From the Guidelines
Placenta previa typically presents with painless, bright red vaginal bleeding during the second or third trimester of pregnancy, and immediate medical attention is necessary if bleeding occurs to prevent significant maternal hemorrhage and fetal compromise. The bleeding is often sudden and may range from light spotting to heavy hemorrhage, sometimes occurring after sexual intercourse 1. Some patients may experience no symptoms until labor begins. Other signs include abnormal fetal presentation (such as breech or transverse) due to the placenta occupying the lower uterine segment. Importantly, placenta previa rarely causes pain unless accompanied by contractions or placental abruption.
Key Signs and Symptoms
- Painless, bright red vaginal bleeding
- Sudden onset of bleeding, ranging from light spotting to heavy hemorrhage
- Abnormal fetal presentation (e.g., breech or transverse)
- No symptoms until labor begins in some cases
- Rarely causes pain unless accompanied by contractions or placental abruption Diagnosis is confirmed through ultrasound imaging, with transvaginal US being particularly helpful in evaluating cervical-related causes of second and third trimester vaginal bleeding 1. Management typically involves pelvic rest (no intercourse, vaginal exams, or tampons), monitoring, and often planned cesarean delivery. The bleeding occurs because as the lower uterine segment stretches and thins during pregnancy, it disrupts the attachment between the placenta and uterine wall, exposing maternal blood vessels. Patients with placenta previa should be educated about the importance of reporting any bleeding immediately and having a plan for rapid transportation to a hospital if heavy bleeding occurs.
From the Research
Placenta Previa Signs and Symptoms
- Placenta previa is a potentially life-threatening cause of bleeding, typically identified during routine second-trimester ultrasound 2.
- Key risk factors for placenta previa include prior cesarean delivery, advanced maternal age, and smoking 2.
- Common signs and symptoms of placenta previa include vaginal bleeding, which can be severe and require hospitalization 3, 4.
- Women with asymptomatic placenta previa can continue normal activities, but those with persistent previa in the third trimester may require pelvic rest and hospitalization if significant bleeding occurs 3.
Associated Conditions and Complications
- Placenta previa is often associated with other conditions, such as placenta accreta and vasa previa, which can increase the risk of complications 2, 3.
- Severe bleeding due to placenta previa can lead to hospitalization and delivery, but does not necessarily increase the risk of adverse maternal or neonatal outcomes 4.
- Women with placenta previa may require antenatal corticosteroids to reduce the risk of preterm birth, and the optimal timing of administration is crucial to maximize effectiveness 5.
Predictive Factors and Sonographic Markers
- Certain sonographic features, such as placental distance past the cervical os (DPO) and cervical length (CL), may be associated with an increased risk of vaginal bleeding in placenta previa 6.
- A decreased CL (<4cm) has been shown to be independently associated with an increased risk of vaginal bleeding in placenta previa 6.
- However, the predictive value of sonographic markers for vaginal bleeding in placenta previa is limited, and further research is needed to identify reliable predictors 6.