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Female Reproductive System ORGAN SYSTEMS

Placenta previa

Implantation of placenta near the internal os.

Implantation of placenta near the internal os.

Etiology

Risk factors:

  • Defective endometrial vasculature & scarring (leading to compensatory placental hypertrophy):
    • Advancing maternal age
    • Multiparity
    • Previous LSCS
    • Maternal cigarette smoking
  • Big placenta:
    • Multiple pregnancies
    • Placenta succenturiata
    • Placenta membranacea (compensatory mechanism in anaemia)
  • Defective uterine development:
    • Uterine anomalies
  • Idiopathic:
    • Fetal malpresentation
    • Maternal serum-AFP

Classification

Placental previa classification
Yeeles, H., & Jha, S. (2016). Antepartum haemorrhage. In D. Anumba & S. Jivraj (Eds.), Antenatal Disorders for the MRCOG and Beyond (pp. 13-26). Cambridge: Cambridge University Press. doi:10.1017/CBO9781107585799.003

Minor degree:

  • Type I: Low-lying placenta
    • Lower placental margin within 2 cm of internal os
  • Type II: Marginal placenta previa
    • Anterior

Major degree:

  • Type II: Marginal placenta previa
    • Posterior “Dangerous placenta previa”
      • Due to underlying sacral promontory
  • Type III: Partial placenta praevia
    • Lower placental edge covers internal os
  • Type IV: Central placenta praevia “Complete placena praevia”
    • M/dangerous

Presentation

Painless, recurrent vaginal bleeding

Only symptom
  • Sentinel bleed: Warning haemorrhage that first occurs in late 2nd or 3rd trimester
  • Stallworthy sign: Slowing of fetal heart rate on pressing the head down into the pelvis and prompt recovery on release of pressure (d/t posterior placenta previa)
Placenta previa

Complications

Maternal complications:

  • Antepartum complications:
    • Antepartum haemorrhage (APH)
    • Malpresentation
    • Preterm labour
    • Associated abruptio (10% cases)
  • Complications during labour:
    • Cord prolapse
    • Intrapartum haemorrhage
    • Premature rupture of membranes (PROM)
  • Postpartum complications:
    • Postpartum haemorrhage (PPH)
    • Retained placenta
  • Puerperal complications:
    • Puerperal sepsis

Fetal complications:

  • Low birthweight (M/C complication, 15% cases)
  • Birth asphyxia
  • Respiratory distress syndrome
  • Birth injuries
  • Congenital malformations (3x risk)

Diagnosis

Lab investigations:

  • Haemoglobin, hematocrit
  • ABO/Rh typing
  • Coagulation studies
    • Bleeding time, PT, APTT, etc
  • Renal function test (RFT)
    • Urine output
    • Urea
    • Creatinine

Fetal surveillance tests:

  • Fetal movement counts
  • Non-stress test (NST)
  • Biophysical profile score

Imaging:

  • USG ± Doppler
    • 18-22 weeks (repeat after 2 months if low lying placenta seen)
  • MRI
    • Reserved for placenta praevia accreta
Fluoroscopic findings placenta previa
Fluoroscopic findings, confirming the placement of the occlusion balloon catheters in both internal iliac arteries (arrow: contrast material injected into the left internal iliac artery) | Yamaguchi M, Yoshida K, Takano T, Enomoto T, Takakuwa K. Placenta previa and percreta with massive genital bleeding in the first trimester of pregnancy: A case report. 2017.
Ultrasonogram placental previa
Ultrasonogram at the 11th week of gestation, showing intraplacental lacunae (arrowheads) | Yamaguchi M, Yoshida K, Takano T, Enomoto T, Takakuwa K. Placenta previa and percreta with massive genital bleeding in the first trimester of pregnancy: A case report. 2017.

Differential diagnosis:

  • Accidental hemorrhage “Abruptio placentae”
  • Placenta accreta

Management

Mcafee and Johnson regimen:

Expectant management preferred before term which aims to continue pregnancy for fetal maturity without compromising maternal health
  • Continue pregnancy till 37 weeks
  • Avoid cervical stimulation
    • No vaginal examination
    • Abstinence
  • No constipation
  • Drugs:
    • Steroids (< 34 weeks): Enhance fetal lung maturity
    • Tocolysis: Suppress premature labour
    • Antimicrobials
    • Stool softeners
    • Anti-Rh immunoglobulin

Definitive management:

  • Minor degree placenta praevia: Vaginal delivery
  • Major degree placenta praevia: Cesarean section

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