Prenatal diagnosis of placenta previa/accreta with color Doppler ultrasound

Placenta accreta spectrum conservative management and coagulopathy: case series and systematic review

OBJECTIVE

Management of placenta accreta spectrum (PAS) with the placenta kept in situ aims to preserve fertility and minimize blood loss. However, this method is associated with a risk of coagulopathy and subsequent bleeding. The aim of this study was to evaluate the occurrence and pathophysiology of coagulopathy in cases of PAS managed conservatively.

METHODS

We reviewed our database for cases of PAS in which the placenta was kept in situ. In addition, we performed a systematic review of articles on PAS in which the placenta was left in situ and was complicated by coagulopathy. PubMed was searched for publications between 1980 and 2023. Our eligibility criteria included studies in which no additional interventions were performed other than keeping the placenta entirely in situ, and in which coagulopathy was reported.

RESULTS

After screening and selection of full-text articles, 10 studies were included in the review. A review of our databases yielded a case series of PAS managed conservatively with the placenta kept in situ. When adding our case series to the results of our systematic review, a total of 87 cases were found to have been managed conservatively, with 28 cases of coagulopathy. Of these, the time at which coagulopathy developed was known in 11 cases. The median time at development of coagulopathy was 58 (interquartile range, 50-67) days postpartum.

CONCLUSIONS

Our findings highlight that conservative management of PAS with the placenta in situ poses a risk of coagulopathy. Keeping the placenta in situ after delivery prolongs the risk factors that are integral to PAS. The pathophysiology behind coagulopathy is comparable with that of concealed placental abruption, due to the disrupted uteroplacental interface and the collection of blood in the placenta. Therefore, the presence of large placental lakes could be an indicator of developing coagulopathy. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Modified Delphi study of ultrasound signs associated with placenta accreta spectrum

OBJECTIVE

To determine, by expert consensus through a modified Delphi process, the role of standardized and new ultrasound signs in the prenatal evaluation of patients at high risk of placenta accreta spectrum (PAS).

METHODS

A systematic review of articles providing information on ultrasound imaging signs or markers associated with PAS was performed before the development of questionnaires for the first round of the Delphi process. Only peer-reviewed original research studies in the English language describing one or more new ultrasound sign(s) for the prenatal evaluation of PAS were included. A three-round consensus-building Delphi method was then conducted under the guidance of a steering group, which included nine experts who invited an international panel of experts in obstetric ultrasound imaging in the evaluation of patients at high risk for PAS. Consensus was defined as agreement of ≥ 70% between participants.

RESULTS

The systematic review identified 15 articles describing eight new ultrasound signs for the prenatal evaluation of PAS. A total of 35 external experts were approached, of whom 31 agreed and participated in the first round. Thirty external experts (97%) and seven experts from the steering group completed all three Delphi rounds. A consensus was reached that a prior history of at least one Cesarean delivery, myomectomy or PAS should be an indication for detailed PAS ultrasound assessment. The panelists also reached a consensus that seven of the 11 conventional signs of PAS should be included in the examination of high-risk patients and the routine mid-gestation scan report: (1) loss of the 'clear zone', (2) myometrial thinning, (3) bladder-wall interruption, (4) placental bulge, (5) uterovesical hypervascularity, (6) placental lacunae and (7) bridging vessels. A consensus was not reached for any of the eight new signs identified by the systematic review. With respect to other ultrasound features that are not specific to PAS but increase the probability of PAS at birth, the panelists reached a consensus for the finding of anterior placenta previa or placenta previa with cervical involvement. The experts were also asked to determine which PAS signs should be quantified and consensus was reached only for the quantification of placental lacunae using an existing score. For predicting surgical outcome in patients with a high probability of PAS at delivery, a consensus was obtained for loss of the clear zone, bladder-wall interruption, presence of placental lacunae and presence of placenta previa involving the cervix.

CONCLUSIONS

We have confirmed the continued importance of seven established standardized ultrasound signs of PAS, highlighted the role of transvaginal ultrasound in evaluating the placental position and anatomy of the cervix, and identified new ultrasound signs that may become useful in the future prenatal evaluation and management of patients at high risk for PAS at birth. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Evaluation of classic and novel ultrasound signs of placenta accreta spectrum

OBJECTIVES

Improvement in the antenatal diagnosis of placenta accreta spectrum (PAS) would allow preparation for delivery in a referral center, leading to decreased maternal morbidity and mortality. Our objectives were to assess the performance of classic ultrasound signs and to determine the value of novel ultrasound signs in the detection of PAS.

