Obstetrics Book


Placenta Previa

Aka: Placenta Previa
  1. See also
    1. Late Pregnancy Bleeding
  2. Epidemiology
    1. Incidence
      1. Most common cause of Third Trimester Bleeding
      2. Second trimester (16-20 weeks): 5%
      3. Term: 0.5% (90% of low placentas resolve by term)
  3. Definition
    1. Low Implantation of placenta within 2 cm of internal os
    2. Placenta lies alongside or in front of presenting part
  4. Types
    1. Type 1: Low Implantation
      1. Lower placenta margin dips into lower uterine segment
      2. Edge lies within 2 to 3.5 cm of internal cervical os
    2. Type 2: Marginal Placenta
      1. Placenta within 2 cm of internal os, does not cover
    3. Type 3: Partial Previa
      1. Placenta covers internal os when closed
      2. Placenta does not cover os when fully dilated
    4. Type 4: Complete Previa (Central Previa)
      1. Placenta covers internal os even when fully dilated
  5. Pathophysiology
    1. Placenta usually implants at fundus
      1. Fundal blood supply is better than lower Uterus
    2. Abnormal implantat occurs at uterine scar or disruption
  6. Risk factors
    1. Previous Cesarean Section or uterine curettage
      1. Associated with placenta accreta
    2. High Parity or Multiple Gestations
    3. Older maternal age
    4. Chronic Hypertension
    5. Multiple Gestation
    6. Tobacco Abuse
    7. Preterm Labor
    8. Previous uterine instrumentation
  7. Associated Conditions
    1. Abnormal presentation (placenta raises presenting part)
      1. Oblique Lie
      2. Transverse Lie
    2. Placental Abruption
    3. Intrauterine Growth Retardation
    4. Placenta accreta (especially if prior ceserean section)
    5. Antepartum bleeding
    6. Postpartum Hemorrhage
    7. Preterm delivery
  8. Symptoms
    1. Painless uterine bleeding after 18-20 weeks gestation
      1. Typically occurs at 27-32 weeks: "Sentinel bleed"
      2. May be provoked with intercourse, contractions
    2. Abdomen soft and non-tender
  9. Exam
    1. Avoid digital vaginal exam or speculum exam if suspected Placenta Previa
  10. Labs
    1. See Late Pregnancy Bleeding
    2. Complete Blood Count
    3. Blood Type and Screen
      1. Type and cross match for 2-4 units
    4. Coagulation studies (PT/INR, PTT)
    5. Fibrinogen
      1. Fibrinogen <300 mg/dl may suggest DIC
    6. Kleihauer-Betke Test
    7. Preterm Labor Management
      1. Consider Corticosteroids
      2. Consider Magnesium Sulfate
  11. Differential Diagnosis
    1. Late Pregnancy Bleeding
  12. Imaging: Serial obstetric Transvaginal Ultrasound
    1. Transvaginal Ultrasound is safe and preferred option
      1. Transabdominal Ultrasound lacks adequate precision
      2. Transvaginal changes diagnosis in one in four cases
    2. General evaluation
      1. Interval Fetal Growth
      2. Evaluate for resolution or partial previa
        1. Overlap <1.5 cm over os at 20 wks: Usually resolves
        2. Overlap >2.5 cm over os at 20 wks: Usually persists
        3. Placenta is unlikely to clear cervical os at term if bulk of placenta is over the os at 24 weeks or later
        4. References
          1. Taipale (1998) Ultrasound Obstet Gynecol 12:422-5 [PubMed]
      3. Evaluate for placenta acreta if prior ceserean
    3. Visualization aids
      1. Anterior Placenta Previa
        1. View placental edge with full, then empty Bladder
      2. Posterior Placenta Previa
        1. Transducer lateral and angled toward midline
        2. Consider slight trendelenberg position
        3. Consider gentle Transvaginal Ultrasound
          1. Insert probe only partially into vagina
  13. Management: Counseling
    1. Risk of severe life-threatening Hemorrhage
      1. Risk of fetal death
      2. Risk of maternal death
    2. Blood Transfusion may be necessary
    3. Hysterectomy may be needed to control bleeding
  14. Management: Protocol
    1. Late Pregnancy Bleeding
      1. Ceserean delivery indications
        1. 37 weeks or
        2. Unstable
          1. Heavy uterine bleeding
          2. Hypotension
          3. Fetal Distress (e.g. non-reassuring fetal tracing)
      2. Observation protocol
        1. Hospital observation
          1. Limited bleeding that has resolved at <24 weeks gestation may have close interval follow-up
        2. Follow serial Hemoglobins
        3. Type and cross in preparation for transfusion
        4. Administer Corticosteroids if gestation <34 weeks
          1. See Preterm Labor Management
    2. No bleeding
      1. Ceserean delivery after 36 weeks
        1. Assess for Fetal Lung Maturity with Amniocentesis
      2. Pelvic rest until 36 weeks
      3. Cervical cerclage may be considered
        1. Cobo (1998) Am J Obstet Gynecol 179:122-5 [PubMed]
      4. Follow serial Transvaginal Ultrasounds
        1. Ultrasound at 28-30 weeks
        2. Ultrasound at 36 weeks
  15. Management: General
    1. See also Late Pregnancy Bleeding
    2. Pelvic rest
      1. No sexual intercourse
      2. Avoid digital cervical exam
      3. Gentle speculum exam is permitted (insert 90 degrees)
    3. Cesarean Section at tertiary care center recommended
      1. Delay delivery until mature lung studies if possible
      2. Tocolysis with Magnesium Sulfate is safe
      3. Regional (spinal) Anesthesia preferred over general
        1. General Anesthesia may increase bleeding risk
      4. Marginal previa may allow Vaginal Delivery
        1. Evaluation by experienced clinician only
        2. Double set-up is mandatory for vaginal exam
        3. NSVD indications
          1. Head engaged: Can tamponade marginal previa and
          2. No brisk bleeding on exam and
          3. Close monitoring and
          4. In-house OR team for stat Ceserean
    4. Bleeding management
      1. See Late Pregnancy Bleeding
      2. Placenta Previa with active bleeding is an emergency
        1. See Hemorrhagic Shock
        2. Fluid Resuscitation and Blood Transfusion as needed
        3. Emergent obstetric Consultation
        4. Intensive monitoring of Vital Signs including Blood Pressure
        5. Urine catheter for Urine Output monitoring
        6. Quantify blood loss
  16. References
    1. Bavolek and Mason in Herbert (2018) EM:Rap 18(10): 15-6
    2. Lall (2017) Crit Dec Emerg Med 31(1): 3-9
    3. Bhide (2004) Curr Opin Obstet Gynecol 16:447-51 [PubMed]
    4. Sakornbut (2007) Am Fam Physician 75:1199-206 [PubMed]

