Summary of "Placenta previa - causes, symptoms, diagnosis, treatment, pathology"

Summary of “Placenta previa - causes, symptoms, diagnosis, treatment, pathology”

Definition

Placenta previa occurs when the placenta implants in the lower part of the uterus, near or covering the internal cervical os (uterine opening). This abnormal placement can cause bleeding, typically after 20 weeks of gestation.

Normal vs. Abnormal Placental Implantation

Normally, the placenta implants in the upper uterus. The exact reason for lower implantation in placenta previa is unclear but may be linked to poor vascularization of the upper uterine lining (endometrium).

Risk Factors

Previous uterine damage (e.g., cesarean section, abortion, uterine surgery)
Multiparity (multiple pregnancies)
Multiple placentas or larger placental surface area (e.g., twins, triplets)
Maternal age ≥ 35 years
Intrauterine fibroids
Maternal smoking

Classification of Placenta Previa

Based on the placenta’s proximity to the cervical os:

Complete: Placenta completely covers the cervical os
Partial: Placenta partially covers the cervical os
Marginal: Placenta edge is within 2 cm of the cervical os

Pathophysiology and Symptoms

As pregnancy progresses, the lower uterine segment grows, which can disrupt placental blood vessels if the placenta is low-lying, causing bleeding.

Bleeding is usually sudden, painless, and bright red, occurring after 20 weeks gestation
Bleeding can be intermittent or continuous and may increase during labor due to contractions and cervical dilation

Complications

Maternal: Severity of blood loss
Fetal: Hypoxia, preterm delivery
Associated condition: Placenta accreta (placenta invades the uterine muscle, making separation difficult)

Diagnosis

Placenta previa is mostly diagnosed via prenatal ultrasound. Sometimes it is first noticed during labor when bleeding occurs.

Treatment and Management

The main goals are to prevent preterm birth and manage maternal bleeding:

Corticosteroids may be administered to promote fetal lung maturity
Minor bleeding: Bed rest
Major bleeding: Blood transfusions and IV fluids to maintain hemodynamic stability
Severe cases with maternal instability and fetal distress: Immediate cesarean section

Recap

Placenta previa involves a placenta implanted low in the uterus, potentially covering the cervical opening. It causes painless, bright red bleeding after 20 weeks and increases the risks of preterm birth and fetal hypoxia.

Speakers/Sources Featured

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