Placenta Previa: Definition, Diagnosis, Management, and Precautions

1. Definition:

Placenta previa (PP) is a condition in which the placenta attaches to the lower segment of the uterus, covering all or part of the cervix.

2. Reasons for diagnosing PP only in the last trimester:

• Cervical structure: The normal cervical os is only about 0.5-1cm in diameter. During the late pregnancy, the lower uterine segment stretches, the cervical os widens, creating a favorable environment for ultrasound to detect placenta attachment in this location.
• Fetal development: The fetus grows larger, and the placenta follows suit, increasing in size and putting pressure on the cervix, which is easily recognizable through ultrasound.

3. Mechanism of bleeding in PP:

• Stretching of the lower uterine segment: When the uterine segment is stretched due to fetal size, the placenta, which lacks the ability to stretch, can detach from the uterine wall, causing bleeding.
• Bright red blood mixed with clots: The blood flows from the uterine artery, typically bright red, sometimes mixed with clots.

4. Clinical features of PP:

• Vaginal bleeding: Recurring bleeding, in episodes, self-stopping, usually without abdominal pain.
• No labor: PP usually does not cause abdominal pain, and is not accompanied by labor.
• Fetal heart rate is almost normal: Fetal heart rate changes only when central PP causes excessive bleeding and shock.

5. Diagnosing PP:

Ultrasound: This is the most accurate diagnostic method, which helps to determine the placenta location and the degree of cervical coverage.

6. Differentiating PP from Placental abruption (PA):

Feature	Placenta Previa	Placental Abruption
Blood color	Bright red, with clots	Dark red
Blood loss	Measurable blood loss	Unmeasurable blood loss
Patient’s condition	Usually no shock	Quick shock if not intervened promptly
Fetal heart rate	Only changes with excessive bleeding	Changes significantly with placental abruption
Management	Medical management	Emergency treatment

7. Reasons for different management of PP and PA:

• PA: Fetal heart rate changes significantly, and there is a hematoma, necessitating urgent intervention to save the fetus and mother.
• PP: Fetal heart rate only changes when bleeding is excessive, there is no hematoma, so medical treatment is possible.

8. Indications for termination of pregnancy with PP:

• Excessive bleeding: Uncontrolled bleeding, endangering the mother’s life.
• Severe fetal distress: Abnormal fetal heart rate, fetal growth restriction.

9. Management of PP:

• Tocolysis: Using medications to reduce uterine contractions, minimizing the risk of bleeding.
• Lung maturation: Using corticosteroids to help the fetus mature its lungs, reducing the risk of respiratory complications after birth.
• Birth plan: Choosing a suitable birth method, planning for emergency intervention.

10. Termination of pregnancy with a previous cesarean section:

• Week 38: This is the ideal time, reducing the risk of complications.
• After 39 weeks: If there are abnormalities, termination of pregnancy can be performed.

11. Amniotomy:

• Nature: Amniotomy is not a trigger for labor, but a way to induce effective contractions in cases of polyhydramnios.
• Classification:
  • Bulging membranes: Amniotomy outside of contractions.
  • Flat membranes: Amniotomy during contractions.
• Note: After amniotomy, do not rupture the membranes immediately, but wait for the baby’s head to touch the hand before rupturing the membranes.

12. Placenta accreta index on ultrasound:

• >12: Very high risk of PP.
• 8-12: High risk of PP.

Note:

• Early diagnosis of PP: Helps to monitor pregnancy and manage it promptly, reducing the risk of complications.
• Comprehensive counseling: Doctors need to clearly explain to the pregnant woman about the condition, treatment methods, and the risks of complications.
• Close pregnancy monitoring: Health checks, regular ultrasound scans, monitoring blood loss, and fetal heart rate.

Contact information:

• Note: This article is only for informational purposes and does not replace professional advice from a doctor.
• If you have any health concerns: Please contact a specialist for advice and timely treatment.