Placenta Previa (C0032046)

Definition (SNOMEDCT_US) A condition in which the placenta is located over or near the internal os of the cervix, increasing the risk of hemorrhage.
Definition (SCTSPA) Trastorno en el cual la placenta está ubicada sobre o en la proximidad del orificio interno del cuello uterino, con aumento del riesgo de hemorragia.
Definition (NCI) A condition in which the placenta covers or is within 1 cm of the cervical os.(NICHD)
Definition (MSH) Abnormal placentation in which the PLACENTA implants in the lower segment of the UTERUS (the zone of dilation) and may cover part or all of the opening of the CERVIX. It is often associated with serious antepartum bleeding and PREMATURE LABOR.
Concepts Pathologic Function (T046)
MSH D010923
ICD10 O44
SnomedCT 157059004, 198930005, 36813001
French PLACENTA PRAEVIA, Placenta praevia, Placenta previa
Portuguese PLACENTA PREVIA, Placenta prévia, Placenta Prévia
Swedish Placenta previa
English PLACENTA PRAEVIA, placenta previa (diagnosis), placenta previa, placenta previa was observed, placenta previa (physical finding), Placenta Previa [Disease/Finding], previa placenta, placenta praevia, Placenta praevia (disorder), Placenta praevia, Placenta previa, PP - Placenta praevia, PP - Placenta previa, Placenta previa (disorder), placenta; previa, previa; placenta, Placenta previa, NOS, Placenta Praevia, Placenta Previa
Japanese ゼンチタイバン, 前置胎盤, 胎盤-前置
Czech placenta praevia, Placenta praevia
Finnish Etisistukka
Italian Placenta praevia, Placenta previa
Korean 전치 태반
Polish Łożysko przodujące
Hungarian Elölfekvő lepény, Placenta praevia
Norwegian Placenta praevia, Forliggende morkake
Dutch placenta; praevia, praevia; placenta, placenta praevia, Placenta praevia
Spanish placenta previa (trastorno), placenta previa, Placenta previa, Placenta Previa
German Plazenta praevia, Placenta praevia
Derived from the NIH UMLS (Unified Medical Language System)

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