Placenta accreta in the first trimester of pregnancy: sonographic findings

Placenta accreta spectrum in early and late pregnancy from an imaging perspective. A scoping review

Placenta accreta spectrum (PAS) disorders (with increasing order of the depth of invasion: accreta, increta, percreta) are quite challenging for the purpose of diagnosis and treatment. Pathological examination or imaging evaluation are not very dependable when considered as stand-alone diagnostic tools. On the other hand, timely diagnosis is of great importance, as maternal and fetal mortality drastically increases if patient goes through the third phase of delivery in a not well-suited facility. A multidisciplinary approach for diagnosis (incorporating clinical, imaging, and pathological evaluation) is mandatory, particularly in complicated cases. For imaging evaluation, the diagnostic modality of choice in most scenarios is ultrasound (US) exam; patients are referred for MRI when US is equivocal, inconclusive, or not visualizing placenta properly. Herewith, we review the reported US and MRI features of PAS disorders (mainly focusing on MRI), going over the normal placental imaging and imaging pitfalls in each section, and lastly, covering the imaging findings of PAS disorders in the first trimester and cesarean section pregnancy (CSP).

Cesarean Scar Pregnancy: A systematic review on expectant management

A Cesarean Scar Pregnancy (CSP) is a variant of uterine ectopic pregnancy defined by full or partial implantation of the gestational sac in the scar of a previous cesarean section. The continuous increase of Cesarean Deliveries is causing a parallel increase in CSP and its complications. Considering its high morbidity, the most usual recommendation has been termination of pregnancy in the first trimester; however, several cases progress to viable births. The aim of this systematic review is to evaluate the outcome of CSP managed expectantly and understand whether sonographic signs could correlate to the outcomes. An online-based search of PubMed and Cochrane Library Databases was used to gather studies including women diagnosed with a CSP who were managed expectantly. The description of all cases was analysed by the authors in order to obtain information for each outcome. 47 studies of different types were retrieved, and the gestational outcome was available in 194 patients. Out of these, 39 patients (20,1%) had a miscarriage and 16 (8,3%) suffered foetal death. 50 patients (25,8%) had a term delivery and 81 (41,8%) patients had a preterm birth, out of which 27 (13,9%) delivered before 34 weeks of gestation. In 102 (52,6%) patients, a hysterectomy was performed. Placenta Accreta Spectrum (PAS) was a common disorder among CSP and was linked to a higher rate of complications such as foetal death, preterm birth, hysterectomy, haemorrhagic morbidity and surgical complications. Some of the analysed articles showed that sonographic signs with specific characteristics, such as type II and III CSP classification, Crossover Sign - 1, "In the niche" implantation and lower myometrial thickness could be related to worse outcomes of CSP. This article provides a good understanding of CSP as an entity that, although rare, presents with a high rate of relevant morbidity. It is also understood that pregnancies with confirmed PAS had an even higher rate of morbidity. Some sonographic signs were shown to predict the prognosis of these pregnancies and further investigation is necessary to validate one or more signs so they can be used for a more reliable counselling of women with CSP.

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.

Extreme enhanced myometrial vascularity following cesarean scar pregnancy: a new diagnostic entity

OBJECTIVE

To define, illustrate and to follow-up the diagnosis, pathophysiology and treatment of a subset of the known enhanced myometrial vascularity (EMV): its extreme form, associated with cesarean scar pregnancies (CSP) and with some cases pf placenta accreta spectrum being at increased risk of significant bleeding complications. We also aim to provide guidance to the management of such cases.

MATERIAL AND METHODS

This is an IRB-approved retrospective observational study of thirteen patients with an extreme form of EMV complicating CSPs. Patient's age, parity, number of cesarean deliveries, initial and time to negative serum hCG levels, primary and secondary diagnoses, blood flow peak systolic velocities, primary and secondary treatments, uterine artery embolization and outcomes were recorded.

