Placenta Previa

Placenta Previa

Placenta Previa

Is the development of the placenta in the lower uterine segment, partially or completely covering the internal cervical os.

Classifications:

Traditionally categorized into 3 types:

1- Complete, total or central Previa: internal os entirely covered.

2- Partial placenta previa: internal os partially covered.

3- Marginal placenta previa: placenta reaches the edge of the internal os.

Aetiology:

- Specific causes are unknown.

Implantation may be affected by:

1. Abnormality of endometrial vascularity.

2. Delayed ovulation.

3. Prior endometrial trauma.

4. Multiple pregnancies.

5. Previous uterine surgery.

Clinical manifestations:

- Usually presents as painless vaginal bleeding in the 3rd trimester but can occur as early as 20 weeks of gestation bleeding occurs without warning in the absence of trauma.

- Blood loss from the first bleeding is rarely fatal, in each subsequent episode bleeding is heavier.

- Placenta previa may not cause bleeding until labour begins, or complete dilatation has occurred.

- Bleeding occurs earlier and is more profuse with total placenta previa.

Diagnostic evaluation:

- Painless vaginal bleeding is placenta previa until proven otherwise.

- Ultrasound is the diagnostic technique of choice.

- Definitive diagnostic by direct palpation of the placenta is not recommended.

Vaginal examination " double setup procedure ":

- Under sterile technique by the physician after diagnosis by ultrasound.

- Inconclusive ultrasound or only low –lying placenta noted.

Note: the term low-lying implantation is used when the placenta situated in the lower uterine segment but away from the os.

- Sterile speculum examination performed first.

- It is attempted only if the physician and the women are prepared for cesarean delivery in the operating room.

- If greater than 3cm dilated and no placenta covering os, then perform amniotomy ( by the physician).


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