METHODS

This was a retrospective cohort study of women with second-trimester placenta previa who underwent third-trimester transvaginal ultrasound and all women with PAS in seven medical centers. A retrospective image review for signs of PAS was conducted by three maternal-fetal medicine physicians. Classic signs of PAS were defined as placental lacunae, bladder-wall interruption, myometrial thinning and subplacental hypervascularity. Novel signs were defined as small placental lacunae, irregular placenta-myometrium interface (PMI), vascular PMI, non-tapered placental edge and placental bulge towards the bladder. PAS was diagnosed based on difficulty in removing the placenta or pathological examination of the placenta. Multivariate regression analysis was performed and receiver-operating-characteristics (ROC) curves were generated to assess the performance of combined novel signs, combined classic signs and a model combining classic and novel signs.

RESULTS

A total of 385 cases with placenta previa were included, of which 55 had PAS (28 had placenta accreta, 11 had placenta increta and 16 had placenta percreta). The areas under the ROC curves for classic markers, novel markers and a model combining classic and novel markers for the detection of PAS were 0.81 (95% CI, 0.75-0.88), 0.84 (95% CI, 0.77-0.90) and 0.88 (95% CI, 0.82-0.94), respectively. A model combining classic and novel signs performed better than did the classic or novel markers individually (P = 0.03). An increasing number of signs was associated with a greater likelihood of PAS. With the presence of 0, 1, 2 and ≥ 3 classic ultrasound signs, PAS was present in 5%, 24%, 57% and 94% of cases, respectively.

CONCLUSIONS

We have confirmed the value of classic ultrasound signs of PAS. The use of novel ultrasound signs in combination with classic signs improved the detection of PAS. These findings have clinical implications for the detection of PAS and may help guide the obstetric management of patients diagnosed with these placental disorders. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

US and MR imaging findings to detect placental adhesion spectrum (PAS) in patients with placenta previa: a comparative systematic study

PURPOSE

To compare the performance US and MR in identifying placental adhesion spectrum (PAS) in placenta previa (PP) and to establish a potential method of image interpretation.

METHODS

US and MR examinations of 51 patients with PP were selected. The presence of imaging signs commonly used to detect PAS was assessed. Penalized logistic regression was performed considering histology as standard of reference; only signs statistically significant (p < 0.05) were considered for ROC and multivariate analysis. The probability of PAS according to the presence of US and/or MR signs was then assessed.

RESULTS

At univariate analysis, loss of retroplacental clear space, myometrial thinning (MT) and placenta lacunar spaces on US, intraplacental dark bands (IDBs), focal interruption of myometrial border (FIMB) and abnormal vascularity (AV) on MR were statistically significant (p < 0.01). Three diagnostic methods for PAS were then developed for both US and MR when at least one (Method 1), two (Method 2) or three (Method 3) imaging signs occurred, respectively. Method 2 for MR showed a significantly (p < 0.05) higher accuracy (91%) compared to the other methods. When MR IDBs and AV as well as IDBs and FIMB were present in combination with US MT the probability of PAS increased from 75 to 90% and from 80 to 91%, respectively.

CONCLUSION

MR demonstrated a higher diagnostic accuracy than US to detect PAS. However, since the combination of MR and US signs could improve the probability to detect PAS, a complementary diagnostic role of these techniques could be considered.

Placenta accreta spectrum: pathophysiology and evidence-based anatomy for prenatal ultrasound imaging

