Congenital malformations - Edocr

Chapter 48
Single Umbilical Artery
PRAVEEN KUMAR
INTRODUCTION
The umbilical cord is an important part of the
fetoplacental unit and is vital to the growth and
well-being of the fetus. A normal umbilical cord
is about 50–60 cm long at term and contains
two arteries and one vein which course through
Wharton’s jelly in a helical fashion. Single umbilical
artery, a condition in which only one
umbilical artery is present, is one of the most
common congenital malformations in a human
infant. Although presence of a single umbilical
artery was noted as early as the mid-sixteenth century,
its association with various other congenital
malformations was reported by Benirschke and
Brown in 1955. Since then several reports from
different parts of the world have confirmed a
higher incidence of associated malformations in
infants with single umbilical artery.
EPIDEMIOLOGY
The incidence of single umbilical artery has been
reported to be 1.5–7% among abortuses, 0.2–1.6%
among euploid fetuses, 9–11% among aneuploid
fetuses, and 0.5–2.5% among uncomplicated
neonates. 1–3 The overall incidence of single umbilical
artery in unselected populations has been
reported to range from 0.3% to 1.07%. 4–6 These
differences in incidence rates are related to
method of diagnosis such as, prenatal ultrasound
diagnosis or postnatal examination of the cord
versus histopathological examination of the placenta
or cord. The histopathological examination
of the cord is considered to be the gold standard
but it is important to note that the two arteries
may fuse close to the placental insertion of the
cord and examination at this point would overestimate
the incidence. 1 The sensitivity of prenatal
ultrasound for diagnosis of single umbilical
artery has been reported to range from 30% to
85% depending on the experience of the sonographer
as well as the indication for ultrasound,
routine versus anatomic survey for congenital
malformations. 2,5,7 A study evaluating physician’s
ability to diagnose single umbilical artery on postnatal
examination reported that the diagnosis of
single umbilical artery was missed by 24% of
obstetricians and 16% of pediatricians on examination
of cord. 7
Single umbilical artery is reported to be less
common in patients with Japanese and African
ancestry and is more common in those from
Eastern Europe. 1,8 A significantly higher incidence
has been noted in pregnancies associated
with multiple gestations, maternal diabetes, and
hypertension. A higher incidence of abnormalities
of placenta such as marginal insertion and velamentous
insertion of cord has also been noted. 9
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