RESULTS

Gestational ages ranged 6-11 weeks at initial presentation. Initial serum hCG was 20.0-102.48 mIU/L (mean 44.4 mIU/L). Diameter of EMV reached 20-75 mm (mean 46.8 mm). The mean peak systolic velocity (PSV) was 84.2 cm/s (range 46.7-118.0). Primary treatments were: systemic methotrexate (MTX) alone; D&C alone; MTX and D&C; local and systemic intra-gestational MTX injection; double cervical ripening balloon with systemic MTX; misoprostol and D&C; emergent UAE. UAE and hysterectomy were the two main secondary treatments in 10 women except 1 having a D&C after UAE, and in 1 the lesion regressed without secondary treatment. Mean time to nonpregnant hCG levels was 21-122 days (mean 67.2). Mean follow-up was 110.2 days (range 26-160). Ten women were treated with UAE, 6 had one, 3 had two embolizations. Two women had hysterectomies, one of these for persistent bleeding. Based upon the common denominators of the clinical and the US pictures, our definition of extreme EMV is sustained form of EMV associated with treated or untreated CSP, with peak systolic velocities of blood flow over 50 cm/s, slow return or plateauing serum hCG, with or without clinically significant vaginal bleeding, unresponsive to initial or secondary treatment requiring uterine artery embolization or hysterectomy.

CONCLUSION

The EMV developing in the background of retained placental tissue associated with CSP differs following the normal regression of the physiologically re-modelled, dilated vascular bed from the faulty "disrepair" of the vessel wall in in treated or untreated CSPs. The "threatening" appearance of the above EMVs warranted the term "extreme", creating their separate new sub-category." Extreme forms of CSP-related EMV pose significant diagnostic and management challenges. Prompt recognition and intervention, the proactive use of UAE, can maximize the outcome of women affected by this "extreme" form of EMV enabling to preserve reproductive potential. Obstetricians, gynecologists and interventional radiologists should be aware of this form of severe vascular complication.

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: Patient Counseling and Management

There is no universally agreed upon and adopted management protocol supported by professional societies in the United States or around the world for the treatment of cesarean scar pregnancy. There is a wide range of management options in the literature, and many of them can to lead to severe bleeding complications, which can result in loss of fertility or even maternal death. If inadequately managed, it can lead to untoward complications throughout all 3 trimesters of the pregnancy. Early detection of CSP has a paramount clinical importance.

Expectant management of caesarean scar ectopic pregnancy: a systematic review

AIM

The purpose of this review is to systematically review all the reported cases and case series of caesarean scar pregnancy (CSP) managed expectantly without any intervention in order to understand the outcomes of pregnancy which will guide clinicians and patients in making treatment choices.

METHODS

An electronic search on PubMed, EMBASE and Cochrane databases and a manual search from references of the articles were performed. Studies were selected based on inclusion and exclusion criteria. Data were extracted for various outcomes of pregnancy and the quality of the reports was assessed using a modified Delphi technique.

RESULTS

A total of 56 cases of CSP from 11 reports were included in the review, including 44 cases with foetal cardiac activity. Live births were achieved in 73% of cases with a quarter of them born before 34 weeks. Hysterectomy rates were 70%. In 12/44 (27%) of cases pregnancies were lost due to complications before 24 weeks. Most (67%) of the CSPs with no foetal cardiac activities resolved on expectant management and the remaining required intervention for bleeding.

CONCLUSIONS

Caution should be exercised when choosing expectant management in cases of viable CSPs, and if chosen, the patient should be counselled adequately for possible outcomes including loss of pregnancy and hysterectomy. Expectant management is acceptable in CSPs with no foetal cardiac activity. There is a need for prospective research on this topic with adequate reporting on possible prognostic markers, as well as a need to improve on the techniques to prevent loss of fertility during delivery.

Successful pregnancy located in a uterine cesarean scar: A case report

Cesarean scar pregnancy (CSP) is a rare form of ectopic pregnancy. Because CSP carries a high risk of uterine rupture and life-threatening bleeding, the pregnancy should be terminated upon confirmation of diagnosis. There have been few reports of CSP with successful delivery. We present a case of CSP under expectant management, with delivery via planned cesarean section at 35 weeks of gestation. This report suggests that successful pregnancy outcome can be achieved in some women with uterine cesarean scar, but further analysis and additional studies are required in order to describe the optimal protocol of expectant management in CSP.