Placenta accreta spectrum is a complex obstetric complication associated with high maternal morbidity. It is a relatively new disorder of placentation, and is the consequence of damage to the endometrium-myometrial interface of the uterine wall. When first described 80 years ago, it mainly occurred after manual removal of the placenta, uterine curettage, or endometritis. Superficial damage leads primarily to an abnormally adherent placenta, and is diagnosed as the complete or partial absence of the decidua on histology. Today, the main cause of placenta accreta spectrum is uterine surgery and, in particular, uterine scar secondary to cesarean delivery. In the absence of endometrial reepithelialization of the scar area the trophoblast and villous tissue can invade deeply within the myometrium, including its circulation, and reach the surrounding pelvic organs. The cellular changes in the trophoblast observed in placenta accreta spectrum are probably secondary to the unusual myometrial environment in which it develops, and not a primary defect of trophoblast biology leading to excessive invasion of the myometrium. Placenta accreta spectrum was separated by pathologists into 3 categories: placenta creta when the villi simply adhere to the myometrium, placenta increta when the villi invade the myometrium, and placenta percreta where the villi invade the full thickness of the myometrium. Several prenatal ultrasound signs of placenta accreta spectrum were reported over the last 35 years, principally the disappearance of the normal uteroplacental interface (clear zone), extreme thinning of the underlying myometrium, and vascular changes within the placenta (lacunae) and placental bed (hypervascularity). The pathophysiological basis of these signs is due to permanent damage of the uterine wall as far as the serosa, with placental tissue reaching the deep uterine circulation. Adherent and invasive placentation may coexist in the same placental bed and evolve with advancing gestation. This may explain why no single, or set combination of, ultrasound sign(s) was found to be specific for the depth of abnormal placentation, and accurate for the differential diagnosis between adherent and invasive placentation. Correlation of pathological and clinical findings with prenatal imaging is essential to improve screening, diagnosis, and management of placenta accreta spectrum, and standardized protocols need to be developed.

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.

Prediction of morbidly adherent placenta using a scoring system

OBJECTIVE

To evaluate the accuracy of an ultrasound-based scoring system for diagnosing morbidly adherent placenta (MAP).

METHODS

This study included pregnant women referred to our ultrasound unit during 2013-2015 because of suspected MAP on a previous ultrasound examination or because they had at least one previous Cesarean delivery. All women were assessed using a scoring system based on the following: number and size of placental lacunae; obliteration of the demarcation between the uterus and placenta; placental location; color Doppler signals within placental lacunae; hypervascularity of the placenta-bladder and/or uteroplacental interface zone; and number of previous Cesarean deliveries. Each criterion was assigned 0, 1 or 2 points and the sum of points yielded the final score. Patients were classified into low, moderate or high probability for MAP based on the final score. The presence of MAP was determined by the surgeon at delivery and clinical descriptions were documented in the electronic patient file. Pathological diagnoses were available only in cases that underwent hysterectomy.

RESULTS

In total, 258 pregnant women were included in the study, of whom 23 (8.9%) were diagnosed with MAP. There was a statistically significant difference in the prevalence of MAP when women were grouped according to the scoring system, with 0.9%, 29.4% and 84.2% in the low, moderate and high probability groups, respectively (P < 0.0001). All sonographic criteria of the scoring system were significantly associated with MAP (P < 0.0001). Receiver-operating characteristics (ROC) curves for prediction of MAP using the number of placental lacunae and obliteration of the uteroplacental demarcation yielded an area under the ROC curve of 0.94 (95% CI, 0.86-1.00).

CONCLUSIONS

Our proposed scoring system is highly predictive of MAP in patients at risk. This allows an adequate multidisciplinary team approach for the planning and timing of delivery in such cases. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Morbidly Adherent Placenta: Interprofessional Management Strategies for the Intrapartum Period

"Morbidly adherent placenta" is a term that describes the continuum of placenta accreta, increta, and percreta. The incidence of this type of abnormal placentation has increased significantly over recent decades. The reason is probably multifactorial but, partly, because of factors such as the increasing number of cesarean births. Women at greatest risk are those who have myometrial damage caused by a previous cesarean birth, with either anterior or posterior placenta previa overlying the uterine scar. This condition poses significant risks of morbidity and/or mortality to the pregnant woman and her fetus. A multidisciplinary approach to care throughout pregnancy is essential. This article describes the classification of morbidly adherent placenta, risk factors, methods of diagnosis, potential maternal and fetal complications, and intrapartum clinical management strategies to optimize outcomes.

Does previa location matter? Surgical morbidity associated with location of a placenta previa

OBJECTIVE

To evaluate the effect of placenta previa location (anterior vs posterior) on cesarean morbidity.

STUDY DESIGN

Retrospective cohort of women undergoing cesarean for placenta previa. The rate of hysterectomy and blood transfusion in the setting of anterior previa was compared with posterior previa. Planned stratified analysis based on delivery history was performed. Logistic regression was performed to control for potential confounders.

RESULT

Two hundred and eighty-five women undergoing cesarean delivery for placenta previa were identified. Women undergoing primary cesareans with an anterior previa had higher rates of blood transfusion (adjusted odds ratio (aOR) 3.13 95% confidence interval (CI) (1.18 to 8.36) and hysterectomy (7.4% vs 0, P=0.001) compared with those with a posterior previa; similarly, women undergoing repeat cesarean with anterior previa had higher rates of hysterectomy (aOR 4.60 95% CI (1.02 to 20.7). The majority of hysterectomies (93.8%) were due to abnormal placentation.

