Screening for morbidly adherent placenta in early pregnancy

Placenta accreta spectrum disorder complicating a second trimester miscarriage

Placenta accreta spectrum (PAS) disorder is a potentially life-threatening condition which rarely complicates second trimester miscarriages. This report describes a woman who was pregnant at 17 weeks with a history of previous caesarean section and uterine curettage. She presented with hypovolaemic shock following massive per-vaginal bleeding at home. A 180 g fetus was spontaneously aborted, but the placenta was retained in the uterus. After resuscitation, she underwent surgery, during which a morbidly adherent placenta was identified necessitating an emergency hysterectomy. Histopathological examination confirmed placenta accreta. This case highlights the risk of PAS complicating second trimester pregnancies and underscores the importance of early recognition and intervention to enhance maternal outcomes.

Placenta accreta spectrum in the second trimester: a clinical conundrum in procedural abortion care

Given the limitations in perioperative management strategies available at freestanding abortion clinics, abortion providers must commonly discern which patients are too complicated for procedural abortions at their center and must be referred for a hospital-based abortion. The need to transition from freestanding clinics to hospital-based abortion care can lead to delays in completing an abortion and significant social, economic, and psychological repercussions for the pregnant individual. One significant clinical problem that exemplifies the issue of who can be safely taken care of at a freestanding abortion clinic is when the placenta accreta spectrum is suspected. Placenta accreta spectrum is one of the major contributors to maternal morbidity and mortality in the United States, requiring coordinated multidisciplinary management to ensure the safest outcome for the pregnant individual. In this Clinical Opinion, we review the literature focused on identifying individuals at risk for placenta accreta spectrum >14+0 weeks gestation, delineate an algorithm to improve the frequency of timely referrals to hospital-based abortion providers, and propose next steps for future training goals and research on placenta accreta spectrum in the second trimester between complex family planning and maternal-fetal medicine subspecialists.

Early first-trimester transvaginal ultrasound screening for cesarean scar pregnancy in patients with previous cesarean delivery: analysis of the evidence

Obstetric hemorrhage is a leading cause of maternal morbidity and mortality. An important etiology of obstetric hemorrhage is placenta accreta spectrum. In the last 2 decades, there has been increased clinical experience of the devastating effect of undiagnosed, as well as late diagnosed, cases of cesarean scar pregnancy. There is a growing body of evidence suggesting that cesarean scar pregnancy is an early precursor of second- and third-trimester placenta accreta spectrum. As such, cesarean scar pregnancy should be diagnosed in the early first trimester. This early diagnosis could be achieved by introducing regimented sonographic screening in pregnancies of patients with previous cesarean delivery. This opinion article evaluates the scientific and clinical basis of whether cesarean scar pregnancy, with special focus on its early first-trimester discovery, complies with the accepted requirements of a screening test. Each of the 10 classical screening criteria of Wilson and Jungner were systematically applied to evaluate if the criteria were met by cesarean scar pregnancy, to analyze if it is possible and realistic to carry out screening in a population-wide fashion.

Prediction of pregnancy-related complications in women undergoing assisted reproduction, using machine learning methods

OBJECTIVE

To use machine learning methods to develop prediction models of pregnancy complications in women who conceived with assisted reproductive techniques (ART).

DESIGN

A nation-wide register-based cohort study with prospectively collected data.

SETTING

Swedish national registers and nationwide quality IVF register.

PATIENT(S)

all nulliparous women who achieved birth within the first 3 ART treatment cycles between 2008 and 2016 in Sweden.

INTERVENTION(S)

Characteristics before the use of ART, such as demographics and medical history, were considered potential predictors in the development of before treatment prediction models. ART treatment details were further included in after treatment prediction models.

MAIN OUTCOME MEASURE(S)

Potential diagnoses of preeclampsia, placental complications (previa, accreta, and abruption), and postpartum hemorrhage were identified using the International Classification of Diseases recorded in the Swedish Medical Birth and Patient registers, respectively. Multiple prediction model algorithms were performed and compared for each outcome and treatment cycle, including logistic regression, decision tree model, naïve Bayes classification, support vector machine, random forest, and gradient boosting. The performance of each model was assessed with C statistic, and nested cross-validation was used to aid model selection and hyperparameter tuning.

RESULT(S)

A total of 14,732 women gave birth after the first (N = 7,302), second (N = 4,688), or third (N = 2,742) ART cycle, representing birth rates of 24.1%, 23.8%, and 22.0%. Overall prediction performance did not vary much across the different methods used. In the first cycle, the before treatment prediction performance was at best 66%, 66%, and 60% for preeclampsia, placental complications, and postpartum hemorrhage, respectively. Inclusion of after treatment characteristics conferred slight improvement (approximately 1%-5%), as did prediction in later cycles (approximately 1%-5%). The top influential and consistent predictors included age, region of residence, infertility diagnosis, and type of embryo transfer (fresh or frozen) in the later (2nd and 3rd) cycles. Body mass index was a top predictor of preeclampsia and was also influential for placental complications but not for postpartum hemorrhage.

CONCLUSION(S)

The combined use of demographics, medical history, and ART treatment information was not enough to confidently predict serious pregnancy complications in women who conceived with ART. Future studies are needed to assess if additional longitudinal follow-up during pregnancy can improve the prediction to allow clinical protocol development.

Trimester-specific diagnostic accuracy of ultrasound for detection of placenta accreta spectrum: systematic review and meta-analysis

OBJECTIVE

To assess the diagnostic accuracy of ultrasound for detecting placenta accreta spectrum (PAS) during the first trimester of pregnancy and compare it with the accuracy of second- and third-trimester ultrasound examination in pregnancies at risk for PAS.

METHODS

PubMed, EMBASE and Web of Science databases were searched to identify relevant studies published from inception until 10 March 2023. Inclusion criteria were cohort, case-control or cross-sectional studies that evaluated the accuracy of ultrasound examination performed at < 14 weeks of gestation (first trimester) or ≥ 14 weeks of gestation (second/third trimester) for the diagnosis of PAS in pregnancies with clinical risk factors. The primary outcome was the diagnostic accuracy of sonography in detecting PAS in the first trimester, compared with the accuracy of ultrasound examination in the second and third trimesters. The secondary outcome was the diagnostic accuracy of each sonographic marker individually across the trimesters of pregnancy. The reference standard was PAS confirmed at pathological or surgical examination. The potential of ultrasound and different ultrasound signs to detect PAS was assessed by computing summary estimates of sensitivity, specificity, diagnostic odds ratio and positive and negative likelihood ratios.

RESULTS

A total of 37 studies, including 5764 pregnancies at risk of PAS, with 1348 cases of confirmed PAS, were included in our analysis. The meta-analysis demonstrated that ultrasound had a sensitivity of 86% (95% CI, 78-92%) and specificity of 63% (95% CI, 55-70%) during the first trimester, and a sensitivity of 88% (95% CI, 84-91%) and specificity of 92% (95% CI, 85-96%) during the second/third trimester. Regarding sonographic markers examined in the first trimester, lower uterine hypervascularity exhibited the highest sensitivity (97% (95% CI, 19-100%)), and uterovesical interface irregularity demonstrated the highest specificity (99% (95% CI, 96-100%)). In the second/third trimester, loss of clear zone had the highest sensitivity (80% (95% CI, 72-86%)), and uterovesical interface irregularity exhibited the highest specificity (99% (95% CI, 97-100%)).

