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

2. What is placenta previa?
Implantation of placenta over cervical os

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

4. 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.

5. 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

6. 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

7. 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%

8. Fetal complications? Malpresentation
Preterm premature rupture of membrane

9. Diagnostic test?
Ultrasound

10. Placenta Previa: ultrasound
Bladder
Cervix

11. Placenta Previa: ultrasound

12. 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

13. 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)

14. Placenta accreta: ultrasound

15. 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.

16. Velamentous insertion
Vasa Previa
Velamentous insertion

17. Velamentous insertion
Vasa Previa
Velamentous insertion

18. Velamentous insertion
Vasa Previa
Velamentous insertion

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

20. Management of placenta previa?
Individualized based on (not much evidence):
Gestational age
Amount of bleeding
Fetal condition and presentation

21. 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

22. 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

23. 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

24. 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

25. 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 weeks’ gestation

26. 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

27. Placenta Abruption

28. What is placental abruption?
Premature separation of placenta from the uterus

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

30. 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

31. Types of placental abruption
16% 4%
81%

32. Types of placenta hemorrhage

33. 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

34. 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

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

36. 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

37. Ultrasound: subchorionic abruption

38. Ultrasound: retroplacental abruption

39. 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

40. Blood tests? CBC – hemoglobin and platelets Fibrinogen
Normal 450 mg/dL
<150 mg/dL – severe DIC
Fibrin degradation products
PT and PTT

41. 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

42. 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 > mg/dL, and platelets > 60,000/m3
Mode: vaginal vs. Cesarean-section
Tocolysis is contraindicated in severe placental abruption

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

44. The End