Accreta placentation: a systematic review of prenatal ultrasound imaging and grading of villous invasiveness

BACKGROUND

Determining the depth of villous invasiveness before delivery is pivotal in planning individual management of placenta accreta. We have evaluated the value of various ultrasound signs proposed in the international literature for the prenatal diagnosis of accreta placentation and assessment of the depth of villous invasiveness.

OBJECTIVE

We undertook a PubMed and MEDLINE search of the relevant studies published from the first prenatal ultrasound description of placenta accreta in 1982 through March 30, 2016, using key words "placenta accreta," "placenta increta," "placenta percreta," "abnormally invasive placenta," "morbidly adherent placenta," and "placenta adhesive disorder" as related to "sonography," "ultrasound diagnosis," "prenatal diagnosis," "gray-scale imaging," "3-dimensional ultrasound", and "color Doppler imaging."

STUDY DESIGN

The primary eligibility criteria were articles that correlated prenatal ultrasound imaging with pregnancy outcome. A total of 84 studies, including 31 case reports describing 38 cases of placenta accreta and 53 series describing 1078 cases were analyzed. Placenta accreta was subdivided into placenta creta to describe superficially adherent placentation and placenta increta and placenta percreta to describe invasive placentation.

RESULTS

Of the 53 study series, 23 did not provide data on the depth of villous myometrial invasion on ultrasound imaging or at delivery. Detailed correlations between ultrasound findings and placenta accreta grading were found in 72 cases. A loss of clear zone (62.1%) and the presence of bridging vessels (71.4%) were the most common ultrasound signs in cases of placenta creta. In placenta increta, a loss of clear zone (84.6%) and subplacental hypervascularity (60%) were the most common ultrasound signs, whereas placental lacunae (82.4%) and subplacental hypervascularity (54.5%) were the most common ultrasound signs in placenta percreta. No ultrasound sign or a combination of ultrasound signs were specific of the depth of accreta placentation.

CONCLUSION

The wide heterogeneity in terminology used to describe the grades of accreta placentation and differences in study design limits the evaluation of the accuracy of ultrasound imaging in the screening and diagnosis of placenta accreta. This review emphasizes the need for further prospective studies using a standardized evidence-based approach including a systematic correlation between ultrasound signs of placenta accreta and detailed clinical and pathologic examinations at delivery.

Sonographic Findings of Morbidly Adherent Placenta in the First Trimester

OBJECTIVES

The purpose of this study was to evaluate the association between first-trimester sonographic findings and morbidly adherent placenta at delivery.

METHODS

We conducted a retrospective review of all first-trimester sonographic examinations from pregnancies that underwent third-trimester sonography for placenta previa or low-lying placenta between September 1997 and October 2011. Only women with a prior cesarean delivery were included. Transabdominal and transvaginal images from these first-trimester studies were reviewed for the following sonographic parameters: distance from the inferior border of the gestational sac to the external cervical os, location of the decidua basalis, presence of anechoic areas, uterine-bladder interface irregularity, and smallest anterior myometrial thickness. Morbidly adherent placentation was confirmed on histologic examination of hysterectomy specimens. Statistical methods included univariate and multivariate analyses.

RESULTS

Thirty-nine patients met inclusion criteria, of whom 14 (36%) had confirmed placental invasion. The number of prior cesarean deliveries was significantly associated with placental invasion (P < .0001). The only first-trimester sonographic finding associated with invasion was the smallest anterior myometrial thickness measured in the sagittal plane (P < .02). Multivariate analysis based on these two variables yielded an area under the receiver operating characteristic curve of 0.94 (95% confidence interval, 0.87-1.00) and significantly improved the prediction of placental invasion compared to using the number of prior cesarean deliveries alone.

CONCLUSIONS

In women with persistent placenta previa or low-lying placenta and prior cesarean delivery, the smallest anterior myometrial thickness on first-trimester sonography significantly improved detection of morbidly adherent placenta.

Natural history of early first-trimester pregnancies implanted in Cesarean scars

OBJECTIVE

To describe the ultrasound findings and natural history of pregnancies implanted within or on Cesarean section scars in the first trimester of pregnancy.