CONCLUSIONS

First-trimester ultrasound examination has similar accuracy to second- and third-trimester ultrasound examinations for the diagnosis of PAS. Routine first-trimester ultrasound screening for patients at high risk of PAS may improve detection rates and allow earlier referral to tertiary care centers for pregnancy management. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Management of placenta accreta spectrum in low- and middle-income countries

Placenta accreta spectrum (PAS) can be associated massive intra- and post-operative hemorrhage which when not controlled can lead to maternal death. Important advances have occurred in understanding the pathophysiology and therapeutic options for this condition. The prevalence of PAS at birth is direct association with the cesarean delivery (CD) rate in the corresponding population and is increasing worldwide. Limited health infrastructure in low- and middle-income countries increases the morbidity and mortality of patients with PAS at birth. In many cases, obstetricians working in limited resources settings cannot follow some of the international guideline's recommendations and have to opt for low-cost management procedures. In this review, we describe the particularities of managing PAS care in low- and middle-income countries from of prenatal evaluation of patients at risk of PAS at birth, therapeutic options, and inter-institutional collaboration. We also propose a management protocol based on training of the local obstetric teams rather than on sophisticated technological resources that are almost never available in low-resource scenarios.

First-trimester screening for placenta accreta spectrum

In recent years, there has been a significant rise in cases of placenta accreta spectrum, a group of life-threatening placental disorders that can arise during childbirth. Early detection plays a crucial role in facilitating meticulous delivery planning, ultimately leading to a reduction in mortality and morbidity rates and improved overall outcomes. Although third-trimester ultrasound has traditionally been the primary method for prenatal screening for placenta accreta spectrum, it often falls short in identifying cases or diagnosis is too late for optimal delivery planning. Emerging evidence has highlighted the option of early detection of placenta accreta spectrum indicators during the first trimester of pregnancy. This comprehensive review delves into our current knowledge of sonographic assessment of the uterine cervicoisthmic complex in the first trimester, examining the location and appearance of cesarean scars and exploring first-trimester screening strategies, ultimately paving the way for improved maternal and neonatal outcomes.

Placenta acrreta spectrum-first trimester, 2D and 3D ultrasound, and magnetic resonance imaging findings

BACKGROUND

The term placenta accreta spectrum (PAS) is commonly used to describe abnormal trophoblastic invasion of the myometrium, serosa, or organs adjacent to the uterus. It is of great obstetric importance because of its high morbidity, risk of hemorrhage, admission to the intensive care unit, risk of hysterectomy, and high risk of iatrogenic pelvic lesions and even death. These risks are minimized when prenatal diagnosis is performed. Prenatal diagnosis of PAS is based on imaging findings suggestive of abnormal and pathologically adherent placentation, including placental lacunae (intraplacental sonolucent spaces), disruption of the bladder-uterine serosa interface, turbulent flow on color Doppler, and bridging vessels.

OBJECTIVE

In this article, we review the major prenatal imaging features of PAS using diagnostic modalities (first trimester, two-dimensional ultrasound, three-dimensional ultrasound, and magnetic resonance imaging) for the diagnosis of PAS.

Accuracy of ultrasound for the detection of placenta accreta spectrum in a universal screening population

OBJECTIVES

The current study aimed to determine the sensitivity and specificity of ultrasound for the diagnosis of placenta accreta spectrum (PAS) in a universal screening population and assesses the added value of magnetic resonance imaging (MRI).

METHODS

This retrospective analysis evaluated 5219 patients with singleton pregnancies who had a standardized ultrasound (US) examination in our unit and delivered at our institution between 2014 and 2019.

RESULTS

A total of 181 (3.5%) of 5219 (100%) patients had a suspicion or diagnosis of PAS with US. The accuracy of US in detecting placenta increta/percreta showed a sensitivity of 100%, specificity of 99.9%, positive predictive value of 82.4%, and a negative predictive value of 100%. The diagnosis of all forms of PAS showed a sensitivity of 25.8%, specificity of 99.8%, positive predictive value of 80.8%, and a negative predictive value of 97.7%. MRI was concordant with US in 11 of 14 (78.5%) cases of severe forms of PAS and in three of 15 (20.0%) cases with placenta accreta.

CONCLUSION

A standardized US evaluation can be applied in a universal screening setting for the diagnosis of severe forms of PAS. MRI is a complementary examination in severe forms of PAS but seems of limited value to discriminate placenta accreta from placenta increta/percreta.

Transcriptional Factor Forkhead Box D1 Upregulates Sirtuin3 by Activating the Wnt/β-Catenin Pathway to Alleviate HTR-8/Svneo Trophoblast Cell Dysfunction in Preeclampsia

The proliferation, invasion, migration and apoptosis of trophoblast cells in preeclampsia are closely related to the occurrence and development of preeclampsia. Transcription factors forkhead box D1 and Sirtuin3 are abnormally expressed in preeclampsia, and Sirtuin3 plays a regulatory role in cell proliferation, invasion and apoptosis in related diseases. However, the studies on forkhead box D1 and Sirtuin3 in preeclampsia and their specific mechanisms have not been reported so far. In this study, the expression of Sirtuin3 in Human chorionic trophoblast cells HTR-8/Svneo was inhibited by cell transfection, and then the effects of Sirtuin3 expression in interfering cells on cell invasion, migration and apoptosis were detected by MTT, TUNEL, Western blot, wound healing and Transwell techniques. Subsequently, the binding between forkhead box D1 and Sirtuin3 was predicted by JASPAR website and verified by luciferase assay and ChIP assay. Finally, cell invasion, migration and apoptosis were detected after overexpression of forkhead box D1 and interference with Sirtuin3, and the Wnt/β-catenin signaling pathway was detected to explore the mechanism. We found that interfering with Sirtuin3 induced apoptosis of HTR-8/Svneo cells and inhibited cell invasion and migration. Forkhead box D1 transcriptional activation of Sirtuin3 alleviated HTR-8/SVneo cell dysfunction through activation of the Wnt/β-catenin signaling pathway. Overall, transcriptional factor forkhead box D1 can upregulate Sirtuin3 by activating the Wnt/β-catenin pathway to alleviate HTR-8/Svneo trophoblast cell dysfunction in preeclampsia.

An update of diagnostic efficacy of ultrasound and magnetic resonance imaging in the diagnosis of clinically significant placenta accreta spectrum disorders

PURPOSE OF REVIEW

Systematic screening and diagnosis of placenta accreta spectrum disorder (PAS) either by ultrasound or magnetic resonance imaging (MRI) would allow referral of high-risk women to specialized multidisciplinary teams. We aimed to report recent findings regarding the diagnostic accuracy of ultrasound and magnetic resonance imaging in the diagnosis of PAS.

RECENT FINDINGS

Recent evidence from the literature shows that both ultrasound and MRI are good tests to identify PAS in high-risk populations. Ultrasound can also be used safely to guide management decisions, concentrating greater resources in patients with the higher risk of clinically significant PAS requiring complex peripartum management. Moreover, there are increasing data showing that routine contingent screening for PAS disorders based on the finding of a placenta implanted low in the uterine cavity and previous uterine surgery is effective in a public healthcare setting. A contingent screening strategy for PAS is feasible if placental location is routinely assessed during routine scans, and may even start from the first trimester of pregnancy.

