🩸 Placenta Praevia

Course Overview

Placenta praevia is a potentially serious obstetric condition characterized by the implantation of the placenta in the lower uterine segment, either partially or completely covering the internal cervical os. It is an important cause of painless antepartum haemorrhage and is a leading contributor to maternal and perinatal morbidity and mortality. Early diagnosis and careful management are crucial for optimal outcomes.

This expert module explores the pathophysiology, clinical presentation, investigations, and evidence-based management of placenta praevia, focusing on safe delivery planning and prevention of maternal-fetal complications.

Learning Objectives

By the end of this module, learners should be able to:

1. Define and classify placenta praevia.

2. Identify predisposing and risk factors for placenta praevia.

3. Recognize its characteristic clinical presentation.

4. Outline appropriate diagnostic investigations.

5. Formulate management plans based on maternal stability and gestational age.

6. Describe delivery and postpartum care strategies for patients with placenta praevia.

 Introduction and Description

Placenta praevia refers to the abnormal implantation of the placenta in the lower uterine segment. Depending on its relationship to the internal cervical os, it can be classified as low-lying, marginal, partial, or complete placenta praevia.
This abnormally situated placenta predisposes to painless, bright red vaginal bleeding in the second half of pregnancy, typically after 20 weeks of gestation. The bleeding results from separation of the placenta as the lower uterine segment stretches and thins in late pregnancy.

 Risk Factors and Predisposing Conditions

Several maternal and obstetric factors increase the risk of placenta praevia. These include previous uterine operations such as caesarean section or myomectomy, multiple pregnancies, fetal macrosomia, and advanced maternal age.
Other associated factors may include multiparity, smoking, assisted reproductive techniques, and previous placenta praevia. The risk increases with the number of prior caesarean sections, due to scarring and altered endometrial receptivity in the lower segment.

 Clinical Presentation

The hallmark of placenta praevia is painless vaginal bleeding, typically bright red in color and occurring without associated uterine contractions. The bleeding may vary in amount, often occurring spontaneously and recurrently, and may be accompanied by symptoms of anaemia such as headache, dizziness, or palpitations.

On examination, the patient is usually not in pain. The uterus is soft, relaxed, and non-tender, and corresponds to the gestational age. Fetal parts are easily palpable, and the fetal heart rate is usually normal. Malpresentations such as breech or transverse lie are common due to the low-lying placenta preventing normal engagement of the fetal head.
Signs of anaemia or shock may be present in severe bleeding episodes. Importantly, digital vaginal examination is contraindicated as it may provoke torrential haemorrhage.

 Diagnostic Investigations

Diagnosis of placenta praevia relies on both clinical suspicion and imaging studies.
The first step is a complete blood count (FBC) to assess haemoglobin and haematocrit levels, along with blood grouping and cross-matching in anticipation of possible transfusion.
Obstetric ultrasound is the definitive investigation and should be performed transabdominally or transvaginally (the latter only in a controlled hospital setting) to determine the placental location and exclude placenta accreta.

Other essential investigations include assessment of maternal haemodynamic stability, baseline renal and liver function, and fetal wellbeing through ultrasound biometry and doppler assessment.

 Management Principles

Management of placenta praevia depends on the severity of bleeding, maternal haemodynamic stability, and gestational age.

A. Expectant Management (Conservative Care)

If the bleeding is minimal, the patient is haemodynamically stable, and the gestational age is less than 38 weeks, expectant management is appropriate.
The patient should be admitted to the antenatal ward for observation and monitoring. A clearly visible delivery plan should be written on the first page of the patient’s chart in capital letters and red ink.
A large-bore intravenous line (14–18 gauge) should be inserted and maintained at all times for immediate fluid resuscitation if needed.

Full blood count should be checked twice weekly, maintaining a haemoglobin level above 10 g/dL.
Bleeding should be monitored through pad count and inspection, while vital signs (pulse, blood pressure, respiratory rate, and oxygen saturation) are recorded every four hours.
Twice-weekly ultrasound assessments are performed to monitor fetal growth, activity, and placental position for possible migration upward with advancing gestation.

Fetal heart rate monitoring should be performed using a Pinard stethoscope or Doppler, and a kick chart should be maintained by the mother.
A minimum of two units of cross-matched blood should always be available in the ward or blood bank.
Corticosteroids should be administered for fetal lung maturity if preterm delivery is anticipated — for example, dexamethasone 6 mg intramuscularly every 12 hours for four doses or betamethasone 12 mg intramuscularly once daily for two days.
Continue all other antenatal investigations and medications according to the antenatal care schedule.
Avoid unnecessary abdominal palpation and encourage bed rest in the left lateral position to optimize uteroplacental perfusion.
Digital vaginal examination is absolutely contraindicated.

If at any point the bleeding becomes heavy, or preterm labour is established, the obstetric team on call must be notified immediately for emergency caesarean section.

B. Delivery Plan

The aim is to deliver at 38 completed weeks by caesarean section, performed by an experienced obstetrician.
The delivery should take place in a facility with adequate blood transfusion services and neonatal resuscitation capability.
The team must anticipate postpartum haemorrhage (PPH) due to uterine atony or placental site bleeding and prepare uterotonics, intravenous fluids, and blood products in advance.

If the bleeding is profuse, or the patient is already at term, or in cases where the fetus is dead or has major congenital anomalies, immediate delivery by caesarean section is indicated regardless of gestational age.

 Complications and Postpartum Care

Placenta praevia may lead to several complications including massive antepartum haemorrhage, maternal anaemia, hypovolemic shock, disseminated intravascular coagulation (DIC), preterm labour, intrauterine growth restriction, and perinatal death.
During caesarean delivery, there is an increased risk of placenta accreta spectrum disorders, uterine rupture, and postpartum haemorrhage.

Postpartum care includes monitoring vital signs, uterine tone, and vaginal bleeding, ensuring adequate pain control, maintaining haemoglobin levels, and providing psychosocial support. The newborn should be assessed for prematurity and anaemia, and admitted to neonatal care if required.

 Key Summary Points

Placenta praevia is an abnormally low-lying placenta that may partially or completely cover the cervical os. It presents as painless, bright red vaginal bleeding in the second half of pregnancy.
Diagnosis is confirmed by obstetric ultrasound, and management depends on maternal condition and gestational age.
Digital vaginal examination is contraindicated.
Expectant management may be pursued if the mother is stable and the fetus is preterm, but delivery by caesarean section at 38 weeks is the goal in most cases.
Active preparedness for postpartum haemorrhage and coordinated multidisciplinary care are essential for maternal and neonatal safety.

Recommended References

• World Health Organization. WHO Recommendations for the Prevention and Treatment of Postpartum Haemorrhage.

• Cunningham FG et al. Williams Obstetrics, 27th Edition.

• NICE Guidelines NG201 (2021): Intrapartum Care: Care of Healthy Women and Their Babies During Childbirth.

• Ministry of Health Zambia. Obstetric and Perinatal Care Protocols.