EMBRYONIC DEVELOPMENT OF THE UMBILICAL CORD
At 3 weeks’ gestation, the developing embryo is connected to the chorion by a connective stalk, which contains the developing umbilical vessels and allantois. The primitive gut develops from the yolk sac and is connected, along with vitelline vessels, to the extracoelomic part via the vitelline duct.
As the embryo grows, the amniotic cavity expands, drawing the connective stalk and vitelline duct together with proteoglycan-rich Wharton jelly to form the primitive umbilical cord.
By the 9th week of gestation, the vitelline duct involutes, whereas the allantois obliterates by the 5th month into the urachus, a fibrous structure that connects the urinary bladder to the umbilicus, to leave behind the umbilical cord composed of 2 umbilical arteries and a single umbilical vein supported by Wharton jelly.
Failure of obliteration of allantois and/or the omphalomesenteric duct (OMD) or vessels either completely or partially can lead to congenital disorders of the umbilical cord.After birth, the umbilical cord should be carefully examined for the presence of 3 vessels, vascular abnormalities (including varicosities), hemangioma, and evidence of cord rupture.
The incidence of a 2-vessel cord with a single umbilical artery is 0.4% to 0.6% of live births.
Although most infants with a single umbilical artery have no coexisting anomalies, approximately 20% to 30% may be associated with congenital abnormalities involving the central nervous, genitourinary, gastrointestinal, or cardiovascular systems.
The incidence of renal anomalies associated with a single umbilical artery is 4% to 16%, most of which are minor anomalies and clinically insignificant. Current evidence does not support routine imaging for detecting anomalies in infants with a single umbilical artery; however, these infants should be carefully examined for dysmorphic features and associated anomalies.
As the embryo grows, the amniotic cavity expands, drawing the connective stalk and vitelline duct together with proteoglycan-rich Wharton jelly to form the primitive umbilical cord.
By the 9th week of gestation, the vitelline duct involutes, whereas the allantois obliterates by the 5th month into the urachus, a fibrous structure that connects the urinary bladder to the umbilicus, to leave behind the umbilical cord composed of 2 umbilical arteries and a single umbilical vein supported by Wharton jelly.
Failure of obliteration of allantois and/or the omphalomesenteric duct (OMD) or vessels either completely or partially can lead to congenital disorders of the umbilical cord.After birth, the umbilical cord should be carefully examined for the presence of 3 vessels, vascular abnormalities (including varicosities), hemangioma, and evidence of cord rupture.
The incidence of a 2-vessel cord with a single umbilical artery is 0.4% to 0.6% of live births.
Although most infants with a single umbilical artery have no coexisting anomalies, approximately 20% to 30% may be associated with congenital abnormalities involving the central nervous, genitourinary, gastrointestinal, or cardiovascular systems.
The incidence of renal anomalies associated with a single umbilical artery is 4% to 16%, most of which are minor anomalies and clinically insignificant. Current evidence does not support routine imaging for detecting anomalies in infants with a single umbilical artery; however, these infants should be carefully examined for dysmorphic features and associated anomalies.
Dr Ibrahim Samaha
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