SUMMARY

Ultrasound is an effective tool to screen pregnancies at high risk of PAS. In such pregnancies, ultrasound and MRI are effective imaging modalities for guiding management.

Prenatal detection of placenta previa and placenta accreta spectrum: Evaluation of the routine mid-pregnancy obstetric ultrasound screening between 2013 and 2017

OBJECTIVE

To examine the detection rate of placenta previa and placenta accreta spectrum (PAS) by routine mid-pregnancy obstetric ultrasound and to estimate risk factors and prevalence within this cohort.

METHODS

This was an observational cohort study with prospectively collected data. Women attending routine mid-pregnancy obstetric ultrasound at the Sahlgrenska University Hospital with a suspected cup-shaped placenta (cohort 1, n = 339) and women diagnosed with placenta previa or PAS (cohort 2, n = 227) were analyzed according to detection rate, risk factors, and prevalence.

RESULTS

The detection rates of placenta previa and PAS were 49% (98) and 25% (14), respectively. However, 216 (99%) women with placenta previa were diagnosed prenatally, as were 14 (50%) women with PAS. In vitro fertilization was identified as the strongest independent risk factor for placenta previa (odds ratio 6.96; 95% confidence interval 4.77-10.16, P < 0.001). Risk factors were present for all women with PAS. The prevalence of placenta previa was 44/10 000 deliveries, and for PAS, 5.6/10 000 deliveries.

CONCLUSION

The existing routine mid-pregnancy obstetric ultrasound screening showed low detection rate for placenta previa and PAS. Adding risk factors could improve the detection rate.

Caesarean Scar Pregnancy: A Case Report and a Literature Review

Background and Objectives: Caesarean scar pregnancy (CSP) refers to placental implantation on or in the scar of a previous caesarean section and represents a potentially life-threatening condition. CSP is considered a diagnostic challenge in obstetrics, with the diagnosis relying mainly on transvaginal ultrasound (TVS) and the management depending upon case presentation and available healthcare infrastructures. Case Presentation: We present a case of 34-year-old G3P2 with a history of two-previous caesarean sections referred to the outpatient gynaecology clinic of our Department at the 7th week (7/40) of gestation with abnormal early pregnancy TVS findings, illustrating the gestational sac attached to the caesarean scar and a foetal pole with evidence of foetal cardiac activity. We discuss the outcome of an alternative combined medical and surgical approach we followed as well as an updated review of the current literature. Conclusions: The ideal management of CSP requires tertiary centers, equipment availability and experienced healthcare professionals capable of dealing with any possible complication, as well as individualized treatment based on each case presentation.

First-trimester ultrasound diagnostic features of placenta accreta spectrum in low-implantation pregnancy

OBJECTIVE

Low-implantation pregnancy (LIP) is an important marker for the diagnosis of placenta accreta spectrum (PAS) in the first trimester. Many grayscale and color Doppler ultrasound markers of PAS have been defined in the second and third trimesters of pregnancy, but have not been studied in the first trimester. The aim of this study was to determine whether PAS sonographic markers could be used in the first trimester to differentiate patients with LIP who develop PAS from those who do not.

METHODS

This was a retrospective case-control study of women who delivered at our institution between 2009 and 2019. Cases were women with PAS who delivered by Cesarean hysterectomy and who had undergone first-trimester ultrasound demonstrating LIP. Controls were women with persistent placenta previa without PAS who delivered by Cesarean section without postpartum hemorrhage and who had undergone first-trimester ultrasound demonstrating LIP. Sonographic images were reviewed by an investigator blinded to pregnancy outcome and ultrasound reports. Images were reviewed for presence of abnormal uteroplacental interface, increased lower uterine segment hypervascularity and placental lacunae, with or without swirling on grayscale or color Doppler ultrasound.

RESULTS

Following review of the electronic health records, 21 cases and 46 controls met the inclusion criteria. Placental lacunae were present in 18/21 (85.7%) cases and 7/46 (15.2%) controls (odds ratio (OR), 33.4; 95% CI, 7.7-144.4; P < 0.001). The number of lacunae was significantly higher in cases compared with controls, with a median of five lacunae present in cases compared with a median of one lacuna in controls (P < 0.001). The median size of the lacunae was also significantly larger in cases compared with controls, measuring 10.03 (interquartile range (IQR), 7.3-12.05) mm and 4.15 (IQR, 4.05-5.05) mm, respectively (P = 0.001). Lacunae swirling on grayscale or color Doppler ultrasound was noted only in PAS cases, with 10/12 (83.3%) having swirling on grayscale ultrasound and 12/12 (100%) having swirling on color Doppler (P < 0.001). Presence of an abnormal uteroplacental interface was also observed only in PAS cases, at a rate of 17/20 (85.0%) (P < 0.001). Lower uterine segment (uterovesical, subplacental and/or intraplacental) hypervascularity was present in 14/14 (100%) cases and only 1/12 (8.3%) controls (P < 0.001).

CONCLUSION

In women at risk of PAS, ultrasound markers of PAS can and should be assessed as early as in the first trimester. The use of a first-trimester prenatal ultrasound screening protocol and standardized approach to ultrasound examination in at-risk mothers may help increase detection of PAS and enable planning for optimal management of affected pregnancies. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

New insights into the etiopathology of placenta accreta spectrum

Placenta accreta has been described as a spectrum of abnormal attachment of villous tissue to the uterine wall, ranging from superficial attachment to the inner myometrium without interposing decidua to transmural invasion through the entire uterine wall and beyond. These descriptions have prevailed for more than 50 years and form the basis for the diagnosis and grading of accreta placentation. Accreta placentation is essentially the consequence of uterine remodeling after surgery, primarily after cesarean delivery. Large cesarean scar defects in the lower uterine segment are associated with failure of normal decidualization and loss of the subdecidual myometrium. These changes allow the placental anchoring villi to implant, and extravillous trophoblast cells to migrate, close to the serosal surface of the uterus. These microscopic features are central to the misconception that the accreta placental villous tissue is excessively invasive and have led to much confusion and heterogeneity in clinical data. Progressive recruitment of large arteries in the uterine wall, that is, helicine, arcuate, and/or radial arteries, results in high-velocity maternal blood entering the intervillous space from the first trimester of pregnancy and subsequent formation of placental lacunae. Recently, guided sampling of accreta areas at delivery has enabled accurate correlation of prenatal imaging data with intraoperative features and histopathologic findings. In more than 70% of samples, there were thick fibrinoid depositions between the tip of most anchoring villi and the underlying uterine wall and around all deeply implanted villi. The distortion of the uteroplacental interface by these dense depositions and the loss of the normal plane of separation are the main factors leading to abnormal placental attachment. These data challenged the classical concept that placenta accreta is simply owing to villous tissue sitting atop the superficial myometrium without interposed decidua. Moreover, there is no evidence in accreta placentation that the extravillous trophoblast is abnormally invasive or that villous tissue can cross the uterine serosa into the pelvis. It is the size of the scar defect, the amount of placental tissue developing inside the scar, and the residual myometrial thickness in the scar area that determine the distance between the placental basal plate and the uterine serosa and thus the risk of accreta placentation.

Development of the utero-placental circulation in cesarean scar pregnancies: a case-control study

BACKGROUND

Cesarean scar pregnancies carry a high risk of pregnancy complications including placenta previa with antepartum hemorrhage, placenta accreta spectrum, and uterine rupture.

