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