Third-trimester ultrasound for antenatal diagnosis of placenta accreta spectrum in women with placenta previa: results from the ADoPAD study

OBJECTIVE

To evaluate the performance of third-trimester ultrasound for the diagnosis of clinically significant placenta accreta spectrum disorder (PAS) in women with low-lying placenta or placenta previa.

METHODS

This was a prospective multicenter study of pregnant women aged ≥ 18 years who were diagnosed with low-lying placenta (< 20 mm from the internal cervical os) or placenta previa (covering the internal cervical os) on ultrasound at ≥ 26 + 0 weeks' gestation, between October 2014 and January 2019. Ultrasound suspicion of PAS was raised in the presence of at least one of these signs on grayscale ultrasound: (1) obliteration of the hypoechogenic space between the uterus and the placenta; (2) interruption of the hyperechogenic interface between the uterine serosa and the bladder wall; (3) abnormal placental lacunae. Histopathological examinations were performed according to a predefined protocol, with pathologists blinded to the ultrasound findings. To assess the ability of ultrasound to detect clinically significant PAS, a composite outcome comprising the need for active management at delivery and histopathological confirmation of PAS was considered the reference standard. PAS was considered to be clinically significant if, in addition to histological confirmation, at least one of these procedures was carried out after delivery: use of hemostatic intrauterine balloon, compressive uterine suture, peripartum hysterectomy, uterine/hypogastric artery ligation or uterine artery embolization. The diagnostic performance of each ultrasound sign for clinically significant PAS was evaluated in all women and in the subgroup who had at least one previous Cesarean section and anterior placenta. Post-test probability was assessed using Fagan nomograms.

RESULTS

A total of 568 women underwent transabdominal and transvaginal ultrasound examinations during the study period. Of these, 95 delivered in local hospitals, and placental pathology according to the study protocol was therefore not available. Among the 473 women for whom placental pathology was available, clinically significant PAS was diagnosed in 99 (21%), comprising 36 cases of placenta accreta, 19 of placenta increta and 44 of placenta percreta. The median gestational age at the time of ultrasound assessment was 31.4 (interquartile range, 28.6-34.4) weeks. A normal hypoechogenic space between the uterus and the placenta reduced the post-test probability of clinically significant PAS from 21% to 5% in women with low-lying placenta or placenta previa in the third trimester of pregnancy and from 62% to 9% in the subgroup with previous Cesarean section and anterior placenta. The absence of placental lacunae reduced the post-test probability of clinically significant PAS from 21% to 9% in women with low-lying placenta or placenta previa in the third trimester of pregnancy and from 62% to 36% in the subgroup with previous Cesarean section and anterior placenta. When abnormal placental lacunae were seen on ultrasound, the post-test probability of clinically significant PAS increased from 21% to 59% in the whole cohort and from 62% to 78% in the subgroup with previous Cesarean section and anterior placenta. An interrupted hyperechogenic interface between the uterine serosa and bladder wall increased the post-test probability for clinically significant PAS from 21% to 85% in women with low-lying placenta or placenta previa and from 62% to 88% in the subgroup with previous Cesarean section and anterior placenta. When all three sonographic markers were present, the post-test probability for clinically significant PAS increased from 21% to 89% in the whole cohort and from 62% to 92% in the subgroup with previous Cesarean section and anterior placenta.

CONCLUSIONS

Grayscale ultrasound has good diagnostic performance to identify pregnancies at low risk of PAS in a high-risk population of women with low-lying placenta or placenta previa. Ultrasound may be safely used to guide management decisions and concentrate resources on patients with higher risk of clinically significant PAS. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal ultrasound staging system for placenta accreta spectrum disorders

OBJECTIVES

To develop a prenatal ultrasound staging system for placenta accreta spectrum (PAS) disorders in women with placenta previa and to evaluate its association with surgical outcome, placental invasion and the clinical staging system for PAS disorders proposed by the International Federation of Gynecology and Obstetrics (FIGO).

METHODS

This was a secondary retrospective analysis of prospectively collected data from women with placenta previa. We classified women according to the following staging system for PAS disorders, based upon the presence of ultrasound signs of PAS in women with placenta previa: PAS0, placenta previa with no ultrasound signs of invasion or with placental lacunae but no evidence of abnormal uterus-bladder interface; PAS1, presence of at least two of placental lacunae, loss of the clear zone or bladder wall interruption; PAS2, PAS1 plus uterovescical hypervascularity; PAS3, PAS1 or PAS2 plus evidence of increased vascularity in the inferior part of the lower uterine segment potentially extending into the parametrial region. We explored whether this ultrasound staging system correlates with surgical outcome (estimated blood loss (EBL, mL), units of packed red blood cells (PRBC), fresh frozen plasma (FFP) and platelets (PLT) transfused, operation time (min), surgical complications defined as the occurrence of any damage to the bladder, ureters or bowel, length of hospital stay (days) and admission to intensive care unit (ICU)) and depth of placental invasion. The correlation between the present ultrasound staging system and the clinical grading system proposed by FIGO was assessed. Prenatal and surgical management were not based on the proposed prenatal ultrasound staging system. Linear and multiple regression models were used.

