Two Dimensional and Color Doppler Ultrasound Scoring in Evaluation of Anterior Low Lying Placenta and its Adherence to Previous One Cesarean Section Scar inthe Third Trimester

INTRODUCTION

Morbidly adherent placentas are characterized by a range of abnormalities, including placental myometrium invasion as well as invasion past the myometrium and muscle layers into adjacent structures. This condition has lately become increasingly common due to an increase in the frequency of cesarean deliveries, and it is classified into three classes depending on histopathology ¹.

           Placenta accreta's exact pathogenesis is unknown. A number of theories have been offered, including decidua maldevelopment, excess trophoblastic invasion, or a mix of the two ². Deficient decidualization, abnormal maternal vascular remodeling, excess trophoblastic invasion, or combinations of these are thought to be the result of prior instrumentation ³.

Placenta accreta is a serious pregnancy complication which can result in extensive and potentially life-threatening intrapartum and postpartum bleeding ⁴. Placenta accreta has been the main reason for urgent hysterectomy due to severe uterine bleeding, which could necessitate extensive life-saving surgical treatments like hysterectomy and ligation of major pelvic vessels ⁴.

As a result of placental invasion into nearby organs, repair of the urinary bladder or bowel might be required. In these drastic instances, massive transfusions of blood and blood products are the rule. Other complications include neonatal death, infection, fistula formation & ureteral damage ⁵.

Maternal morbidity and mortality have been documented in up to 60% and 7% of women with placenta accreta, respectively. Furthermore, the frequency of perinatal complications has grown, owing primarily to preterm delivery and fetuses that are undersized for gestational age ⁶.

A prior cesarean birth, especially when combined with a coexisting placenta previa, has been identified as a risk factor for placenta accreta. The risk of placenta accreta increases exponentially as the number of past cesarean births increases ⁷. Other predisposing factors have been identified including: scarred uterus, multiple pregnancies, prior uterine operations, advanced mother age, and prior uterine curettage ^{5, 8}.

The best time to diagnose placenta accreta is during the antenatal stage, using sonographic or magnetic resonance imaging methods. Much research has shown that ultrasonography can be used to make this diagnosis, especially at 9. Regrettably, some instances of placenta accreta are detected during birth when the woman suffers from persistent vaginal hemorrhage or severe vaginal hemorrhage when the placenta is attempted to be removed, or merely a portion of the placenta may be removed ¹⁰.

The study aimed to assess the accuracy of each 2D & color Doppler flow in the placenta accrete diagnosis and to postulate a scoring system based on 2D and color Doppler flow criteria to predict placental invasion in women who have had at least one cesarean section in the 3^rd trimester.

PATIENTS AND METHODS

Type and Duration of the study: The study is a prospective cohort study that includes all cases diagnosed with placenta previa anterior plus one previous cesarean section who were admitted to Al Hussein and Sayed Galal University Hospital between January and December 2020. The study has been accepted by the obstetric department's ethical committee, and after proper counseling, all 107 women solicited for enrollment in the obstetric department and provided written informed consent.

Inclusion criteria include: Diagnosis: patients must have placenta previa anterior (anterior wall low lying). Gestational age: more than 30 weeks at the beginning of the research. Parity: patients must have one previous cesarean section.

Exclusion criteria: Patients with unscared uterus, or scared uterus other than cesarean section or more than one cesarean section. Patients who have a normally positioned placenta. Placenta previa posterior. Coagulopathy or other co-morbidity

Diagnosis of placenta previa: Diagnostic criteria suspecte of placenta accreta

Ultrasound is the suggested initial step in diagnosing placenta previa accrete ¹⁾.

Table (1): Ultrasound criteria that diagnosis of morbidly adherent placenta.  

Color Doppler ultrasound was recommended to assist in the placenta previa accreta diagnosis since it displays abnormal regions of hypervascularity with dilated blood vessels inside the placenta and uterine tissues ^{12, 1}.

