Placenta praevia is an obstetric complication in which the placenta implants partially or wholly over the cervix. This condition can lead to significant maternal and fetal risks, primarily due to bleeding.
Classification:
Placenta praevia is classified based on the degree of cervical coverage:
Grade I (Low-Lying): The placenta is low-lying but does not cover the cervix.
Grade II (Marginal): The placenta reaches the cervix but does not cover it.
Grade III (Partial): The placenta partially covers the cervical os.
Grade IV (Complete): The placenta completely covers the cervical os.
Epidemiology:
Occurs in approximately 0.5% of all pregnancies.
The incidence is higher in women with previous cesarean sections, multiple gestations, and those who smoke or use cocaine.
Risk Factors:
Previous placenta praevia
Multiple gestations
Advanced maternal age
Smoking and substance abuse
Previous uterine surgery, including cesarean section
High parity
Clinical Features
Signs and Symptoms:
Painless, bright red vaginal bleeding in the second or third trimester is the hallmark symptom.
Bleeding may be associated with uterine contractions in some cases.
The fetus may present in a non-cephalic position due to abnormal placental location.
Diagnosis:
Ultrasound: The primary diagnostic tool, preferably transvaginal ultrasound, which offers a detailed view of the placental location relative to the cervix.
Physical examination should be cautious to avoid triggering bleeding.
Management
Antepartum Care:
Expectant management for asymptomatic cases or mild bleeding, with close monitoring and hospitalisation if necessary.
Activity restriction, including pelvic rest (no intercourse, no vaginal exams unless absolutely necessary).
Planning for delivery at a tertiary care centre with facilities for maternal and neonatal care.
Delivery Planning:
Cesarean delivery is indicated for all cases of complete placenta praevia and most cases of partial praevia.
The timing of delivery depends on the gestational age, fetal maturity, and severity of bleeding: aiming for delivery at 36-37 weeks if possible, or earlier if maternal/fetal status warrants.
Intrapartum Care:
Immediate management of bleeding may include tocolytics to delay labour (if preterm), corticosteroids for fetal lung maturity (if preterm), and blood transfusions if significant blood loss occurs.
Multidisciplinary approach involving obstetricians, anesthesiologists, and neonatologists.
Complications
Maternal: Significant risk of hemorrhage, which can lead to shock and require transfusion. Increased risk of hysterectomy.
Fetal: Prematurity, low birth weight, and fetal distress due to bleeding.
With appropriate management, the outcome for most cases of placenta praevia is positive.
The key to managing placenta praevia is early detection, careful monitoring, and planning for delivery in a controlled setting.
Summary
Placenta Praevia is a critical condition in obstetrics characterized by the placenta covering the cervix, leading to potential severe bleeding in the second half of pregnancy. Medical students should understand its classification, risk factors, clinical presentation, and management principles. The focus on antepartum care, delivery planning, and addressing complications is crucial for ensuring the safety of both mother and baby.