OBJECTIVE

To evaluate the development of utero-placental circulation in the first half of pregnancy in ongoing cesarean scar pregnancies and compare it with pregnancies implanted in the lower uterine segment above a previous cesarean delivery scar with no evidence of placenta accreta spectrum at delivery STUDY DESIGN: This was a retrospective case-control study conducted in 2 tertiary referral centers. The study group included 27 women who were diagnosed with a live cesarean scar pregnancy in the first trimester of pregnancy and who elected to conservative management. The control group included 27 women diagnosed with an anterior low-lying placenta or placenta previa at 19 to 22 weeks of gestation who had first and early second trimester ultrasound examinations. In both groups, the first ultrasound examination was carried out at 6 to 10 weeks to establish the pregnancy location, viability, and to confirm the gestational age. The utero-placental and intraplacental vasculatures were examined using color Doppler imaging and were described semiquantitatively using a score of 1 to 4. The remaining myometrial thickness was recorded in the study group, whereas the ultrasound features of a previous cesarean delivery scar including the presence of a niche were noted in the controls. Both the cesarean scar pregnancies and the controls had ultrasound examinations at 11 to 14 and 19 to 22 weeks of gestation.

RESULTS

The mean color Doppler imaging vascularity score in the ultrasound examination at 6 to 10 weeks was significantly (P<.001) higher in the cesarean scar pregnancy group than in the controls. High vascularity scores of 3 and 4 were recorded in 20 of 27 (74%) cases of the cesarean scar pregnancy group. There was no vascularity score of 4, and only 3 of 27 (11%) controls had a vascularity score of 3. In 15 of the 27 (55.6%) cesarean scar pregnancies, the residual myometrial thickness was <2 mm. In the ultrasound examination at 11 to 14 weeks, there was no significant difference between the groups in the number of cases with an increased subplacental vascularity. However, 12 cesarean scar pregnancies (44%) presented with 1 or more placental lacunae whereas there was no case with lacunae in the controls. Of the 18 cesarean scar pregnancies that progressed into the third trimester, 10 of them were diagnosed with placenta previa accreta at birth, including 4 creta and 6 increta. In the 19 to 22 weeks ultrasound examination, 8 of the 10 placenta accreta spectrum patients presented with subplacental hypervascularity, out of which 6 showed placental lacunae.

CONCLUSION

The vascular changes in the utero-placental and intervillous circulations in cesarean scar pregnancies are due to the loss of the normal uterine structure in the scar area and the development of placental tissue in proximity of large diameter arteries of the outer uterine wall. The intensity of these vascular changes, the development of placenta accreta spectrum, and the risk of uterine rupture are probably related to the residual myometrial thickness of the scar defect at the start of pregnancy. A better understanding of the pathophysiology of the utero-placental vascular changes associated with cesarean scar pregnancies should help in identifying those cases that may develop major complications. It will contribute to providing counseling for women about the risks associated with different management strategies.

First Trimester Prediction of Adverse Pregnancy Outcomes—Identifying Pregnancies at Risk from as Early as 11–13 Weeks

There is consistent evidence that many of the pregnancy complications that occur late in the second and third trimester can be predicted from an integrated 11–13 weeks visit, where a maternal and fetal assessment are comprehensively performed. The traditional aims of the 11–13 weeks visit have been: establishing fetal viability, chorionicity and dating of the pregnancy, and performing the combined screening test for common chromosomal abnormalities. Recent studies have shown that the first trimester provides important information that may help to predict pregnancy complications, such as preeclampsia and fetal growth restriction, stillbirth, preterm birth, gestational diabetes mellitus and placenta accreta spectrum disorder. The aim of this manuscript is to review the methods available to identify pregnancies at risk for adverse outcomes after screening at 11–13 weeks. Effective screening in the first trimester improves pregnancy outcomes by allowing specific interventions such as administering aspirin and directing patients to specialist clinics for regular monitoring.

Lower uterine segment scar assessment at 11-14 weeks' gestation to screen for placenta accreta spectrum in women with prior Cesarean delivery

OBJECTIVES

To validate prospectively transvaginal ultrasound assessment of the lower uterine segment (LUS) scar at the time of first-trimester screening in women with previous Cesarean section (CS) and to determine its feasibility and accuracy in stratifying women according to the risk for placenta accreta spectrum (PAS) disorder.

METHODS

Women with a history of CS were recruited between 11 + 0 and 13 + 6 weeks' gestation and underwent LUS scar assessment using transvaginal ultrasound. A standardized midsagittal plane, which included the cervicoisthmic canal (CIC), the uterine scar and the placental site, was obtained. The scar was described in terms of its size (narrow or dehiscent) and its location in relation to the CIC (within or above), with each LUS scar classified into one of four groups based on these features. Placental location was assessed and classified as high- or low-lying. Women were stratified according to the risk of PAS, based on the relationship between the scar location and placental site. Women were considered high risk when the scar was above the CIC and the placenta was low-lying (i.e. when the placenta was overlying an exposed scar) and low risk when the scar was within the CIC and/or the placenta was high. High-risk patients were followed up at 20 weeks and 28-30 weeks for the development of PAS. Maternal demographics, detailed obstetric history and obstetric outcome were collected.

RESULTS

First-trimester transvaginal ultrasound was offered to 535 women with prior CS during the study period. A LUS scar was visualized in 79.9% (401/502) of those who agreed to undergo the examination. At this scan, the LUS scar was above the CIC in 9.0% (36/401) of women, but only 5.7% (23/401) additionally had a low-lying placenta overlying the scar. Of these 23 high-risk women, two were found to have PAS on the mid-trimester screening scan and one was noted to have placental adherence during evacuation following mid-trimester termination of pregnancy. On the first-trimester scan, 94.3% (378/401) of women were at low risk of PAS. This screening protocol yielded a positive likelihood ratio of 21.33 (95% CI, 13.02-34.96), sensitivity of 100% (95% CI, 29.24-100%), specificity of 95.31% (95% CI, 92.39-97.35%), positive predictive value of 16.7% (95% CI, 5.8-39.2%) and negative predictive value of 100% (95% CI, 98.4-100%). On multivariable regression analysis performed to identify confounding variables associated with a LUS scar above the CIC, only maternal body mass index ≥ 30 kg/m² was significant (odds ratio (OR), 2.42 (95% CI, 1.04-5.39); P = 0.03). Although there was a trend towards an increased risk of a LUS scar above the CIC in women with prior elective prelabor CS (OR, 1.72 (95% CI, 0.80-3.68)), this association did not reach statistical significance.

CONCLUSIONS

Routine transvaginal ultrasound assessment of the location of the LUS scar and placenta at the time of first-trimester screening between 11 + 0 and 13 + 6 weeks' gestation in women with prior CS is a feasible and effective tool to identify those at risk of subsequent development of PAS disorder. A finding of placental implantation over an exposed LUS scar seems to be cardinal in predicting the risk of PAS disorder in women with prior CS, with an excellent negative predictive value. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Transvaginal Color Mapping Ultrasound in the First Trimester Predicts Placenta Accreta Spectrum: A Retrospective Cohort Study

OBJECTIVES

Ultrasound (US) prediction of placenta accreta spectrum (PAS) in the first trimester may be aided by postprocessing mechanisms employing color pixel quantification near the bladder-uterine serosal interface. Our objective was to create a postprocessing algorithm of color images to identify findings associated with PAS and compare quantification to sonologist impression in prospectively obtained cine US images.

