[Placenta previa--from the past to the present]

Area of Science:

• Obstetrics and Gynecology
• Diagnostic Imaging
• Maternal-Fetal Medicine

Background:

• Traditional methods like X-ray and radioisotope placentography for diagnosing placenta praevia are compared with modern ultrasound techniques.
• Placenta praevia diagnosis has evolved, impacting patient management and outcomes.
• Understanding the incidence and progression of placenta praevia is crucial for prenatal care.

Observation:

• Prenatal diagnosis of placenta praevia is achieved through transabdominal and transvaginal ultrasound.
• The frequency of placenta praevia decreases as pregnancy progresses, a phenomenon attributed to placental migration.
• Placental edge proximity to the cervical os at 20 weeks gestation predicts the likelihood of requiring Cesarean delivery.

Findings:

• Ultrasound allows for earlier and more accurate diagnosis of placenta praevia, minimizing prolonged hospitalization and elective Cesarean sections.
• Placental migration is a key factor; if the placental edge is >2 cm from the cervical os, migration occurs, avoiding Cesarean delivery.
• Conversely, if the placenta overlaps the cervical os by >20 mm at 26 weeks, Cesarean delivery is typically required.

Implications:

• Routine 20-week obstetric sonograms are recommended for all pregnant women to screen for placenta praevia.
• Transvaginal ultrasound should be employed when the placental location relative to the internal os is unclear on transabdominal scans.
• Targeted follow-up ultrasounds (around 34-35 weeks) for cases with a low placental edge (<1 cm from internal os) can optimize delivery planning and reduce maternal and fetal morbidity.