Placenta Previa

Background

Placenta previa
- Definition : presence of placental tissue that extends over the internal cervical os
- Estimated to affect 1/200 pregnancies.
- Known placenta previa necessitates cesarean birth somewhere between 36 to 37+6 gestational age
Placenta accreta spectrum includes 3 sub-types. The most important risk factor for developing these is placenta previa after a prior cesarean delivery
- Accreta: placenta adhered to myometrium without invasion through uterine muscle
- Increta: invasion of myometrium
- Percreta: invasion of uterine serosa and other structure

Considerations

Pregnancy considerations (difficult intubation, aspiration, quick desaturation, aortocaval compression, 2 patients)
Increased risk of antepartum hemorrhage and the need for resuscitation and possibly emergency delivery
Increased risk of intra-operative blood loss even without pre-operative bleeding due to injury by obstetrician to an anteriorly located placenta during uterine incision and low uterine tone of the lower uterine segment implantation site

References

Chestnut's Obstetric Anesthesia, 6th Edition. Chapter 37: Anterpartum and Postpartum Hemorrhage.