METHODS

Transverse transvaginal (TV) US color cines obtained in the first trimester as part of a prospective study were reviewed. Investigators blinded to clinical outcomes reviewed anonymized cines that were archived and labeled the bladder-uterine serosal interface. Color pixels within 2 cm of the defined bladder-uterine serosal interface were ascertained using a Python-based plugin in the Horos open-source DICOM viewer. A sonologist classified the findings as suspicious for invasion, indeterminate, or normal. Statistical analysis was performed using Wilcoxon rank-sum test, Cochran-Armitage trend test, and calculation of receiver-operating characteristic (ROC) curves.

RESULTS

Fifty-four studies met inclusion criteria. Of those, six (11%) required hysterectomy with pathologic confirmation of PAS. Women requiring hysterectomy had a significantly higher color Doppler pixel area than those not requiring hysterectomy (P = .0205). A significant trend was identified in the sonologist impression of invasion (P = .0003). ROC's comparing sonologist impression to Doppler color imaging areas were comparable (P = .054).

CONCLUSIONS

Color Doppler mapping in the first trimester showed an increase in color pixel area near the bladder-uterine serosal interface in women requiring cesarean hysterectomy with histologically confirmed PAS at time of delivery, compared to women without hysterectomy or pathologic evidence of PAS.

Placenta Accreta Spectrum Disorder in a Patient with Six Previous Caesarean Deliveries: Step by Step Management

The definition placenta accreta spectrum disorders (PAS) introduced by FIGO (International Federation of Gynaecology and Obstetrics) indicates an abnormal, pathological adherence or invasion of the placenta. The growing worldwide incidence of this pathological entity, and the possible serious correlated surgical risks, has caused a significant increase in attention among the scientific community. Previous caesarean delivery and presence of placenta previa are the main risk factors for the onset of PAS. Here, we present the intriguing case of a 39-year-old woman, at the 33rd week of gestation, with six previous caesarean sections and with a diagnosis of placenta previa accreta. At our referral center for PAS disorders, we successfully managed this difficult case with the help of a multidisciplinary skilled team.

Placenta increta presenting with threatened miscarriage during the first trimester in rhesus-negative mother: a case report

BACKGROUND

Placenta accreta is known to be associated with significant maternal morbidity and mortality-primarily due to intractable bleeding during abortion or delivery at any level of gestation. The complications could be reduced if placenta accreta is suspected in a patient with a history of previous cesarean delivery and the gestational sac/placenta is located at the lower part of the uterus. Then, a proper management plan can be instituted, and complications can be reduced. The diagnosis of placenta accreta in the first trimester of pregnancy is considered uncommon.

CASE PRESENTATION

A 34-year-old Malay, gravida 4, para 3, rhesus-negative woman was referred from a private hospital at 13 weeks owing to accreta suspicion for further management. She has a history of three previous lower-segment cesarean sections. She also had per vaginal bleeding in the early first trimester, which is considered to indicate threatened miscarriage. Transabdominal ultrasound revealed features consistent with placenta accreta spectrum. She was counseled for open laparotomy and hysterectomy because of potential major complication if she continued with the pregnancy. Histopathological examination revealed placenta increta.

CONCLUSION

A high index of suspicion of placenta previa accreta must be in practice in a patient with a history of previous cesarean deliveries and low-lying placenta upon ultrasound examination during early gestation.

Diagnosis and Management of Cesarean Scar Pregnancy and Placenta Accreta Spectrum: Case Series and Review of the Literature

With an increased cesarean delivery rate, the incidence of abnormal placentation is steadily rising, and it is estimated to be around 1.7 per 1000 pregnancies for cesarean scar pregnancy and 1 per 500 pregnancies for placenta accreta spectrum disorder. Current evidence considers cesarean scar pregnancy and placenta accreta spectrum as being the same condition, with different aspects, of the same spectrum, having higher risks with advancing gestation. We present 7 cases, diagnosed and managed in our hospital, at different gestational ages. Early diagnosis is essential for appropriate counseling and subsequent management, and an ultrasound examination is the reference standard for diagnosis. Screening for an abnormally implanted placenta in the first trimester of pregnancy might improve the perinatal outcome and reduce maternal morbidity and mortality.

Routine ultrasound for fetal assessment before 24 weeks' gestation

BACKGROUND

Ultrasound examination of pregnancy before 24 weeks gestation may lead to more accurate dating and earlier diagnosis of pathology, but may also give false reassurance. It can be used to monitor development or diagnose conditions of an unborn baby. This review compares the effect of routine or universal, ultrasound examination, performed before 24 completed weeks' gestation, with selective or no ultrasound examination.  OBJECTIVES: To assess the effect of routine pregnancy ultrasound before 24 weeks as part of a screening programme, compared to selective ultrasound or no ultrasound, on the early diagnosis of abnormal pregnancy location, termination for fetal congenital abnormality, multiple pregnancy, maternal outcomes and later fetal compromise. To assess the effect of first trimester (before 14 weeks) and second trimester (14 to 24 weeks) ultrasound, separately.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, and the World Health Organization's International Clinical Trials Registry Platform (ICTRP) on 11 August 2020. We also examined the reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), quasi-RCTs, cluster-RCTs and RCTs published in abstract form. We included all trials with pregnant women who had routine or revealed ultrasound versus selective ultrasound, no ultrasound, or concealed ultrasound, before 24 weeks' gestation. All eligible studies were screened for scientific integrity and trustworthiness.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for eligibility and risk of bias, extracted data and checked extracted data for accuracy. Two review authors independently used the GRADE approach to assess the certainty of evidence for each outcome MAIN RESULTS: Our review included data from 13 RCTs including 85,265 women. The review included four comparisons. Four trials were assessed to be at low risk of bias for both sequence generation and allocation concealment and two as high risk. The nature of the intervention made it impossible to blind women and staff providing care to treatment allocation.  Sample attrition was low in the majority of trials and outcome data were available for most women. Many trials were conducted before it was customary for trials to be registered and protocols published. First trimester routine versus selective ultrasound: four studies, 1791 women, from Australia, Canada, the United Kingdom (UK) and the United States (US). First trimester scans probably reduce short-term maternal anxiety about pregnancy (risk ratio (RR) 0.80, 95% confidence interval (CI) 0.65 to 0.99; moderate-certainty evidence). We do not have information on whether the reduction was sustained.  The evidence is very uncertain about the effect of first trimester scans on perinatal loss (RR 0.97, 95% CI 0.55 to 1.73; 648 participants; one study; low-certainty evidence) or induction of labour for post-maturity (RR 0.83, 95% CI 0.50 to 1.37; 1474 participants; three studies; low-certainty evidence). The effect of routine first trimester ultrasound on birth before 34 weeks or termination of pregnancy for fetal abnormality was not reported. Second trimester routine versus selective ultrasound: seven studies, 36,053 women, from Finland, Norway, South Africa, Sweden and the US. Second trimester scans probably make little difference to perinatal loss (RR 0.98, 95% CI 0.81 to 1.20; 17,918 participants, three studies; moderate-certainty evidence) or intrauterine fetal death (RR 0.97, 95% CI 0.66 to 1.42; 29,584 participants, three studies; low-certainty evidence). Second trimester scans may reduce induction of labour for post-maturity (RR 0.48, 95% CI 0.31 to 0.73; 24,174 participants, six studies; low-certainty evidence), presumably by more accurate dating. Routine second trimester ultrasound may improve detection of multiple pregnancy (RR 0.05, 95% CI 0.02 to 0.16; 274 participants, five studies; low-certainty evidence). Routine second trimester ultrasound may increase detection of major fetal abnormality before 24 weeks (RR 3.45, 95% CI 1.67 to 7.12; 387 participants, two studies; low-certainty evidence) and probably increases the number of women terminating pregnancy for major anomaly (RR 2.36, 95% CI 1.13 to 4.93; 26,893 participants, four studies; moderate-certainty evidence). Long-term follow-up of children exposed to scans before birth did not indicate harm to children's physical or intellectual development (RR 0.77, 95% CI 0.44 to 1.34; 603 participants, one study; low-certainty evidence). The effect of routine second trimester ultrasound on birth before 34 weeks or maternal anxiety was not reported. Standard care plus two ultrasounds and referral for complications versus standard care: one cluster-RCT, 47,431 women, from Democratic Republic of Congo, Guatemala, Kenya, Pakistan and Zambia. This trial included a co-intervention, training of healthcare workers and referral for complications and was, therefore, assessed separately. Standard pregnancy care plus two scans, and training and referral for complications, versus standard care probably makes little difference to whether women with complications give birth in a risk appropriate setting with facilities for caesarean section (RR 1.03, 95% CI 0.89 to 1.19; 11,680 participants; moderate-certainty evidence).  The intervention also probably makes little to no difference to low birthweight (< 2500 g) (RR 1.01, 95% CI 0.90 to 1.13; 47,312 participants; moderate-certainty evidence). The evidence is very uncertain about whether the community intervention (including ultrasound) makes any difference to maternal mortality (RR 0.92, 95% CI 0.55 to 1.55; 46,768 participants; low-certainty evidence). Revealed ultrasound results (communicated to both patient and doctor) versus concealed ultrasound results (blinded to both patient and doctor at any time before 24 weeks): one study, 1095 women, from the UK. The evidence was very uncertain for all results relating to revealed versus concealed ultrasound scan (very low-certainty evidence).

