Answer :USMLE step 2 Mcq 20:A woman in her third trimester of pregnancy develops minor vaginal bleeding

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Correct Answer: B
Explanation:
In placenta accreta the placenta forms an abnormally firm attachment to the uterine wall. There is absence of the decidua basalis and incomplete development of the fibrinoid layer. The placenta can be attached directlyto the myometrium (accreta), invade the myometrium (increta), or penetratethe myometrium (percreta). Sonographic criteria used included

(1) loss of the normal hypoechoic retroplacental myometrial zone,
(2) thinning or disruption of the hyperechoic uterine serosa-bladder interface, and
(3) presence of focal exophytic masses.

Placenta accreta is now the most common indication for postcesarean hysterectomy. Approximately 25 percent of patients having a cesarean delivery for placenta previa in the presence of a prior uterine incision subsequently require cesarean hysterectomy for placenta accreta. The risk of placenta accreta appears to increase with the number of prior incisions. This obstetric complication may be increasing in frequency because of the increasing incidence of previous cesarean sections. In patients with previous cesarean delivery who have placenta previa, the incidence of placenta accreta is approximately 10 to 35 percent. In patients with multiple cesarean deliveries and placenta previa the risk of accreta is 60 to 65 percent. At least two thirds of the patients with placenta previa/placenta accreta will require cesarean hysterectomy. However, in cases where uterine preservation is highly desired and no bladder invasion has occurred, bleeding after placental removal has been successfully controlled with a variety of surgical techniques. Complete placenta accreta suspected or confirmed before attempted placental removal may permit other treatment options. Bleeding may be minimal unless the placenta haspartially separated. If no cleavage plane is identified and a placenta accreta is suspected, one should first make preparations for the possibility of major postpartum blood loss. At least 4 units of blood should be on hand and an anesthesiologist present in the delivery room. If vaginal delivery has occurred, the patient should be in a suite in which a laparotomy can be performed, and surgical instruments for hysterectomy should be sterilized and ready.


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