••• Chapter 19^ The Placenta and Umbilical Cord^199
❍ What conditions are associated with small placentas?
Maternal hypertension, preeclampsia, polyhydramnios, and fetal IUGR.
❍ What are the small white lesions that can be scraped away from the fetal placental surface?
Desquamated skin cells: Amnion nodosum.
❍ What condition is amnion nodosum associated with?
Long-standing oligohydramnios.
❍ What is the pathognomonic pathological finding of placental microabscesses?
Listeriosis.
PLACENTAL COMPLICATIONS
❍ What is a vasa previa?
Membranous cords in advance of the fetal presenting part, and often across the cervical os. Can occur with
velamentous or marginal insertions, succenturiate lobes, and bilobed placentas.
❍ What is the incidence of vasa previa?
Approximately 1 per 3000 deliveries.
❍ What is the perinatal mortality rate associated with vasa previa?
60% if undiagnosed prenatally.
❍ Why is the perinatal mortality rate of vasa previa so high?
Rupture of the membranes leads to rapid fetal exsanguination.
❍ How is the diagnosis of vasa previa made prior to delivery?
By color flow Doppler techniques define placenta previa: Placenta covering the internal os of the cervix.
❍ What is the incidence of placenta previa at the time of delivery?
0.5% (1 in 200).
❍ Name the factors that increase the risk of placenta previa.
Advancing maternal age.
Multiparity.
Multiple gestation.
African or Asian ethnic background.
Smoking.
Cocaine use.
Prior previa.
Prior cesarean delivery.
Prior suction curettage or uterine surgery.