AUTHORS' CONCLUSIONS

Early scans probably reduce short term maternal anxiety.  Later scans may reduce labour induction for post-maturity. They may improve detection of major fetal abnormalities and increase the number of women who choose termination of pregnancy for this reason. They may also reduce the number of undetected twin pregnancies. All these findings accord with observational data.  Neither type of scan appears to alter other important maternal or fetal outcomes, but our review may underestimate the effect in modern practice because trials were mostly  from relatively early in the development of the technology, and many control participants also had scans. The trials were also underpowered to show an effect on other important maternal or fetal outcomes.

Committee Opinion No. 418: The Complete 11-14 Week Prenatal Sonographic Examination

OBJECTIVE

Sonography during the first trimester provides an opportunity to assess a pregnancy in its early stage. This document provides an opinion about the implementation and content of prenatal sonographic examinations at 11-14 weeks gestation in Canada.

TARGET POPULATION

Pregnant women at 11-14 weeks gestation.

BENEFITS, HARMS, AND COSTS

The 11-14 week prenatal sonographic examination can provide important information that may contribute to pregnancy management. It can be used to confirm viability, establish gestational age, determine the number of fetuses, assess the adnexa/ovaries, and, in a multiple pregnancy, assess chorionicity and amnionicity. Scanning also offers an opportunity to detect fetal abnormalities and perform aneuploidy screening by measuring the nuchal translucency thickness. It may be valuable in screening for preeclampsia and other obstetrical disorders (by combining uterine artery Doppler scanning with other bio-clinical markers) and for invasive placentation. There are no physical harms to mother or fetus from offering a routine 11-14 week prenatal sonographic examination, and there are no extra costs for patients.

EVIDENCE

Articles related to routine 11-14 week prenatal sonography were identified in a search of EMBASE and MEDLINE using the search terms first trimester ultrasound, nuchal translucency, and 11-14 week ultrasound. The search included all articles published on the topic until May 2019. Abstracts were reviewed by one author, and articles deemed relevant were then reviewed in full to determine whether to include them in the study. Articles that were not in English and articles that did not pertain to 11-14 week prenatal sonography were excluded.

INTENDED AUDIENCE

This document is intended for sonographers, midwives, family physicians, obstetricians, and maternal-fetal medicine specialists.

Recurrent severe placenta increta at 8 weeks of gestation in a twin pregnancy following uterus-conserving surgery for prior placenta accreta spectrum disorder

OBJECTIVE

We describe herein our experience of employing a hysterectomy and prophylactic internal iliac artery balloon occlusion (IIABO) strategy for the management of recurrent severe placenta increta at 8 weeks in a twin pregnancy following uterus-conserving surgery for prior placenta accreta spectrum (PAS) disorder.

CASE REPORT

A 40-year-old woman with a history of uterus-conserving surgery for PAS disorder underwent transvaginal ultrasound evaluation at 8 weeks of pregnancy, which showed a dichorionic/diamniotic pregnancy with viable embryos of a crown-rump length of 1.65 cm and 2.03 cm, respectively. Many irregularly-shaped grade 3+ lacunae were observed, and color Doppler imaging revealed diffuse intraplacental and perihypervascularity. A total abdominal hysterectomy was performed at 10 weeks, with an estimated blood loss of 1275 mL. Placenta increta was confirmed by histopathologic examination.

CONCLUSION

The high rate of recurrence of PAS disorder in a subsequent pregnancy should be discussed following an antenatal diagnosis of PAS disorder with patients who may be considering uterine conservation in order to retain the option of a future pregnancy.

Successful treatment of placenta accreta spectrum disorder using management strategy of serial uterine artery embolization combined with standard weekly and a 8-day methotrexate/folinic acid regimens at 7 weeks of gestation

OBJECTIVE

We describe our experience with serial uterine artery embolization (UAE) combined with standard weekly methotrexate and a eight-day methotrexate/folinic acid (MTX/FA) treatment regimen in the management of placenta accreta spectrum (PAS) disorder at 7 weeks of gestation.

CASE REPORT

A 38-year-old woman, gravida 2 para 0, with a history of myomectomy, was referred for ultrasound (US) evaluation due to suspected cervico-isthmic pregnancy. Transvaginal US image showed a viable embryo with a disproportionately bigger placenta encircling the fetus and completely covering the internal os of the cervix at 7 weeks of gestation. Color Doppler imaging revealed diffuse intraplacental and periplacental vascularity. Patient chose to terminate the pregnancy but attempted to preserve the uterus for future fertility following counseling. Serial UAE procedures were performed using Gelfoam and metallic microcoils. Two courses of a standard weekly MTX and a eight-day MTX/FA treatment regimen were administered to accelerate placental regression. The beta-hCG gradually decreased to a normal level, and an ultimate resolution of the PAS disorder was observed at 110 days after treatment.

CONCLUSION

Early diagnosis of the PAS disorder could result in better obstetric outcome through earlier intervention using serial UAE combined with standard weekly and a eight day MTX//FA regimen in the first trimester of pregnancy.

