••• Chapter 19^ The Placenta and Umbilical Cord^197
❍ What is the average length of the umbilical cord?
60 cm.
❍ What length is defined as a short umbilical cord?
<40 cm.
❍ What complications are associated with a short umbilical cord?
Delivery: Avulsion of the cord, abruption, and uterine inversion.
Fetal: Congenital anomalies and CNS problems.
❍ What length is defined as a long umbilical cord?
70 cm.
❍ What complications are associated with a long umbilical cord?
Cord prolapse, cord entanglement of the fetus, and true knots.
❍ What is the incidence of true knot in a cord?
1.0%.
❍ What percentage of true knots are associated with intrauterine fetal demise?
5% to 10%.
❍ What is the perinatal mortality rate with cord prolapse?
5%.
❍ What are the risk factors for cord prolapse?
Excessive cord length, malpresentation, low birth weight, grand multiparity, multiple gestation, obstetric
manipulation (eg, artificial rupture of membranes), and polyhydramnios.
❍ What is the fetal heart tracing abnormality seen with cord prolapse?
Sustained bradycardia or profound variable deceleration.
❍ What is the incidence of nuchal cord?
25% overall, 21% with one nuchal cord, and 4% with two or more nuchal cords.
❍ What is the incidence of single umbilical artery?
1%.
❍ What significance does a single umbilical artery have with congenital anomalies?
15% of fetuses with congenital anomalies have a single umbilical artery. However, most infants born with a single
umbilical artery have no known anomalies.