Placenta Previa

Overview of Placenta Previa

• Placenta previa occurs when the placenta attaches to the lower uterine segment, near or over the internal os (opening between the uterus and cervix).
• Two types of placenta previa:
  • Previa: Placenta covers the internal os, blocking vaginal birth and increasing complications.
  • Low-lying: Placenta near, but not covering the os; may allow for vaginal birth if sufficiently distant (more than 3 cm).

Diagnosis and Signs

• Painless bleeding or abdominal pain/contractions can occur at any pregnancy stage due to placental positioning.
• Hemodynamic instability may arise, leading to blood pressure and heart rate changes from significant blood loss.
• Abnormal fetal heart rate patterns can indicate fetal distress due to disrupted placental blood flow.
• Ultrasound and vaginal exams are essential for confirming placental placement.

Lab Evaluation

• Ultrasound is the key diagnostic tool for determining placental location.
• Early pregnancy ultrasounds (at 11-12 weeks) cannot reliably locate the placenta due to potential migration.
• Anatomy ultrasound at 15-22 weeks provides accurate placental positioning, crucial for managing placenta previa.

Management During Pregnancy

• Regular monitoring of maternal and fetal well-being is essential for detecting complications.
• Cesarean birth is anticipated if the placenta covers the os to minimize risks; vaginal birth may be possible with a low-lying placenta.
• The placenta may shift during cervical dilation, potentially making vaginal delivery unsafe.

Timing and Delivery Considerations

• Vaginal birth is unsafe in cases of placenta previa; a cesarean section is recommended to avoid complications like hemorrhage.
• It is advisable to schedule cesarean delivery close to term but before labor initiation to prevent complications from labor.

Risks Associated with Placenta Previa

• Fetal impacts include impaired blood flow, oxygen delivery issues (hypoxia/anoxia), and increased risk of fetal anemia and growth restrictions.
• Prematurity is common, leading to complications from underdeveloped organs in the newborn.

Maternal Risks

• Severe bleeding may cause hemorrhagic or hypovolemic shock, threatening maternal life.
• Rh sensitization is a risk if the mother is Rh-negative and the fetus is Rh-positive.
• Risk of septicemia due to infection and thrombophlebitis from decreased mobility and increased clotting risk.

Risk Factors for Placenta Previa

• Endometrial scarring from previous placenta previa or cesarean births increases risk.
• Advanced maternal age (over 35), diabetes, and hypertension can impede optimal placental implantation.
• Cigarette smoking reduces uterine blood flow, increasing abnormal placental attachment risk.
• Structural anomalies or fibroids can disrupt normal placental positioning.
• Increased placental mass from large placentas or multiple gestations raises the likelihood of abnormal placement near the os.

This quiz explores the critical aspects of placenta previa, including its types, symptoms, and diagnostic methods. Learn about the implications for pregnancy and delivery in cases where the placenta is improperly positioned. Get familiar with the signs, potential complications, and the evaluation process.