METHODS

This was a prospective observational study of 10 women diagnosed with a pregnancy implanted in or on a Cesarean section scar in the first trimester, who declined medical intervention because of their desire to continue the pregnancy. The study population comprised women at < 12 weeks' gestation who were seen in our early pregnancy unit between January 2011 and September 2013. Nine women were followed up by serial ultrasound examinations and had detailed care plans for delivery at King's College Hospital (KCH). One woman was followed up and delivered at another teaching hospital. The first-trimester ultrasound findings were compared with the clinical outcome of the pregnancy.

RESULTS

The nine patients who were followed up at KCH developed ultrasound findings of morbidly adherent placenta (MAP) in the second and third trimesters. All 10 patients were diagnosed with MAP at the time of delivery by Cesarean section. The gestational age at delivery ranged from 26 to 38 weeks. The uterus was conserved in five patients, and Cesarean hysterectomy was performed in the remaining five. All three women with complete implantation of the gestational sac within the scar and two of three cases with placental lakes in the first trimester had hysterectomies. The two cases with bulging of the gestational sac out of the uterine contour had a preterm emergency hysterectomy due to placenta percreta. Histology confirmed placenta accreta in the five hysterectomy specimens. There were no fetal or neonatal complications.

CONCLUSIONS

Implantation of a pregnancy on or in a Cesarean section scar is a precursor of MAP; however, the degree of morbidity associated with this implantation is variable and difficult to predict based on first-trimester ultrasound findings only. The assessment of ongoing pregnancies implanted in Cesarean scars is most beneficial when performed between 7 and 9 weeks' gestation. Complete implantation within the myometrial defect, bulging of the trophoblast from the uterine contour and large placental lakes in the first trimester are ultrasound findings that may predict severe placenta accreta or percreta and consequently a poor outcome.

Cesarean scar pregnancy and early placenta accreta share common histology

OBJECTIVE

To determine, by evaluation of histological slides, images and descriptions of early (second-trimester) placenta accreta (EPA) and placental implantation in cases of Cesarean scar pregnancy (CSP), whether these are pathologically indistinguishable and whether they both represent different stages in the disease continuum leading to morbidly adherent placenta in the third trimester.

METHODS

The database of a previously published review of CSP and EPA was used to identify articles with histopathological descriptions and electronic images for pathological review. When possible, microscopic slides and/or paraffin blocks were obtained from the original researchers. We also included from our own institutions cases of CSP and EPA for which pathology specimens were available. Two pathologists examined all the material independently and, blinded to each other's findings, provided a pathological diagnosis based on microscopic appearance. Interobserver agreement in diagnosis was determined.

RESULTS

Forty articles were identified, which included 31 cases of CSP and 13 cases of EPA containing histopathological descriptions and/or images of the pathology. We additionally included six cases of CSP and eight cases of EPA from our own institutions, giving a total of 58 cases available for histological evaluation (37 CSP and 21 EPA) containing clear definitions of morbidly adherent placenta. In the 29 cases for which images/slides were available for histopathological evaluation, both pathologists attested to the various degrees of myometrial and/or scar tissue invasion by placental villi with scant or no intervening decidua, consistent with the classic definition of morbidly adherent placenta. Based on the reviewed material, cases with a diagnosis of EPA and those with a diagnosis of CSP showed identical histopathological features. Interobserver correlation was high (kappa = 0.93).

CONCLUSIONS

EPA and placental implantation in CSP are histopathologically indistinguishable and may represent different stages in the disease continuum leading to morbidly adherent placenta in the third trimester.

Maternal and fetal outcomes in placenta accreta after institution of team-managed care

INTRODUCTION

Placenta accreta significantly contributes to maternal morbidity and mortality. We evaluated whether planned delivery and experienced, team-managed surgical intervention results in improved outcomes. We also examined whether risk factors differed for accreta, increta, and percreta and evaluated whether excess lower segment uterine vascularity correlates with disease severity.