CONCLUSION

An anterior placenta previa increases the risk of hysterectomy for both primary and repeat cesareans due to abnormal placentation. In the absence of accreta, blood transfusion remained a significant cause of maternal morbidity in both anterior and posterior placenta previas. This information may be useful for operative planning.

Color Doppler sonography in obstetrics and gynecology

This review aims to provide the reader with an overview of the present and future clinical applications in color Doppler sonography for the evaluation of vascularity and blood flow within the uterus (both gravid and nongravid), ovaries, fetus and placenta. The clinical use of color Doppler sonography has been demonstrated within many organ systems. Color Doppler sonography has become an integral part of cardiovascular imaging. Significant improvements have recently occurred, improving the visualization and evaluation of intra-organ vascularity, resulting from enhancements in delineation of tissue detail through electronic compounding and harmonics, as well as enhancements in signal processing of frequency- and/or amplitude-based color Doppler sonography. Spatial representation of vascularity can be improved by utilizing 3D and 4D (live 3D) processing. Greater sensitivity of color Doppler sonography to macro- and microvascular flow has provided improved anatomic and physiologic assessment throughout pregnancy and for pelvic organs. The potential use of contrast enhancement is also mentioned as a means to further differentiate benign from malignant ovarian lesions. The rapid development of these new sonographic techniques will continue to enlarge the scope of clinical applications in a variety of obstetric and gynecologic disorders.

[Comparative study of patients with placenta accreta with or without a history of cesarean section]

OBJECTIVE

To evaluate characteristics of placenta accreta (PA) in patients without previous cesarean section.

MATERIAL AND METHODS

Retrospective cohort study from December 1993 to April 2010 in two departments of obstetrics in university hospitals, Marseille, France. Comparison of clinical characteristics, circumstances of diagnosis, maternal morbidity and treatment was performed between PA diagnosed in patients with (n=63) and without prior cesarean section (n=35).

RESULTS

In group of patients without previous caesarean section, rate of placenta praevia, and antenatal diagnosis were lower (16/35 [46 %] vs. 44/63 [70 %], [P: 0.02]) and (4/35 [11 %] vs. 28/63 [44 %], [P<0.001]) and rate of pregnancies obtained by IVF was higher (5/35 [15 %] vs. 2/63 [3 %], [P=0.05]). In this group, no hysterectomy was performed but risk of uterus necrosis following embolization was increased (3/35 [8.6 %] patients vs. 0/63 patients [P: 0.02]).

CONCLUSIONS

Patients without previous caesarean section have specific characteristics in terms of risk factor and of management.

Placenta accreta and postpartum hemorrhage

Placenta accreta is the abnormal adherence of the placenta to the uterine wall. Where placenta accreta is present, the failure of the placenta to separate normally from the uterus after delivery is accompanied by severe postpartum hemorrhage. The best outcomes in placenta accreta are in prenatally diagnosed electively delivered cases. Management should take place in centers with special expertise. All obstetric units should have an obstetric hemorrhage protocol in place.

Imaging techniques to identify morbidly adherent placenta praevia: a prospective study

The objective of this study was to assess the sensitivity and specificity of Gray scale ultrasonography, magnetic resonance (MRI) and colour flow Doppler imaging in the diagnosis of morbidly adherent placenta praevia. We collected prospectively 30 cases of placenta praevia diagnosed by Gray scale ultrasound, colour flow Doppler and MRI. Delivery by elective caesarean section was carried out at the 38th week, before the onset of labour, unless obstetric complications supervened. Data regarding maternal outcome and newborn status were collected. Three patients had a morbid adherence of the placenta at delivery, two of whom required caesarean hysterectomy, and the other an internal iliac artery ligation. One patient was delivered at 33 weeks' gestation due to uncontrollable bleeding and the remainder were delivered at 38 weeks. All mothers and infants were well at the time of discharge. Colour flow Doppler was shown to be more specific in the diagnosis of the morbidly adherent placenta praevia than MRI. Doppler had a negative predictive value of 95%.

Placenta accreta: an association with fibroids and Asherman syndrome

OBJECTIVE

Placenta accreta is a life-threatening problem that is rising in incidence in the developed world. The increased risk of placenta accreta in women with placenta previa and 1 or more prior cesarean deliveries is well established and prompts careful sonographic evaluation. Our objective was to emphasize that accreta is also identified at sites other than cesarean scars.

