Placenta PreviaLiu WeiDepartment of Ob & GyRen Ji hospital

General considerationsDefinition In placenta previa, the placenta is implanted in the lower uterine segment and located over the internal os. It constitutes an obstruction of descent of the presenting part.Main cause of obstetrical hemorrhageIncidence 0.24%-1.57% (our country).

EtiologyUncertainHigh risk factorsmaternal age: >35 yearsmultiparity: 85% - 90%prior cesarean delivery: 5 timessmoking

EtiologyCausesEndometrial abnormalityScared or poorly vascularized endometrium in the corpus.Curettage, Delivery, CS and infection of endometriumPlacental abnormality Large placenta (multiple pregnancy), succenturiate lobe ()Delayed development of trophoblast

ClassificationTotal placenta previaThe internal cervical os is covered completely by placentaPartial placenta previaThe internal os is partially covered by placentaMarginal placenta previaThe edge of the placenta is at the margin of the intenal os.

classification

Manifestation Painless hemorrhageThe most characteristic symptomTime: late pregnancy (after the 28th week) and deliveryCharacteristics: sudden, painless and profuseCause of bleedingMechanical separation of the placenta from its implantation site, either during the formation of the lower uterine segment, during effacement and dilatation of the cervix in labor. Placentitis. Rupture of the venous in the decidua basalis

ManifestationAnemia or shock repeated bleeding anemia heavy bleeding shockAbnormal fetal position a high presenting part breech presentation (often)

DiagnosisHistoryPainless hemorrhageAt late pregnancy or deliveryHistory of curettage or CS

DiagnosisSignsAbdominal findingsUterus is soft, relaxed and nontender. Contraction may be palpated.A high presenting part cant be pressed into the pelvic inlet. Breech presentationFetal heart tones maybe disappear (shock or abruption)

DiagnosisSpeculum examination () Rule out local causes of bleeding, such as cervical erosion or polyp or cancer. Limited vaginal examination (seldom used) Palpation of the vaginal fornices to learn if there is an intervening bogginess between the fornix and presenting part.Rectal examination is useless and dangerous

DiagnosisUltrasonographyThe most useful diagnostic method: 95%Not make the diagnosis at the mid pregnancy. (34 weeks)MRICheck the placenta and membrane after delivery

Differential DiagnosisPlacental abruption vagina bleeding with pain, tenderness of uterus. Vascular previaAbnormality of cervix cervical erosion or polyp or cancer

Effectsobstetrical hemorrhagePlacenta accretaAnemia and infectionPremature labor or fetal death or fetal distress

Treatments Expectant therapyRest: keep the bedControlling the contraction: MgSO4Treatment of anemiaPreventing infection

TreatmentsTermination of pregnancyCStotal placenta previa (36th week), Partial placenta previa (37th week) and heavy bleeding with shockPreventing postpartum hemorrhage: pitocin and PGHysterectomy: Placenta accreta or uncontroled bleeding

TreatmentsVaginal delivery Marginal placenta previa Vaginal bleeding is limited

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