Multiscale and multimodal imaging of utero-placental anatomy and function in pregnancy

Placental structures at the nano-, micro-, and macro scale each play important roles in contributing to its function. As such, quantifying the dynamic way in which placental structure evolves during pregnancy is critical to both clinical diagnosis of pregnancy disorders, and mechanistic understanding of their pathophysiology. Imaging the placenta, both exvivo and invivo, can provide a wealth of structural and/or functional information. This review outlines how imaging across modalities and spatial scales can ultimately come together to improve our understanding of normal and pathological pregnancies. We discuss how imaging technologies are evolving to provide new insights into placental physiology across disciplines, and how advanced computational algorithms can be used alongside state-of-the-art imaging to obtain a holistic view of placental structure and its associated functions to improve our understanding of placental function in health and disease.

Pregnancy-Related Hysterectomy for Peripartum Hemorrhage: A Literature Narrative Review of the Diagnosis, Management, and Techniques

Postpartum hemorrhage is a life-threatening situation, in which hysterectomy can be performed to prevent maternal death. However, it is associated with high rates of maternal morbidity and mortality and permanent infertility. The incidence of pregnancy-related hysterectomy varies across countries, but its main indications are the following: uterine atony and placenta spectrum (PAS) disorders. PAS disorder prevalence is rising during the last years, mainly due to the increased number of cesarean sections. As a result, obstetricians should be aware of the difficulties of this emergent condition and improve its accurate antenatal diagnosis rates, as well as its modern management strategies. Of course, special skills are required during a pregnancy-related hysterectomy, so these patients should be referred to centers of excellence in antenatal care, where a multidisciplinary team approach is followed. This study is a narrative review of the literature of the last 5 years (PubMed, Cochrane) regarding postpartum hemorrhage to offer obstetricians up-to-date knowledge on this pregnancy-related life-threatening issue. However, there is a lack of available high-quality data, because most published papers are retrospective case series or observational cohorts.

Rethinking Prenatal Screening for Anomalies of Placental and Umbilical Cord Implantation

The most common anomalies of implantation of the placenta and umbilical cord include placenta previa, placenta accreta spectrum, and vasa previa, and are associated with considerable perinatal and maternal morbidity and mortality. There is moderate quality evidence that prenatal diagnosis of these conditions improves perinatal outcomes and the performance of ultrasound imaging in diagnosing them is considered excellent. The epidemiology of placenta previa is well known, and it is standard clinical practice to assess placental location at the routine screening second-trimester detailed fetal anatomy ultrasound examination. In contrast, the prevalence of placenta accreta spectrum and vasa previa in the general population is more difficult to evaluate because detailed confirmatory histopathologic data are not available in most studies. The sensitivity and specificity of ultrasonography for the diagnosis of these anomalies is also difficult to assess. Recent epidemiologic studies show an increase in the incidence of placental and umbilical cord implantation anomalies, which may be the result of increased use of assisted reproductive technology and cesarean delivery. There is good evidence to support targeted standardized protocols for women at high risk and that screening and diagnosing placenta accreta spectrum and vasa previa should be integrated into obstetric ultrasound training programs.

Effectiveness of contingent screening for placenta accreta spectrum disorders based on persistent low-lying placenta and previous uterine surgery

OBJECTIVES

Maternal mortality related to placenta accreta spectrum (PAS) disorders remains substantial when diagnosed unexpectedly at delivery. The aim of this study was to evaluate the effectiveness of a routine contingent ultrasound screening program for PAS.

METHODS

This was a retrospective study of data obtained between 2009 and 2019, involving two groups: a screening cohort of unselected women attending for routine mid-trimester ultrasound assessment and a diagnostic cohort consisting of women referred to the PAS diagnostic service with a suspected diagnosis of PAS. In the screening cohort, women with a low-lying placenta at the mid-trimester assessment were followed up in the third trimester, and those with a persistent low-lying placenta (i.e. placenta previa) and previous uterine surgery were referred to the PAS diagnostic service. Ultrasound assessment by the PAS diagnostic service consisted of two-dimensional grayscale and color Doppler ultrasonography, and women with a diagnosis of PAS were usually managed with conservative myometrial resection. The final diagnosis of PAS was based on a combination of intraoperative clinical findings and histopathological examination of the surgical specimen.

RESULTS

In total, 57 179 women underwent routine mid-trimester fetal anatomy assessment, of whom 220 (0.4%) had a third-trimester diagnosis of placenta previa. Seventy-five of these women were referred to the PAS diagnostic service because of a history of uterine surgery, and 21 of 22 cases of PAS were diagnosed correctly (sensitivity, 95.45% (95% CI, 77.16-99.88%) and specificity, 100% (95% CI, 99.07-100%)). Univariate analysis demonstrated that parity ≥ 2 (odds ratio (OR), 35.50 (95% CI, 6.90-649.00)), two or more previous Cesarean sections (OR, 94.20 (95% CI, 22.00-656.00)) and placenta previa (OR, 20.50 (95% CI, 4.22-369.00)) were the strongest risk factors for PAS. In the diagnostic cohort, there were 173 referrals, with one false-positive and three false-negative diagnoses, resulting in a sensitivity of 96.63% (95% CI, 90.46-99.30%) and a specificity of 98.81% (95% CI, 93.54-99.97%).

CONCLUSIONS

A contingent screening strategy for PAS is both feasible and effective in a routine healthcare setting. When linked to a PAS diagnostic and surgical management service, adoption of such a screening strategy has the potential to reduce the maternal morbidity and mortality associated with this condition. However, larger prospective studies are necessary before implementing this screening strategy into routine clinical practice. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Special Report of the Society for Maternal-Fetal Medicine Placenta Accreta Spectrum Ultrasound Marker Task Force: Consensus on definition of markers and approach to the ultrasound examination in pregnancies at risk for placenta accreta spectrum

Placenta accreta spectrum includes the full range of abnormal placental attachment to the uterus or other structures, encompassing placenta accreta, placenta increta, placenta percreta, morbidly adherent placenta, and invasive placentation. The incidence of placenta accreta spectrum has increased in recent years, largely driven by increasing rates of cesarean delivery. Prenatal detection of placenta accreta spectrum is primarily made by ultrasound and is important to reduce maternal morbidity associated with the condition. Despite a large body of research on various placenta accreta spectrum ultrasound markers and their screening performance, inconsistencies in the literature persist. In response to the need for standardizing the definitions of placenta accreta spectrum markers and the approach to the ultrasound examination, the Society for Maternal-Fetal Medicine convened a task force with representatives from the American Institute of Ultrasound in Medicine, the American College of Obstetricians and Gynecologists, the American College of Radiology, the International Society of Ultrasound in Obstetrics and Gynecology, the Society for Radiologists in Ultrasound, the American Registry for Diagnostic Medical Sonography, and the Gottesfeld-Hohler Memorial Ultrasound Foundation. The goals of the task force were to assess placenta accreta spectrum sonographic markers on the basis of available data and expert consensus, provide a standardized approach to the prenatal ultrasound evaluation of the uterus and placenta in pregnancies at risk of placenta accreta spectrum, and identify research gaps in the field. This manuscript provides information on the Placenta Accreta Spectrum Task Force process and findings.

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.

Prospective First-Trimester Ultrasound Imaging of Low Implantation and Placenta Accreta Spectrum

OBJECTIVES

To prospectively evaluate low implantation of the gestational sac and other first-trimester ultrasound (US) parameters for prediction of placenta accreta spectrum (PAS).

