thickness and/or volume), implantation, morphology, anatomy, as well as a search for anomalies, such as additional lobes and tumors. Additional assessment for multiple gestations consists of examining the intervening membranes (if present). The current review considers the various placental characteristics, as they can be evaluated by ultrasound, and the clinical significance of abnormalities of these features. Numerous and varied pathologies of the placenta can be detected by routine ultrasound. It is incumbent on the clinician performing obstetrical ultrasound to examine the placenta in details and in a methodical fashion because of the far reaching clinical significance and potentially avoidable severe consequences of many of these abnormalities.