Hai Ho, MD
Department of Family Practice

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

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 lowgrade 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 3637 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

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