198 Obstetrics and Gynecology Board Review •••
❍ Where is the preferred site for ultrasound-guided cordocentesis?
The umbilical vein at its placental origin.
EVALUATION
❍ What time period denotes the third stage of labor?
From delivery of the infant to delivery of the placenta.
❍ Name three signs of placental separation during the third stage of labor.
Increased vaginal bleeding, lengthening of the umbilical cord, and changing of the shape of the abdominally
palpated uterus to a more globular shape.
❍ What duration of time of the third stage of labor defines a retained placenta?
30 minutes.
❍ What are the complications of retained placenta?
Infection and postpartum hemorrhage.
❍ What location of the placenta is associated with uterine inversion?
Fundal.
❍ What characteristics of the placenta should be noted once the placenta is delivered?
Time of delivery, cord insertion, number of vessels in cord, clinical evidence of infection or meconium staining,
and completeness of the maternal surface and membranes.
❍ What information about the placenta should be noted on a routine second or third trimester ultrasound?
Placental location, relationship to the internal cervical os, grade, and any evidence of abruption.
❍ Increasing placental maturity is associated with what ultrasound finding?
Increased echogenicity secondary to increased calcium deposits.
❍ What conditions are associated with abundant placental calcifications prior to 36 weeks?
Intrauterine growth restrictions (IUGR), oligohydramnios, maternal hypertension, diabetes, and smoking.
❍ What is the average weight of the term placenta?
450 g.
❍ What defines placentomegaly?
Weight >600 g, or ultrasound thickness >4 cm.
❍ What conditions are associated with placentomegaly?
Maternal diabetes, maternal or fetal anemia, chronic infection, hydrops fetalis, and Beckwith-Wiedemann syndrome.