RESULTS

Two-hundred and fifty-nine women were included in the analysis. Mean EBL was 516 ± 151 mL in women with PAS0, 609 ± 146 mL in those with PAS1, 950 ± 190 mL in those with PAS2 and 1323 ± 533 mL in those with PAS3, and increased significantly with increasing severity of PAS ultrasound stage. Mean units of PRBC transfused were 0.05 ± 0.21 in PAS0, 0.10 ± 0.45 in PAS1, 1.19 ± 1.11 in PAS2 and 4.48 ± 2.06 in PAS3, and increased significantly with PAS stage. Similarly, there was a progressive increase in the mean units of FFP transfused from PAS1 to PAS3 (0.0 ± 0.0 in PAS1, 0.25 ± 1.0 in PAS2 and 3.63 ± 2.67 in PAS3). Women presenting with PAS3 on ultrasound had significantly more units of PLT transfused (2.37 ± 2.40) compared with those with PAS0 (0.03 ± 0.18), PAS1 (0.0 ± 0.0) or PAS2 (0.0 ± 0.0). Mean operation time was longer in women with PAS3 (184 ± 32 min) compared with those with PAS1 (153 ± 38 min) or PAS2 (161 ± 28 min). Similarly, women with PAS3 had longer hospital stay (7.4 ± 2.1 days) compared with those with PAS0 (3.4 ± 0.6 days), PAS1 (6.4 ± 1.3 days) or PAS2 (5.9 ± 0.8 days). On linear regression analysis, after adjusting for all potential confounders, higher PAS stage was associated independently with a significant increase in EBL (314 (95% CI, 230-399) mL per one-stage increase; P < 0.001), units of PRBC transfused (1.74 (95% CI, 1.33-2.15) per one-stage increase; P < 0.001), units of FFP transfused (1.19 (95% CI, 0.61-1.77) per one-stage increase; P < 0.001), units of PLT transfused (1.03 (95% CI, 0.59-1.47) per one-stage increase; P < 0.001), operation time (38.8 (95% CI, 31.6-46.1) min per one-stage increase; P < 0.001) and length of hospital stay (0.83 (95% CI, 0.46-1.27) days per one-stage increase; P < 0.001). On logistic regression analysis, increased severity of PAS was associated independently with surgical complications (odds ratio, 3.14 (95% CI, 1.36-7.25); P = 0.007), while only PAS3 was associated with admission to the ICU (P < 0.001). All women with PAS0 on ultrasound were classified as having Grade-1 PAS disorder according to the FIGO grading system. Conversely, of the women presenting with PAS1 on ultrasound, 64.1% (95% CI, 48.4-77.3%) were classified as having Grade-3, while 35.9% (95% CI, 22.7-51.6%) were classified as having Grade-4 PAS disorder, according to the FIGO grading system. All women with PAS2 were categorized as having Grade-5 and all those with PAS3 as having Grade-6 PAS disorder according to the FIGO system.

CONCLUSION

Ultrasound staging of PAS disorders is feasible and correlates with surgical outcome, depth of invasion and the FIGO clinical grading system. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Color Doppler energy imaging in the diagnosis of fetal intracranial hemorrhage in the second trimester

Unlike conventional color Doppler imaging; color Doppler energy (or power Doppler) displays the intensity of the returning Doppler signal, is less dependent on the orientation of the blood vessel, and is therefore better able to detect low blood velocities. For these reasons it could be useful in some investigations which are difficult to perform, such as transvaginal evaluation of fetal brain vessels. We report a case of a fetal intracranial hyperechoic lesion detected at 26 weeks by transabdominal sonography in a severely growth-retarded fetus. There was absence of diastolic flow in the umbilical artery and low impedance to diastolic flow in the middle cerebral arteries. The fetus was further investigated by transvaginal sonography for the evaluation of the nature and localization of the lesion and an intraventricular hemorrhage in the right brain parenchyma with disorganized supratentorial brain structure was observed. As color Doppler energy imaging is more sensitive to slow flow, it was more reliable than conventional Doppler imaging in confirming the absence of flow within and around the hyperechoic lesion in contrast to the normal vascularity of the contralateral ventricular system. After informed parental counselling, the mother, for psychological reasons, asked to be delivered by Cesarean section. The fetus died 24 h after birth. The autopsy corroborated the ultrasonographic diagnosis. This case report confirms the accuracy of transvaginal ultrasonography in the diagnosis of intracranial hemorrhage and suggests a specific role for color Doppler energy imaging.