Replies to This Discussion

Permalink Reply by Dr.Shagufta Liaqat on June 20, 2011 at 2:24pm

Hi zenab,

              Placenta previa can be diagnosed by pelvic ultrasound trans abdominally but for good visualization of placental localization, we can do transvaginal ultrasound as it is safe and has excellent resolution to show the proximity of placenta with respect to internal os of vagina.

Placenta accreta can be diagnosed by doppler scan when we are suspicious by the history of patient. In this case placetal tissue as well as placental blood vessels are seen to traverse the myometrium. 

Permalink Reply by Syed Amir Gilani on September 16, 2011 at 11:13am

placenta previa and placenta accreta are two different conditions,here are details

Differential Diagnosis

The differential includes:

• Placenta previa with normal placental attachment
• Placenta previa with placenta accreta
• Placenta previa with placenta increta
• Placenta previa with placenta percreta

 

Diagnosis

Placenta previa and Placenta accreta

 

Discussion

Placenta previa is a condition in which placental tissue covers the cervix. Types include:

 

Marginal or Partial - Placenta covers part of the cervix without completely covering the internal os

Complete - Placenta completely covers the cervical os

The incidence of placenta previa is about 1 in 200 pregnancies and increases with prior cesarean section, advanced maternal age and multiparity.

Translabial (transperineal) or transvaginal scanning may be helpful for better visualization of the lower uterine segment and cervix, when transabdominal findings are inconclusive.

Placenta accreta is abnormal attachment of the placenta to the uterine wall (decidua) such that the chorionic villi invade abnormally into the myometrium. It is thought to result from either a primary deficiency of or secondary loss of decidual elements (decidua basalis). Three grades are used, based on pathologic assessment of myometrial invasion by the chorionic villi:

 

1. Placenta Accreta - chorionic villi in contact with myometrium (80% of cases)
2. Placenta Increta - chorionic villi invade into myometrium (15% of cases)
3. Placenta Percreta - chorionic villi invade into serosa (5% of cases)

All three forms of abnormal placentation are associated with a history of prior cesarean section, history of uterine instrumentation or surgery, or placenta previa. Rarely, abnormal attachment is seen in the absence of prior surgery and in the absence of placenta previa.

Sonographic findings include:

• loss of the normal hypoechoic rim of myometrial tissue beneath the placenta
• loss of the normal hyperechoic uterine serosa-bladder wall interface
• presence of tissue of placental echotexture extending beyond the uterine serosa.

An associated finding that is sometimes seen is multiple or large placental venous lakes.

 

 

References

1. Finberg HJ, Williams JW. Placenta Accreta. Prospective sonographic diagnosis in patients with placenta previa and prior cesarean section. J Ultrasound Med 11:333-343, 1992.

2. Hertzberg B, Bowie J, Carroll B, Kliewer M, Weber T, et al. Diagnosis of placenta previa during the third trimester: Role of transperineal sonography. AJR 159:83-87, 1992.

3. Hoffman-Tretin J, Koenigsberg M, Rabin A, Anyaegbunam A. Placenta Accreta: Additional sonographic observations. J Ultrasound Med 11:29-34, 1992.

4. Townsend R. Ultrasound evaluation of the placenta and umbilical cord. In: Callen Peter, editor. Ultrasonography in obstetrics and gynecology. Philadelphia: Saunders, 1994: 445-53.