Placenta accreta

• Placenta previa is defined as a placenta located over the cervical os.

There are 3 major types.

Complete previa describes a placenta that completely covers the cervical os.

Partial previa is a placenta that covers some of the cervical os, with the remainder of the os uncovered by the placenta.

Marginal previa describes a placenta that is located at the edge of the cervical os.

Three major risk factors for placenta previa are maternal age, minority race, and previous cesarean delivery.

• Placenta accreta describes the condition in which there is abnormal attachment of the placenta to the uterine wall.

In this condition, the decidua basalis is absent and the placenta is attached to the myometrium(accreta) or invades into the myometrium (increta) or perforates through the myometrium (percreta).  

Many patients with a previa and accreta will require a hysterectomy at the time of delivery. This patient, with a history of 2 prior cesarean deliveries and a placenta previa is at highest risk for placenta accreta.

• This patient would not be considered to be at highest risk of dystocia (Choice A) because, with a placenta previa, she would not be allowed to labor and, therefore, would not be at risk of dystocia

Ans:A.)Placenta accreta 

 Breech Presentation

The following are the known factors responsible for breech presentation:

•  Prematurity: It is the most common cause of breech presentation.
•  Factors preventing spontaneous version: (a) Breech with extended legs, (b) Twins, (c) Oligohydramnios, (d) Congenital malformation of the uterus such as septate or bicornuate uterus, (e) Short cord, relative or absolute, (f ) Intrauterine death of the fetus.
•  Favorable adaptation: (a) Hydrocephalus—big head can be well accommodated in the wide fundus, (b) Placenta previa, (c) Contracted pelvis, (d) Cornu-fundal attachment of the placenta— minimizes the space of the fundus where the smaller head can be placed comfortably.
•  Undue mobility of the fetus: (a) Hydramnios, (b) Multiparae with lax abdominal wall.
•  Fetal abnormality: Trisomies 13, 18, 21, anencephaly and myotonic dystrophy due to alteration of fetal muscular tone and mobility.

Placenta accreta

• It occurs when all or part of the placenta attaches abnormally to the myometrium (the muscular layer of the uterine wall). Three grades of abnormal placental attachment are defined according to the depth of attachment and invasion into the muscular layers of the uterus:
  • Accreta – chorionic villi attach to the myometrium, rather than being restricted within the decidua basalis.
  • Increta – chorionic villi invade into the myometrium.
  • Percreta – chorionic villi invade through the perimetrium (uterine serosa).
• Complications:
  • (i) damage to local organs (e.g., bowel, bladder, ureters) and neurovascular structures in the retroperitoneum and lateral pelvic sidewalls from placental implantation and its removal; (ii) postoperative bleeding requiring repeated surgery; (iii) amniotic fluid embolism; (iv) complications (e.g., dilutional coagulopathy, consumptive coagulopathy, acute transfusion reactions, transfusion-associated lung injury, acute respiratory distress syndrome, and electrolyte abnormalities) from transfusion of large volumes of blood products, crystalloid, and other volume expanders; and (v) postoperative thromboembolism, infection, multisystem organ failure, and maternal death.

Ref: Textbook of Obstetrics By Dutta

Placenta increta

Hysterectomy

Ans. is a i.e. Seen in cesarean scar

Ans. is d i.e. Previous placenta previa / abruptio placenta

Ans. :D.)All of the above: a, b and c i.e. Placenta previa; Uterine scar and Multipara.

Placenta accreta

• It is a type of morbidly adherent placenta, where the placenta is firmly adherent to the uterine wall due to partial or total absence of the decidua basalis and the fibrinoid layer (Nitabuch layer). The main aetiology is defective decidua formation.

Pathological findings

• Absence of decidua basalis
• Absence of Nitabuch’s fibrinoid layer
• Varying degree of penetration of the villi into the muscle bundle.

Classification / variants :

• Placenta accreta – chorionic villi are attached to the superficial myometrium.
• Placenta increta – villi invade the myometrium.
• Placenta percreta – villi penetrate the full thickness myometrium up to the serosal layer.

Risk factors:

• An important risk factor for placenta accreta is placenta previa in the presence of a uterine scar.
• Additional reported risk factors for placenta accreta include maternal age and multiparity, other prior uterine surgery, prior uterine curettage, uterine irradiation, endometrial ablation, Asherman syndrome, uterine leiomyomata, uterine anomalies, hypertensive disorders of pregnancy, and smoking.
• Other risk factors include low-lying placenta, anterior placenta, congenital or acquired uterine defects (such as uterine septa), leiomyoma, ectopic implantation of placenta (including cornual pregnancy).
• Pregnant people above 35 years of age who have had a Caesarian section and now have a placenta previa overlying the uterine scar have a 40% chance of placenta accreta

Prior to delivery : presumptive diagnosis made by

• Transvaginal sonography – absence of the subplacental sonoluscent zone(which represents the normal decidua basalis) indicates a placenta accrete.
• Doppler imaging
• MRI

Complications:

• Antepartum haemorrhage (due to associated placenta previa)
• Uterine rupture before labour (due to myometrial invasion by placental villia at the site of previous C- section scar.
• Postpartum haemorrhage
• Infection
• Inversion of uterus (rare).

Management

Atonic uterus

Ans. C i.e. Vasa previa