Hai Ho, MD Department of Family Practice Placenta Previa Hai Ho, MD Department of Family Practice

What is placenta previa? Implantation of placenta over cervical os

Types of placenta previa Low-lying – placenta is within 2- 3 cm of the cervical os.

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 Risk of placenta previa is proportional to the number of prior C-section.

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 Placental Migration Progressive growth of placenta toward the fundus and growth of lower uterine segment from 0.5 cm at 20 weeks to 5 cm at term. 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 Bladder Cervix

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 - chorionic villi in contact with myometrium (80% of cases) Placenta Increta - chorionic villi invade into myometrium (15% of cases) Placenta Percreta - chorionic villi invade into serosa (5% of cases)

Placenta accreta: ultrasound

Vasa Previa? Normally, the veins of the baby run from the middle of the placenta via the umbilical cord to the baby. Velamentous insertion means that the veins, unprotected by Wharton's jelly, traverse the membranes before they come together into the umbilical cord.  The umbilical cord inserts on the placental mass in about 99% of cases. The insertion site may vary from the center of the fetal surface to the border of the placenta. The term velamentous insertion is used to describe the condition in which the umbilical cord inserts on the chorioamniotic membranes rather than on the placental mass. Therefore, a variable segment of the umbilical vessels runs between the amnion and the chorion, losing the protection of the Wharton's jelly.

Velamentous insertion Vasa Previa Velamentous insertion

Velamentous insertion Vasa Previa Velamentous insertion

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 It is not clear whether abruption results from a single pathologic event or the culmination of a long-standing fetal-placental interface disorder. In some cases, such as catastrophic trauma, a single precipitating event (eg, motor vehicle accident or fall) likely caused the outcome. However, a single precipitating event is not evident in the majority of pregnancies with abruptio placentae. A chronic pathological process at the fetal-placental interface is likely in these pregnancies with abruption as the culmination of a long chain of events. Several studies have demonstrated a higher incidence of fetal growth disorders and preterm birth in pregnancies ending in abruption

Types of placental abruption 16% 4% 81%

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 Should look for physical abuse. Bleeding after trauma is usually within 24 hours. antihypertensive therapy does not appear to reduce the risk of abruption among women with chronic hypertension

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 Should look for physical abuse. Bleeding after trauma is usually within 24 hours. antihypertensive therapy does not appear to reduce the risk of abruption among women with chronic hypertension

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 Blood tests 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 A, Ultrasound study at 18 weeks' gestation demonstrating a hypoechoic area (A) representing retroplacental bleeding and an enlarged placenta (P). This patient had chronic hypertension. She presented with intermittent dark red vaginal bleeding and abdominal pain, a picture consistent with a chronic abruption. B, At delivery, the placenta revealed a large clot (small arrow) and fresh hemorrhage (large arrow). The fibrous bands bridging the clot are also consistent with chronic 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 Fetal monitoring Urine output with Foley BP drop – late stage, 2-3 liter of blood loss Fetal monitoring Tocolysis is contraindicated in severe placental abruption

Management: delivery Timing Mode: vaginal vs. Cesarean-section 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 Tocolysis is contraindicated in severe placental abruption

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

The End