Placenta Previa
Background
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Placenta previa
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Definition : presence of placental tissue that extends over the internal cervical os
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Estimated to affect 1/200 pregnancies.
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Known placenta previa necessitates cesarean birth somewhere between 36 to 37+6 gestational age
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Placenta accreta spectrum includes 3 sub-types. The most important risk factor for developing these is placenta previa after a prior cesarean delivery
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Accreta: placenta adhered to myometrium without invasion through uterine muscle
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Increta: invasion of myometrium
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Percreta: invasion of uterine serosa and other structure
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Considerations
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Pregnancy considerations (difficult intubation, aspiration, quick desaturation, aortocaval compression, 2 patients)
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Increased risk of antepartum hemorrhage and the need for resuscitation and possibly emergency delivery
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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
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Chestnut's Obstetric Anesthesia, 6th Edition. Chapter 37: Anterpartum and Postpartum Hemorrhage.