From the Guidelines
Placental bleeding when placental tissue is present on the cervical os (placenta previa) occurs because the placenta has implanted in an abnormal location over or near the cervical opening, causing disruption of the attachment between the placenta and uterine wall and tearing of delicate blood vessels as the cervix dilates. This condition is a significant risk to both maternal and fetal health, and its management is crucial to prevent uncontrolled vaginal bleeding and potential complications.
Key Factors Contributing to Placental Bleeding
- The lower uterine segment must stretch and thin during the third trimester and early labor, which can disrupt the placental attachment and lead to bleeding 1.
- The cervical area has an abundant blood supply, and when the placenta is implanted in this location, there is no mechanism for the blood vessels to contract and seal off when disrupted, leading to severe bleeding 1.
- The risk of placenta previa and associated bleeding is increased in women with a history of cesarean delivery, with the risk increasing with the number of prior cesarean deliveries 1.
Clinical Implications and Management
- Placenta previa is a significant risk factor for placenta accreta spectrum disorder (PASD), which can lead to severe and life-threatening hemorrhage during delivery 1.
- Accurate antenatal diagnosis and planning for delivery at an experienced center are essential to reduce maternal morbidity and mortality 1.
- Management of delivery may involve planned cesarean delivery with or without hysterectomy, depending on the suspected severity of PASD, and a contingency plan for emergent delivery should be in place 1.
From the Research
Placental Bleeding Causes
- Placental tissue on the cervical os can cause placental bleeding due to the placenta covering or being proximate to the internal cervical os, leading to bleeding when the cervix dilates or when the placenta separates from the uterus 2.
- The presence of placental tissue on the cervical os can lead to bleeding due to the disruption of the placental attachment to the uterus, resulting in maternal and fetal complications 3, 4.
Risk Factors for Placental Bleeding
- Prior cesarean delivery, advanced maternal age, and smoking are key risk factors for placenta previa, which can cause placental bleeding 2.
- The use of tocolytic agents to stop associated contractions in cases of third-trimester bleeding may not increase the risk of maternal morbidity or mortality, but may prolong pregnancy and increase birth weight 4, 5.
Management of Placental Bleeding
- Expectant management of placenta previa, including the use of tocolytics, blood transfusion, and cesarean section, can be effective in managing placental bleeding 3, 4.
- A planned cesarean delivery is recommended in cases of placenta previa that persist into the late third trimester 2.
- The optimal timing of antenatal corticosteroids in women with bleeding placenta previa or low-lying placenta can be optimized by identifying women at low risk of imminent delivery 6.