Table (2): Color Doppler criteria that diagnosis of morbidly adherent placenta

Preoperative Preparation

Preoperative procedures are designed to improve the outcome, decrease the risk of complications and make the surgical approach of placenta accreta as safe as possible, these preparations include: Complete laboratory tests: a full blood count, hepatic function tests , kidney function tests, and coagulation profile. If anemia is discovered, it must be corrected properly before delivery by blood transfusion if Hemoglobin level is below 9 gm/dl or the the fetus is more than 36 weeks gestation. Anemia may be corrected by parentral iron if Hemoglobin level is above 9 gm/dl or the fetus is less than 36weeks gestation. Proper counselling of the patient and her relatives about her case and possible complications as cesarean hysterectomy, bladder, intestinal injury up to death. Patients and her relatives must sign an informed consent form acknowledging that they are aware of risk and complications. The surgery will not proceed unless the consent form is signed. Preparing of cross matched blood of the same blood group at least two bags of blood and four units of fresh frozen plasma and must be available before surgery. Preparing of Intensive Care Unit (ICU) bed before the operation as some patients need ICU admission after delivery.

Outcomes:

Primary outcome criteria: During the 2nd cesarean section, placental accretion was discovered intraoperatively. (time frame): intra-operative during cesarean section

Secondary outcome criteria:  Uterin conservation versus to cesarean hysterectomy. (time frame: intra-operative during cesarean section

Postpartum bleeding (time frame: from fetus birth to 24 hours following fetus birth) quantity of postpartum hemorrhage is > 1000 ml. Severe postpartum bleeding (time frame: from fetus birth to 24 hours following fetus birth) quantity of postpartum hemorrhage was > 1500 ml. Injury to the bladder (time frame: intra-operative) (during the cesarean birth time) Bladder injury as a result of the birth of the placenta or hemorrhage control.

Statistical analysis:

P-value: is the likelihood that the null hypothesis will be rejected (Ho). If the P-value is less than the chosen significance level then the null hypothesis (Ho) is rejected. The choice of significance level at which the Ho is rejected is arbitrary. Traditionally the 5, 1.5 & 0.1% (p˂0.05, 0.01, 0.001) regions are used.

P: The probability/significance value: P value greater than 0.05 (NS) It's insignificant.* Significant at the 0.05 level when the P value is less than 0.05. ** Significant at 0.01 level when P value is less than 0.01.

Binary logistic regression: This technique has been utilized to predict the result of a categorical parameter depending on one or more predictive factors. Receiver operating characteristic (ROC curve) analysis has been done to determine the total predictivity of the parameter and the optimal cut-off value, as well as the specificity and sensitivity at this cut-off value.

Sensitivity, Specificity and Predictive value of Ultrasound and Doppler: Color Doppler imaging has high specificity and sensitivity for identifying placenta previa accreta, particularly anterior placenta accreta, since abnormal uteroplacental invasion might be observed with high confidence. Ultrasonography and Doppler were suggestive of morbid adherence in 38 instances (95.2%) of patients approved by placenta accreta, with an accuracy of 96 %, specificity of 97.3%, sensitivity of 95.24%, PPV of 98.36%, and NPV of 92.31%.

RESULTS

Table 3: True positive & negative and false positive & negative of US and color Doppler compared to surgical intervention used as the “Gold Standard”.

Table 4: Sensitivity and specificity and Accuracy and Positive value and Negative value.

Table (5): Multivariate regression analysis for prediction of placenta accreta using two dimensional and color Doppler ultrasound compared to surgical intervention used as the “Gold Standard”.

Using: Mann-Whitney z-test; **p-value

Table (6): Comparison between absent outcome and present outcome according to total score of finding through US & Color Doppler.

Fig. 1: The total Score of Finding through US & Color Doppler was used to create a Receiver-operating characteristic (ROC) curve for predicting placental accreta.

Table 7: The total Score of Finding through US & Color Doppler was used to create a Receiver-operating characteristic (ROC) curve for predicting placental accreta.

The optimal cut off value of the total score was ≥ 55, with sensitivity of 95.5 %, specificity of 92.5 %, PPV of 95.5 %, NPV of 92.5 %, and diagnostic accuracy of 94.3 % using the (ROC) curve.

Quantitative results were divided into quartile range of less than or equal to 25th percentile, 25-75th percentile and >75th percentile, accordingly, they are divided into 3 levels

The level of probability is divided into three levels; Less probability of placental accreta at cut-off score (≤37); Mild to moderate probability of placental accreta at cut-off score (>37-<55) and High probability of placental accreta at cut-off score (≥55).