PLACENTA PREVIA Lin Qi De

Definition Placenta previa: Abnormal location of the placenta over ,or in close proximity to the internal os. Incidence: approximately 1 /250 pregnancy 　　　nulliparas: 1/1000~1/1500 pregnancy 　　grandmultiparas: 1/20

Classification Complete (total) placenta previa: entire cervical os is covered Partial placenta previa:the margin of the placenta extends across but not all of the internal os. Marginal:edge of the placenta lies adjacent to the internal os Low lying placenta:placenta is located near but not directly adjacent to the internal os.

Etiology Mechanism: abnormal vascularization Predisposing factors: Twin pregnancy Increasing maternal age Increasing parity Previous cesarean section

diagnosis Painless vaginal bleed: Ultrasonography: first bleeding episode is 29~30 weeks Ultrasonography: benefit in localizing the placenta and diagnosis placenta previa Bleeding is caused by seperation of part of the placenta from the lower uterine segment and cervix,possibly in response to mild uterine contractions. If the placenta lies in the posterior portion of the lower uterine segment,its exact relation with the internal os may be more difficult to ascertain. In these instances,transvaginal ultrasonography is useful adjunct to the transabdominal approach.

Caution Double setup vaginal examination No digital vaginal or rectal examination is preformed in case of placenta previa . Only as a final and definitive event and only under conditions of double set up. This procedure involves careful evaluation of the cervix in the operation room with full preparations for rapid cesarean section. Before the widespread use of ultrasound, this procedure was done more frequently than it is in modern obstetrics.

Management Basic management Initial hospitalization with hemodynamic stabilization Enforced bed rest Restrictions of activity

Expectant management (allow for further fetal growth and maturation) Blood transfusion is given as necessary Amniocentesis for fetal lung maturity testing Cesarean birth if fetus is thought to be mature If the fetus is thought to be mature by gestational age criteria or by amniocentesis for fetal lung maturity testing,there is little benefit to be gained by a delay in delivery. The degree of bleeding and the maturity of the fetus must be constantly weighted in managing these patients.

Indication of vaginal delivery Delivery can be accomplished with minimal blood loss Fetus is dead Major fetal malformation

Complication Placenta previa accreta Postpartum hemopphage Increasing maternal mortality and perinatal mortality