METHODS

Two cases of placenta accreta without placenta previa seen in association with uterine scarring from myomectomy and uterine fibroids are described.

RESULTS

The sonographic and magnetic resonance imaging findings of accreta are reviewed in the classic setting of prior cesarean deliveries as well as myomectomy and uterine fibroids.

CONCLUSIONS

We suggest that when the placenta overlies any uterine abnormality, a careful search for invasive placentation is warranted.

MORBID ADHERENT PLACENTA: PREDICTION, DIAGNOSIS AND MANAGEMENT

Morbid adherent placenta (MAP), also known as placenta accreta, increta or percreta, is one of the main causes of maternal morbidity and mortality. Its incidence has noticeably increased in the last few decades, a fact directly related to the increase in caesarean sections. There is a close relation between iterative caesarean sections and MAP. This connection is of vital importance, since caesarean rates have risen worldwide, especially in the countries where there is the possibility of caesarean section on demand.

Sonographic findings of placental lacunae and the prediction of adherent placenta in women with placenta previa totalis and prior Cesarean section

OBJECTIVE

To investigate the value of transvaginal sonographic findings of intraplacental lacunae for predicting adherent placenta and clinical outcome in patients with placenta previa totalis and a history of Cesarean section.

METHODS

Fifty-one patients with placenta previa totalis diagnosed by transvaginal sonography and with a history of Cesarean section who delivered at our hospital were included in the study. The sonographic findings of intraplacental lacunae were classified into one of four grades. Pathological analysis of the placenta was performed for all patients who delivered, and in cases of hysterectomy, examination of the uterus was also performed. The placental findings and obstetric complications, including massive transfusion, intensive care unit admission and Cesarean hysterectomy, were compared with the grade of lacuna.

RESULTS

Lacunae were classified as Grade 1+ in 10 cases, Grade 2+ in 11 cases, Grade 3+ in five cases and as Grade 0 (i.e. lacunae were absent) in the remaining 25 cases. When lacunae of > or = Grade 1+ were considered, the sensitivity, specificity, positive predictive value and negative predictive value of diagnosing adherent placenta were 86.9%, 78.6%, 76.9% and 88.0%, respectively. When lacunae of > or = Grade 2+ were considered, the sensitivity, specificity, positive predictive value and negative predictive value of diagnosing placenta increta or percreta were 100%, 97.2%, 93.8% and 100%, respectively. Hysterectomy was performed in 18 cases, among whom two cases showed Grade 1+ lacunae, 11 cases showed Grade 2+ lacunae, and five cases showed Grade 3+ lacunae. No hysterectomy was performed in any case in which lacunae were absent. Compared to those without lacunae, the number of massive transfusions and intensive care unit admissions and cases of disseminated intravascular coagulopathy and Cesarean hysterectomy were significantly greater in those with lacunae (P < 0.0001).

CONCLUSION

Transvaginal sonographic findings of intraplacental lacunae in patients with placenta previa totalis and a history of Cesarean section are useful in the prediction of adherent placenta and may have a role in the prediction of clinical outcome.

Is placenta accreta catching up with us?

BACKGROUND

Concomitant with the increase in Caesarean birth over the past three decades there has been an apparent rise in the incidence of placenta accreta and its variants. The sequelae of an increase in the occurrence of abnormal placentation is the enhanced potential for severe maternal morbidity.

AIM

To determine the contempory demographics of placenta accreta over a 5-year period in a tertiary level teaching hospital.

METHODS

A retrospective review of all cases of placenta accreta and variants during the period of 1998-2002. Individual charts review followed case ascertainment via the hospital obstetric database.

RESULTS

Thirty-two women with placenta accreta (or variant) were identified. Median maternal age was 34 years, with a median parity of 2.5. Seventy-eight percent of cases had had at least one prior Caesarean birth, and 88% of cases were associated with placenta praevia. Pre-delivery ultrasonography was performed in all cases, providing diagnostic sensitivity of 63% and specificity of 43% with a predictive value of 76%. Hysterectomy was performed in 91% of cases with median intraoperative blood loss of 3000 mL. There were no maternal deaths in the current series.

CONCLUSION

A strong association between placenta accreta, placenta praevia and prior Caesarean birth has been demonstrated. As there is the potential for significant maternal morbidity the risk of placenta accreta needs to be recognised and women at risk should be considered for delivery at an institution with appropriate expertise and resources in managing this condition.

