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
Velamentous insertion
Vasa Previa
Velamentous insertion
Vasa Previa
Velamentous insertion
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 MgSO4
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/m3
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