Placenta Previa Flashcards
Definition of placenta previa
abnormal implantation of placenta over the internal cervical os
Complete previa
placenta completely covers internal cervical os
Partial previa
placenta covers portion of internal cervical os
Marginal previa
edge of placenta reaches margin of the internal cervical os
Low-lying placenta
placenta that is implanted in the lower uterine segment close proximity but not reaching margin of the os
Vasa previa
fetal vessel covering cervix d/t atrophy of a placental segment overlying the less well vascularized cervix when a velamentous cord insertion passes over cervical os
What is the probable reason that 90% of low-lying placentas appear to move away from the cervix and out of the lower uterine segment?
d/t development of lower uterine segment and trophotropism (growth preferentially toward a better vascularized fundus)
Succenturiate lobe
an incomplete atrophy of a segment of the placenta that leaves a placental lobe discrete from the rest of the placenta
What is the estimate of maternal mortality in cases of placenta previa?
What is the cause (and %) of most perinatal deaths in this situation?
0.03%
Premature delivery is responsible for 60% of perinatal deaths
What are fetal complications associated with placenta previa?
preterm delivery (and its complications) PPROM (and its complications) IUGR Malpresentation Vasa previa Congenital abnormalities
Placenta acreta
Average blood loss?
Sequelae?
superficial attachment of the placenta to uterine myometrium (increased incidence in placenta previa)
3-5 L average blood loss
hemorrhage and shock –> hysterectomy, surgical injury to ureters/bladder/viscera, ARDS, renal failure, coagulopathy, death, spontaneous uterine rupture (2T, 3T) –> intraperitoneal hemorrhage
Placenta increta
placental invasion of the myometrium (but not through)
Placenta percreta
placenta invasion through myometrium into the uterine serosa
What is historically the most frequent indication for peripartum hysterectomy?
What about now?
Historically, Uterine atony
Now, abnormal placentation/placenta accreta
Velamentous placenta
occurs when blood vessels insert between amnion and chorion away from margin of placenta, leaving vessels vulnerable to compression/injury
How often does placenta previa occur?
1:200 births
In what % of women does placenta previa occur in women with prior C-sections?
1-4% of women with prior C-sections
How often does placenta accreta complicate placenta previa?
5% of cases
Placenta increases by ___ % in the setting of:
1 prior C-section
2 prior C-sections
3+ prior C-sections
1) 15-30%
2) 25-50%
3+) 29-67%
Predisposing factors for placenta previa
Prior C-section/Uterine surgery/Prior uterine scars Multiparity Multiple gestation Erythroblastosis Smoking Hx placenta previa Increased maternal age
Classical S&S
sudden, profuse PAINLESS vaginal bleeding
Sentinel bleed
What is it?
When does it occur?
first episode of bleeding
generally after 28 wks GA
On physical exam, is vaginal examination warranted?
No. Vaginal exam is contraindicated in previa because digital examination can cause further separation and trigger hemorrhage.
What is the sensitivity of US for diagnosis of placenta previa?
What method is preferred?
95%
transvaginal US
