Placenta Previa Classifications And Evaluation
Placenta Previa: Is the development of the placenta in the lower uterine segment, partially or completely covering the internal cervical os.
Traditionally categorized into 3 types:
1- Complete, total or central Previa: internal os entirely covered.
2- Partial : internal os partially covered.
3- Marginal : placenta reaches the edge of the internal os.
– 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.
– 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 labor begins, or complete dilatation has occurred.
– Bleeding occurs earlier and is more profuse with total placenta previa.
– 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).