Role of Placenta Accreta Index in Patients with Placenta Previa with Previous Cesarean: A Prospective Study

INTRODUCTION

Placenta accreta is a clinical condition when part of the placenta or the entire placenta invades the uterine wall and is inseparable from it.¹ Patients with placenta previa and prior cesarean sections have been shown to have an increased risk of placenta accreta based on a retrospective data analysis.² The types of placenta accreta based on the depth of invasion are placenta accreta vera (a partial but not full-thickness invasion into the myometrial layer), placenta increta (full-thickness myometrial invasion without penetration through the serosa layer), and placenta percreta (placental invasion through the uterine serosa). It is the common causes of peripartum emergency hysterectomy (51.1%)^3,4 and has been reported to cause 60% maternal morbidity and 7% mortality.^5,6 The current widespread use of imaging modalities in obstetrics has greatly advanced our ability to diagnose and manage abnormal obstetric bleeding. Considering the importance of antenatal diagnosis of abnormally invasive placenta, Rac et al.⁷ derived the placenta accreta index (PAI) score which was a 9-point score to improve the accuracy of accreta diagnosis. Ultrasound factors were developed using a linear regression modeling, multiparametric analysis, and receiver-operating characteristic (ROC) curve modeling to improve the prediction of abnormal placental invasion (Table 1).

The objectives of the study were to assess PAI score among cases of placenta previa with prior cesarean delivery and identification of cases of placenta accreta so as to find out appropriate cutoff of PAI score for early diagnosis of placenta accreta and its utility in predicting fetomaternal outcomes.

MATERIALS AND METHODS

It was a hospital-based descriptive type of observational study conducted prospectively in the Department of Obstetrics and Gynaecology in collaboration with the Department of Radiology and Department of Pathology, SMS Medical College, Jaipur, from April 2017 to November 2018. Eighty pregnant females with a period of gestation ≥28 weeks and a history of previous one or more cesarean arriving at the antenatal clinic or presenting with bleeding per vaginum underwent transabdominal sonography (TAS). Pregnant women with multifetal gestation, known coagulation disorders, and fetal distress requiring immediate emergency cesarean were excluded from the study. A thorough history was taken. General physical and obstetric examinations were performed. After taking a written informed consent to participate in the study, the pregnant females underwent ultrasonography to find out factors in favor of placenta accreta and to calculate the PAI score. Follow-up was done till 37 weeks of gestation (asymptomatic) or till termination (symptomatic). All patients underwent magnetic resonance imaging (MRI). Findings were correlated with that of ultrasonography (USG) and later with the operative findings. Basis of confirmation of placenta accreta cases was histopathological report. Findings were analyzed statistically to find out an appropriate cutoff value of PAI score, and fetomaternal outcomes were observed (Flowchart 1).

RESULTS

Figure 1 suggests that as the number of prior cesarean increases, the risk of placenta accreta also increases. All cases with previous three and previous four cesareans were diagnosed with placenta accreta in this study (p %3C; 0.05, significant).

Figure 2 suggests that the presence of lacunae acts as a risk factor for placenta accreta as increasing grade of lacunae is associated with more risk. In our study, all 30 patients with grade III lacunae were diagnosed with placenta accreta (p < 0.05, significant).

Figure 3 shows that sonographic finding of low retroplacental sagittal myometrial thickness (SMT) is a risk factor for placenta accreta. In our study, mean retroplacental SMT in cases with placenta accreta and without accreta was 2.82 ± 2.99 mm and 4.69 ± 1.34 mm, respectively. All those with SMT ≤ 1 mm were diagnosed with placenta accreta (p < 0.05, significant).

Figure 4 suggests that there is a positive association of placenta accreta with anterior placenta previa as 60% of such cases showed placenta accreta, while 30% with posterior placenta previa were diagnosed as accreta (p < 0.05, significant).

Figure 5 suggests that the presence of bridging vessels acts as a sonographic marker of placenta accreta, and in our study, all those with the presence of bridging vessels were confirmed with placenta accreta (p < 0.05, significant).

Figure 6 shows that on plotting ROC curve for different values of PAI score to predict placenta accreta, the area under curve (AUC) was found to be 0.958 with a cutoff value of %3E;2 (value with maximum sensitivity and specificity).

Table 2 suggests that more cases with placenta accreta were diagnosed by PAI score as compared with MRI per se.

Figure 7 shows that as the depth of invasion increases, the value of PAI score also increases, and higher scores are predictive of severity of invasion.

Figure 8 shows that as the number of previous cesarean increases, the value of PAI score also increases proportionately increasing the risk of placenta accreta.

Figure 9 shows that with increasing number of cesareans, probability and severity of invasion of placenta also increase.

