Makindo Medical Notes

Related Subjects: |Antepartum haemorrhage |Postpartum haemorrhage |Acute Haemorrhage |Placenta praevia |Placenta abruption |Anti-D immunoglobulin

Causes painless vaginal bleeding in pregnancy. Avoid vaginal examination in suspected placenta praevia as it can worsen bleeding.

About

• Placenta praevia is a condition where the placenta is abnormally positioned in the lower segment of the uterus, potentially covering the cervical opening (internal os).
• It is a common cause of painless vaginal bleeding in the second and third trimesters and often necessitates delivery via caesarean section.

Aetiology

• Placenta praevia is observed in approximately 1 in 200 pregnancies.
• There can be rapid and severe blood loss due to the high uterine blood flow, which is around 600-800 mL/min at term.
• Ultrasound (USS) in early pregnancy may show a low-lying placenta, which typically moves up as the uterus grows. However, in some cases, the placenta remains in the lower segment, causing placenta praevia.

Risk Factors and Associations

• Multiple pregnancy (e.g., twins or triplets), which increases placental size.
• Uterine abnormalities, such as fibroids or previous uterine surgery.
• Previous caesarean section or uterine surgery, increasing the risk of abnormal placental attachment.

Clinical Presentation

• Painless vaginal bleeding (antepartum haemorrhage), typically presenting at 29-30 weeks or later.
• Vaginal bleeding may occur without uterine pain, differentiating it from placental abruption.
• Speculum and digital vaginal examinations should be avoided as they can trigger significant bleeding.
• Fetal heart rate is usually normal.
• The uterus remains non-tender, and fetal position is typically normal.

Grades of Placenta Praevia

• Complete: The internal cervical os is entirely covered by the placenta.
• Partial: The internal os is partially covered by the placenta.
• Marginal: The placenta reaches the edge of the cervix but does not cover it.
• Low-lying: The placenta is positioned in the lower uterine segment but does not reach the cervix.

Differential Diagnosis

• Placental abruption: In contrast to placenta praevia, abruption typically causes painful vaginal bleeding and uterine tenderness.

Investigations

• Transabdominal or Transvaginal Ultrasound: The gold standard for diagnosing placenta praevia. Transvaginal USS offers more precise imaging of placental location.
• Blood tests:
  • Full blood count (FBC) to assess for anaemia.
  • Group and crossmatch in case of the need for blood transfusion.
  • Coagulation profile (clotting) to monitor for potential bleeding complications.
  • Baseline U&E (urea and electrolytes) to assess overall health status.
• Cardiotocography (CTG): Fetal monitoring to assess the fetus’s heart rate and wellbeing.

Management

• IV access: Establish good intravenous access in case of the need for fluid resuscitation or blood transfusion.
• Blood transfusion: Transfuse as needed to maintain hemoglobin (Hb) levels >10 g/dL.
• Hospital observation: Some experts recommend hospital admission for observation starting at 35 weeks in high-risk cases, though this is controversial if there has been no bleeding.
• Steroids: Administer corticosteroids to accelerate fetal lung maturity in case of preterm delivery.
• Caesarean section: Delivery via caesarean section is indicated, often scheduled at 37-38 weeks or earlier if bleeding is significant or maternal/fetal distress is present. A consultant-led team is recommended.

Complications

• Hemorrhagic shock: Severe maternal blood loss requiring urgent intervention.
• Preterm birth: Increased risk due to early delivery or emergency interventions.
• Placenta accreta spectrum: Abnormal placental attachment into the uterine wall, increasing the risk of severe hemorrhage during delivery.