Placenta Previa

Hai Ho, MD Department of Family Practice

What is placenta previa?

Implantation of placenta over cervical os

Types of placenta previa

Who are at risk for placenta previa?

 Endometrial scarring of upper segment of uterus – implantation in lower uterine segment  Prior D&C or C-section  Multiparity  Advance age – independent risk factor vs. multiparity

Who are at risk for placenta previa?

 Reduction in uteroplacental oxygen or nutrient delivery – compensation by increasing placental surface area  Male  High altitude  Maternal smoking

Factors that determine persistence of placenta previa?

 Time of diagnosis or onset of symptoms  Location of placenta previa

Repeat ultrasound at 24 – 28 weeks’ gestation

Clinical presentations?

 Painless vaginal bleeding – 70-80%  1/3 prior to 30 weeks  Mostly during third trimester – shearing force from lower uterine segment growth and cervical dilation  Sexual intercourse  Uterine contraction – 10-20%

Fetal complications?

 Malpresentation  Preterm premature rupture of membrane

Diagnostic test?

Ultrasound

Placenta Previa: ultrasound Placenta

Placenta Previa: ultrasound

Placenta accreta?

 Abnormal attachment of the placenta to the uterine wall (decidua) such that the chorionic villi invade abnormally into the myometrium  Primary deficiency of or secondary loss of decidual elements (decidua basalis)  Associated with placenta previa in 5-10% of the case  Proportional to the number of prior Cesarean sections

Variations of placenta accreta

Placenta accreta: ultrasound

Vasa Previa?

Vasa Previa

Vasa Previa

Vasa Previa

Vasa Previa    Rupture Compression of vessels Perinatal mortality rate – 50 – 75%

Management of placenta previa?

Individualized based on (not much evidence):  Gestational age  Amount of bleeding  Fetal condition and presentation

Preterm with minimal or resolved bleeding  Expectant management – bed rest with bathroom privilege  Periodic maternal hematocrit  Prophylactic transfusion to maintain hematocrit > 30% only with continuous low grade bleeding with falling hematocrit unresponsive to iron therapy

Preterm with minimal or resolved bleeding  Fetal heart rate monitoring only with active bleeding  Ultrasound every 3 weeks – fetal growth, AFI, placenta location  Rhogam for RhD-negative mother

Preterm with minimal or resolved bleeding  Amniocentesis weekly starting at 36 weeks to assess lung maturity – delivered when lungs reach maturity  Betamethasone or dexamethasone between 24 – 34 weeks’ gestation to enhance lung maturity  Tocolysis – magnesium sulfate

Active bleeding  Stabilize mother hemodynamically  Deliver by Cesarean section  Rhogam in Rh-negative mother  Betamethasone or dexamethasone between 24 – 34 weeks’ gestation to enhance lung maturity

Management of placenta previa  No large clinical trials for the recommendations  Consider hospitalization in third-trimester  Antepartum fetal surveillance  Corticosteroid for lung maturity  Delivery at 36 37 weeks’ gestation

Management of placenta accreta  Cesarean hysterectomy  Uterine conservation  Placental removal and oversewing uterine defect  Localized resection and uterine repair  Leaving the placenta in situ and treat with antibiotics and removing it later

Placenta Abruption

What is placental abruption?

Premature separation of placenta from the uterus

Epidemiology  Incident 1 in 86 to 1 in 206 births  One-third of all antepartum bleeding

Pathogenesis  Maternal vascular disruption in decidua basalis  Acute versus chronic

Types of placental abruption 16% 81% 4%

Types of placenta hemorrhage

Risk factors for placental abruption?

 Maternal hypertension  Maternal age and parity – conflicting data  Blunt trauma – motor vehicle accident and maternal battering  Tobacco smoking and cocaine

Risk factors for placental abruption  Prior history of placental abruption  5-15% recurrence  After 2 consecutive abruptions, 25% recurrence  Sudden decompression of uterus in polyhydramnios or multiple gestation (after first twin delivery) – rare  Thrombophilia such as factor V Leiden mutation

Clinical presentations?

 ± Vaginal bleeding  Uterine contraction or tetany and pain  Abdominal pain  DIC  10-20% of placental abruption  Associated with fetal demise  Fetal compromise

Diagnostic test?

 Ultrasound  Sensitivity ~ 50%  Miss in acute phase because blood could be isoechoic compared to placenta  Hematoma resolution – hypoechoic in 1 week and sonolucent in 2 weeks  Blood tests

Ultrasound: subchorionic abruption

Ultrasound: retroplacental abruption

Ultrasound: retroplacental abruption

Blood tests?

 CBC – hemoglobin and platelets  Fibrinogen  Normal 450 mg/dL  <150 mg/dL – severe DIC  Fibrin degradation products  PT and PTT

Management?

 Hemodynamic monitoring  Urine output with Foley  BP drop – late stage, 2-3 liter of blood loss  Fetal monitoring

Management: delivery  Timing  Severity of placental abruption  Fetal maturity - consider tocolysis with MgSO 4 and corticosteroid (24-34 weeks)  Correction of DIC with transfusion of PRBC, FFP, platelets to maintain hematocrit > 25%, fibrinogen >150-200 mg/dL, and platelets > 60,000/m 3  Mode: vaginal vs. Cesarean-section

Couvelaire uterus?

 Bleeding into myometrium leading to uterine atony and hemorrhage  Treatment  Most respond to oxytocin and methergine  Hysterectomy for uncontrolled bleeding