METHODS

We retrospectively analyzed patients before versus after institution of a management protocol. Of the 58 044 deliveries over 10 years, there were 67 women whose pregnancies were histopathologically confirmed as placenta accreta, increta, or percreta (1/866). Clinical outcome measures were estimated blood loss (EBL), packed red blood cells (pRBCs) transfused, maternal and fetal complications, intensive care unit admission, and length of stay.

RESULTS

There were no maternal or infant deaths. In the managed cohort, EBL was reduced by 48% (P < .001), intraoperative pRBCs transfused by 40% (P < .01), total transfused pRBCs per case by 50% (P < .01), and surgical intensive care unit admissions by >50% (P < .01). Assessment of maternal risk factors by diagnosis revealed marked differences between accreta versus increta and percreta. Clinically assessed excess vascularity of the lower uterine segment correlated with disease severity. The incidence of neonatal complications was similar in both cohorts.

CONCLUSIONS

Targeted delivery at 34 weeks and team-managed diagnosis, treatment, and care of patients with placenta accreta were associated with improved maternal, but not neonatal outcomes.

Sonographic features of placenta accreta after first-trimester abortion

We assessed 5 patients with histologically/clinically confirmed placenta accreta after first-trimester abortion. In 4 patients, sonography showed an unclear endometrium, absence of an endometrium-myometrium interface, a well-vascularized hyperechoic lesion in the uterine body with a low resistive index, and myometrial thinning near the lesion. In 2 patients, contrast-enhanced sonography showed rapid irregular lesion enhancement. Chemotherapy reduced the lesions in 3 patients, and a decreased blood supply increased the resistive index in all lesions. Two patients each underwent hysterectomy and uterine curettage. The fifth patient had a cervical pregnancy; sonography showed a well-vascularized hyperechoic lesion in an enlarged cervix. Methotrexate gradually reduced this lesion. Sonography, especially contrast-enhanced sonography, can detect placenta accreta and guide treatment.

Identifying sonographic markers for placenta accreta in the first trimester

Our study attempted to identify whether sonographic markers for placenta accreta may be present as early as the first trimester. We reviewed 10 cases with pathologically proven accreta and retrospectively analyzed their first-trimester images. The gestational ages ranged from 8 weeks 4 days to 14 weeks 2 days. Sonographic findings included anechoic placental areas (9 of 10), low implantation of the gestational sac (9 of 10), an irregular placental-myometrial interface (9 of 10), and placenta previa (7 of 10). Nine patients had at least 1 prior cesarean delivery; 3 had additional uterine surgical procedures. One patient underwent hysteroscopic myomectomy. Our case series suggests that signs of placenta accreta may be present in the first trimester.

[Case study of a severe hemorrhage during a dilatation and curettage: Arteriovenous malformation or first trimester placenta accreta?]

A 27-year-old woman had a uterine curettage that was complicated by a severe hemorrhage. Ultrasonography and MRI showed a vascular lesion of the uterine fundus suspected to be an atypical arteriovenous malformation. The lesion spontaneously disappeared 2months later. The two most likely diagnoses are an arteriovenous malformation or a placenta accreta. The aim is to discuss the etiology of this serious complication from a case report of a severe hemorrhage during a uterine curettage.

Sonographic study of the decidua basalis in the first trimester of pregnancy

OBJECTIVES

To describe the sonographic appearance of the decidua basalis and its changes in the first trimester of pregnancy.

METHODS

We reviewed images from 159 first-trimester ultrasound examinations in 105 women with uncomplicated pregnancies who later delivered at term. The appearance of the decidua basalis layer and the sonographic changes that it underwent, including in echogenicity and thickness, were analyzed with respect to gestational age.

RESULTS

A distinct decidual layer could be identified consistently at 5-6 weeks' gestation and its thickness peaked at 6-7 weeks. It was seen inconsistently at 8-9 weeks and was not identifiable by 10 weeks. Its appearance changed over time, from a uniformly echogenic layer at 5-6 weeks to a heterogeneous echogenic layer at 7 weeks, corresponding to the histological evidence of trophoblast penetration. The layer then became less echogenic with time until it became unidentifiable.

CONCLUSIONS

There is a window of opportunity in the first trimester for sonographic examination of the decidua. This may allow screening, at an early stage, for conditions that affect the decidua during pregnancy.