METHODS

Women with a diagnosis of low implantation on clinically indicated first-trimester US underwent a transvaginal US examination at 10 to 13 weeks' gestation to assess the trophoblast location, anechoic areas, bridging vessels, and smallest myometrial thickness (SMT). The placental location was evaluated in the second trimester, and serial US examinations were performed in cases of low placentation. Placenta accreta spectrum was based on clinical findings and confirmed by histologic results.

RESULTS

Of 68 women, 40 (59%) had prior cesarean delivery (CD). Hysterectomy was performed in 8, all with prior CD. Of these, 7 (88%) had US suspicion of PAS. In 16 with prior CD and basalis overlying the internal os, 9 (56%) had second-trimester placenta previa, and 7 of 9 (78%) underwent hysterectomy with pathologic confirmation of PAS. Of 28 without prior CD, there were no cases of persistent low placentation in the third trimester regardless of the trophoblast location. Ultrasound parameters associated with PAS were a smaller distance from the inferior trophoblastic border to the external os, disruption of the bladder-serosal interface, bridging vessels, anechoic areas, and the SMT. In women with prior CD, use of the SMT in the sagittal plane yielded an area under the receiver operating characteristic curve of 0.96 (95% confidence interval, 0.91-1.00).

CONCLUSIONS

First-trimester low implantation increases the risk of persistent placenta previa and PAS in women with prior CD. All parameters were associated with PAS, the most predictive being the SMT.

Cesarean Scar Pregnancy Successfully Managed to Term: When the Patient Is Determined to Keep the Pregnancy

Cesarean scar pregnancy (CSP) is a rare form of ectopic pregnancy, defined as the implantation of the gestational sac at the uterine incision scar of the previous cesarean section. This condition is associated with severe maternal and fetal/neonatal complications, including severe bleeding, rupture of the uterus, fetal demise, or preterm delivery. In view of these, early diagnosis allows the option of termination of pregnancy. In this case report, we present a patient with a cesarean scar pregnancy who was diagnosed at the sixth week of gestation but declined early termination of the pregnancy and was managed to the 38th week. Placenta previa was confirmed in the second trimester. A planned cesarean section was performed that resulted in the birth of a live full-term neonate. Intraoperatively, placenta percreta was diagnosed, and due to uncontrollable bleeding, a hysterectomy was performed. The postoperative course was uneventful. In cases where an early diagnosis of CSP is made, women should be counseled that this will almost certainly evolve to placenta previa, and the associated risks should be explained. Close follow-up of CSP is mandatory if expectant management is selected. Further studies are needed for definitive conclusions and to determine the risks of expectant management.

Minimizing surgical blood loss at cesarean hysterectomy for placenta previa with evidence of placenta increta or placenta percreta: the state of play in 2020

The evolution of multidisciplinary team-based care for women with placenta accreta spectrum disorder has delivered stepwise improvements in clinical outcomes. Central to this overall goal is the ability to limit blood loss at surgery. Placement of inflatable balloons within the pelvic arteries, most commonly in the anterior divisions of the internal iliac arteries, became popular in many centers, at the expense of prolonging surgical care and with attendant risks of vascular injury. In tandem, the need to expose pelvic sidewall anatomy to safely identify the course of the ureters re-popularized the alternative strategy of ligating the same anterior divisions of the internal iliac arteries. With incremental gains in surgical expertise, described in 5 steps in this review, our teams have witnessed a steady decline in surgical blood loss. Nevertheless, a subset of women has the most severe form of placenta accreta spectrum, namely placenta previa-percreta. Such women are at risk of major hemorrhage during surgery from vessels arising outside the territories of the internal iliac arteries. These additional blood supplies, mostly from the external iliac arteries, pose significant risks of major blood loss even in experienced hands. To address this risk, some centers, principally in China, have adopted an approach of routinely placing an infrarenal aortic balloon, with both impressively low rates of blood loss and an ability to conserve the uterus by resecting the placenta with the affected portion of the uterine wall. We review these literature developments in the context of safely performing elective cesarean hysterectomy for placenta previa-percreta, the most severe placenta accreta spectrum disorder.

Spontaneous Rupture in a Non-Laboring Uterus at 20 Weeks: A Case Report

Patient: Female, 31-year-old

Final Diagnosis: Uterine rupture secondary to placenta percreta

Symptoms: Acute abdomen

Medication: —

Clinical Procedure: Laparotomy and subtotal hysterectomy

Specialty: Obstetrics and Gynecology

Early prediction of placenta accreta spectrum in women with prior cesarean delivery using transvaginal ultrasound at 11 to 14 weeks

BACKGROUND

There is a growing body of evidence that sonographic signs of placenta accreta spectrum can be observed in the first trimester of pregnancy. The most significant marker is placental location next to or in the scar niche in women with a prior cesarean delivery.

OBJECTIVE

This study aimed to assess the performance of transvaginal ultrasound in the early prediction of placenta accreta spectrum in women with a prior cesarean delivery.

STUDY DESIGN

This was a retrospective cohort of women with a history of cesarean delivery who had transvaginal ultrasound at 11 to 14 weeks' gestation between September 2016 and May 2018. Ultrasound reports were reviewed and graded for suspicion of placenta accreta spectrum as follows: Grade 0 (no suspicion) if the placenta is not next to the scar; Grade 1 (intermediate suspicion) if the placenta is next or on the scar; Grade 2 (high suspicion) if the placenta was inside the scar niche. In addition, all images were reviewed and graded by trained specialists blinded to the outcome. The primary outcome was a histologic diagnosis of placenta accreta spectrum. Sensitivity, specificity, positive predictive value, and negative predictive value of first-trimester transvaginal ultrasound to detect placenta accreta spectrum were assessed.

RESULTS

In this study, 467 patients were included, and 8 (1.7%) had placenta accreta spectrum at delivery. Using the original report, 442 patients (94.6%) were Grade 0, 20 (4.3%) Grade 1, and 5 (1.1%) Grade 2. The revised grading had 456 patients (97.6%) with Grade 0, 5 (1.1%) with Grade 1, and 6 (1.3%) with Grade 2. Patients with Grade 2 yielded a sensitivity of 62.5% (95% confidence interval, 24.5-91.5), specificity of 100% (95% confidence interval, 99.2-100.0), positive predictive value of 100% (95% confidence interval, 97.0-100.0), and negative predictive value of 99.4% (95% confidence interval, 98.4-99.7). Any sonographic suspicion of placenta accreta spectrum (Grade 1 or Grade 2) had a sensitivity of 75% (95% confidence interval, 34.9-96.8), specificity of 95.9% (95% confidence interval, 93.6-97.5), positive predictive value of 24% (95% confidence interval, 14.8-36.4), and negative predictive value of 99.6% (95% confidence interval, 98.5-99.9). The blinded image review yielded a better specificity (99.1% vs 95.9%; P=.001) and a positive predictive value (63.6% vs 24%; P=.02) with similar sensitivity (87.5% vs 75%; P=.52) and negative predictive value (99.8% vs 99.6%; P=.55).

CONCLUSION

Transvaginal ultrasound between 11 and 14 weeks' gestation in women a with prior cesarean delivery can identify at least 3 of 4 cases of placenta accreta spectrum. A finding of placental implantation within the scar niche has high positive predictive value for placenta accreta spectrum. Prospective studies are needed to assess routine screening for placenta accreta spectrum at 11 to 14 weeks' gestation in women with a prior cesarean delivery.