Placenta accreta diagnosed at 9 weeks' gestation

The majority of cases of placenta accreta are unanticipated and initially identified intraoperatively. Although color Doppler ultrasound is adequate for the evaluation of placenta accreta in the third trimester, ultrasound diagnosis in the first trimester has never been reported. To our knowledge, this is the first case of placenta accreta detected at 9 weeks' gestation by ultrasound. Placenta accreta with intraplacental lacunae can be identified together with a loss of the hypoechogenic retroplacental myometrial zone. Based on this case, we found that early diagnosis of placenta accreta in the first trimester by ultrasound is possible.

Complicated third stage of labor: time to switch on the scanner

This Editorial chronicles the current experience in ultrasound usage during pathologic events occurring in the third stage of labor. Further improvement in the technology for carrying out clinical research will improve our knowledge so that more information can be gleaned from this modality to bestow optimal management for such potentially dangerous conditions. Awareness of the capabilities of sonography may provide the motivation for its use, and obstetricians are encouraged to scan the third stage of normal deliveries for better recognition of normal findings and improved assessment of abnormal ones. Although final decisions should be based mainly upon sound clinical judgement, we contend that complicated third stage of labor warrants turning on the scanner.

Gray scale and color Doppler sonography in the third stage of labor for early detection of failed placental separation

OBJECTIVE

The purpose of this study was the characterization of normal and abnormal third stage placental separation using gray scale and color Doppler sonography.

METHODS

The third stage of labor was examined in 62 patients using gray scale and color Doppler sonography. After identification of placental basal plate vessels by color Doppler sonography, the placentation site was examined throughout the third stage with combined gray scale and color Doppler mode. Placental separation from the myometrium was defined clinically and correlated to cessation of color Doppler detected blood flow in basal plate vessels.

RESULTS

Three sonographic phases of placental separation were: (1) latent = interval between delivery of the fetus and beginning placental separation; (2) detachment = mono- or multiphasic shearing off of the placenta and (3) expulsion = interval between completed separation and vaginal delivery of the placenta. In 57 cases with clinically normal placental separation blood flow between placenta and myometrium ceased immediately after delivery of the fetus during the latent period. In five cases manual or instrumental removal was necessary because of placenta adhaerens in one case and placenta accreta in four cases. The latter showed maternal blood flow from the myometrium deep into the placenta beyond the latent phase.

CONCLUSION

Cessation of blood flow between the basal placenta and myometrium following delivery of the baby is the sonographic hallmark of normal placental separation. Persistent blood flow demonstrated by color Doppler sonography is suggestive of placenta accreta.

Prenatal diagnosis of placenta previa accreta by transabdominal color Doppler ultrasound

OBJECTIVE

The aim of this study was to evaluate the efficacy of transabdominal color Doppler ultrasound in diagnosing placenta previa accreta.

DESIGN

Eighty patients with persistent placenta previa underwent transabdominal B-mode and color Doppler ultrasound evaluation in the second and third trimesters because they had a high risk of placenta accreta. Color Doppler imaging criteria used included diffuse intraparenchymal placental lacunar flow; focal intraparenchymal placental lacunar flow; bladder-uterine serosa interphase hypervascularity; prominent subplacental venous complex; and loss of subplacental Doppler vascular signals. The color Doppler images were interpreted prospectively for signs of placenta previa accreta according to the exhibited color Doppler sonographic features.

RESULTS

Sixteen of the 80 patients exhibited characteristic color Doppler imaging patterns highly specific for placenta accreta according to the preceding criteria, and 14 of these had histopathological proof of placenta accreta. Two patients had false-positive color Doppler imaging evidence mistaken for interphase hypervascularity caused by bladder varices. Thirteen patients underwent hysterectomy in the group suspicious for accreta. Of the 64 patients with negative color Doppler imaging results, three had placenta accreta, while two required cesarean hysterectomy; the remaining patient underwent uterine artery ligation for bleeding from the lower uterine segment. The sensitivity of color Doppler imaging in the diagnosis of placenta previa accreta was 82.4% (14/17) and the specificity was 96.8% (61/63). The positive and negative predictive values were 87.5% (14/16) and 95.3% (61/64), respectively.

CONCLUSIONS

Variable vascular morphological patterns of placenta previa accreta were exhibited and categorized by transabdominal color Doppler sonography in the antenatal period. The identification of these specific vascular patterns had a positive impact on the peripartum clinical management of the affected patients.