Table 3 shows that on comparing the intraoperative findings, it was found that mean operative time, amount of blood loss, bladder injury or involvement, and requirement of hysterectomy was found more in cases of accreta with a PAI score of more than two.

On comparing the maternal outcomes, it was found that mean fall in hemoglobin, packed red cell transfusion, days of hospital stay, and maternal deaths were found more in cases of accreta with a PAI score more than two. Two cases died out of 42 cases of placenta accreta due to catastrophic hemorrhage.

However, neonatal outcomes were comparably equal in both the groups, suggesting that most of the neonatal morbidity is due to iatrogenic prematurity and not placenta accreta per se.

DISCUSSION

CONCLUSION

Placenta accreta is an obstetric emergency, and there is a strong association between placenta previa, placenta accreta, and prior cesarean section. Prenatal diagnosis is essential in planning the delivery to reduce the risk of bleeding and possible complications.

Thus, using PAI score as a predictive score will allow multidisciplinary planning and timely intervention to reduce overall morbidity and mortality associated with abnormally invasive placenta.

CONTRIBUTION TO AUTHORSHIP

Ankita Mathur, Lata Rajoria, and Aditi Bansal contributed to study concept, design, and defining intellectual concept. Literature was searched by Ankita Mathur, Aditi Bansal, and Sunita Hemani. Clinical study and data acquisition were done by Ankita Mathur and Jyotsna Vyas. Statistical analysis was done by Ankita Mathur, Aditi Bansal, and Jyotsna Vyas with the help of statistician. Manuscript preparation and editing were done by Ankita Mathur, Lata Rajoria, and Sunita Hemani.

DETAILS OF ETHICS APPROVAL

This study was approved by Ethical Committee, SMS Medical College, and Attached Hospitals, Jaipur (No. 184/MC/EC/2019), on July 7, 2018.

REFERENCES

1. Hughes EC, ed. Obstetric-gynecologic terminology: with section on neonatology and glossary on congenital anomalies. Philadelphia (PA): F.A. Davis; 1972.

2. Silver RM, Landon MB, Rouse DJ, et al. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstet Gynecol 2006;107(6):1226–1232. DOI: 10.1097/01.AOG.0000219750.79480.84.

3. Daskalakis G, Anastasakis E, Papantoniou N, et al. Emergency obstetric hysterectomy. Acta Obstet Gynecol Scand 2007;86(2):223–227. DOI: 10.1080/00016340601088448.

4. Orbach A, Levy A, Wiznitzer A, et al. Peripartum cesarean hysterectomy: critical analysis of risk factors and trends over the years. J Matern Fetal Neonatal Med 2011;24(3):480–484. DOI: 10.3109/14767058.2010.501128.

5. Sumigama S, Itakura A, Ota T, et al. Placenta previa increta/percreta in Japan: a retrospective study of ultrasound findings, management and clinical course. J Obstet Gynaecol Res 2007;33(5):606–611. DOI: 10.1111/j.1447-0756.2007.00619.x.

6. Eller AG, Porter TF, Soisson P, et al. Optimal management strategies for placenta accreta. BJOG 2009;116(5):648–654. DOI: 10.1111/j.1471-0528.2008.02037.x.

7. Rac MWF, Dashe JS, Wells CE, et al. Ultrasound predictors of placental invasion: the placenta accreta index. Am J Obstet Gynecol 2015;212(3):343.e1–343.e7. DOI: 10.1016/j.ajog.2014.10.022.

8. Samosir SM, Irianti S, Tjahyadi D. Diagnostic tests of placenta accreta index score (PAIS) as supporting prenatal diagnosis and outcomes of maternal neonatal in abnormally invasive placenta management at general hospital of Hasan Sadikin Bandung. Int J Reprod Contracept Obstet Gynecol 2017;6(9):3765–3769. DOI: 10.18203/2320-1770.ijrcog20173666.

9. Nelson T, Chang E, Goodier C, et al. Validation of the placenta accreta index (PAI): improving the antenatal diagnosis of the morbidly adherent placenta. AJOG 2017;216(1):S133–S134. DOI: 10.1016/j.ajog.2016.11.114.

10. Satija B, Kumar S, Wadhwa L, et al. Utility of ultrasound and magnetic resonance imaging in prenatal diagnosis of placenta accreta: a prospective study. Indian J Radiol Imaging 2015;25(4):464–470. DOI: 10.4103/0971-3026.169456.

11. Finberg HJ, Williams JW. Placenta accreta: prospective sonographic diagnosis in patients with placenta previa and prior cesarean section. J Ultrasound Med 1992;11(7):333–343. DOI: 10.7863/jum.1992.11.7.333.