The Umbilical Cord Flashcards
What is the essential link for oxygen and important nutrients between the fetus the mother?
The umbilical cord
The _________ covers the cord and blends with the fetal skin at the umbilicus
amnion
The vascular connections within the cord serve a _____ function in the fetus
reverse
The umbilical vein carries ______ blood to the fetus.
oxygenated
The umbilical arteries bring ____ blood back to the ____.
used or deoxygenated blood,
placenta
When does the umbilical cord form?
First 5 weeks of gestation
The umbilical cord is made from the fusion of :
the omphalomesenteric (or yolk stalk) and allantoic ducts
Omphalomesenteric AKA
yolk stalk
An out-pouching from the urinary bladder forms the
urachus, which projects into the connecting stalk to form the allantois
The allantoic vessels become the _____ ______ ______.
definitive umbilical vessels
The umbilical cord is covered by the _______.
amniotic membrane.
The cord includes ___ arteries and ___ vein.
2, 1
What surrounds the vasculature in the umbilical cord?
Wharton’s Jelly
Diameter of umbilical cord:
1-2cm
Length of the umbilical cord:
40-60cm long
Describe the pathway of the umbilical arteries
arise from the fetal internal iliac arteries, course alongside the fetal bladder, and exit the umbilicus to form part of the umbilical cord
The paired umbilical arteries course along the entire length of the cord in a helicoidal fashion surrounding the umbilical vein
They then branch along the chorionic plate of the placenta
The umbilical vein enters the umbilicus and joins the
left portal vein
What happens to the intraabdominal portions of the umbilical vessel after birth?
they degenerate
What do the umbilical arteries become after birth?
lateral ligaments of the bladder
What does the umbilical vein become after birth?
round ligament of the liver.
From the left portal vein, the umbilical blood flows either through the ______ to the systemic veins bypassing the liver or through the ________ to the right portal vein.
ductus venosus,
right portal sinus
The _________ forms the conduit between the portal system and the systemic veins
ductus venosus
The ductus venosus is ____ during fetal life
patent, after birth it becomes the ligamentum venosum
The umbilical arteries run along which margin of the fetal bladder?
lateral margin
In the post partum stage, what do the umbilical arteries become?
superior vesical arteries
In the first trimester, the umbilical cord length should be the same as what?
crown-rump length
A long umbilical cord measures greater than
80 cm
What may long umbilical cords be associated with or predisposed to?
Hint: 5 things
Polyhydramnios Nuchal cord (occurs in 25% of deliveries) True cord knots Umbilical cord compression Umbilical cord stricture or torsion
A short umbilical cord measures
less than 35 cm in length
A short umbilical cord is associated with or predisposed to what 7 things?
Oligohydramnios Restricted space Intrinsic fetal anomaly Tethering of the fetus by an amniotic band Inadequate fetal descent Cord compression Fetal distress
T/F: Coiling of the umbilical cord is normal?
True, related to fetal activity
How often may the normal cord coil?
40 times, usually to the left and near fetal insertion site
The helical twisting of the cord can be easily determined by
gross pathologic inspection
The incidence of a “left” twist of the cord is found in
7:1 pregnacies
A fetus with a “right” twist in the cord has a higher incidence of
anomalies than one with a left twist
T/F: umbilical cord masses are common
False, many “masses” may be attributed to focal accumulation of Wharton’s jelly and may be isolated or associated with an omphalocele or cyst
A cystic mass in the cord is usually ______ or _______ in origin
omphalomesenteric or allantoic
Cysts persisting past the first trimester are associated with :
other fetal anomalies and aneuploidy
10 masses associated with the umbilical cord are:
Omphalocele Gastroschisis Umbilical herniation Teratoma Aneurysm Varix of the cord Hematoma True knot Angioma Thrombosis
What is omphalocele?
Failure of the intestines to return to the abdomen
An omphalocele may consist of
a single loop of bowel or most of the intestines and/or liver
Omphaloceles are completely covered by
epithelium from the umbilical cord
What is gastroschisis?
A right paraumbilical defect involving all layers of the abdominal wall
The _____ always eviscerates with gastroschisis.
small bowel, but other organs that can possibly eviscerate are large bowel, stomach, portion of GI tract, and liver
With gastroschisis, the loops of bowel are
NEVER covered by membrane
When does umbilical herniation occur?
when the intestines return normally to the abdominal cavity and then herniate either prenatally or postnatally through an inadequatley closed umbilicus
What is an omphalomesenteric cyst?
a cystic lesion of the umbilical cord caused by persistence and dialation of a segment of the omphalomesenteric duct
This omphalomesenteric cyst is found closer to the
fetal insertion and may vary in size
What causes a hemangioma of the cord?
the transepithelial cells of the vessels of the umbilical cord
Sites of origin of hemangiomas of the cord:
main vessels of the cord, may involve more than one.
T/F: Hemangiomas of the cord are rare?
TRUE
Hematoma of the cord is caused by
trauma to vessels resulting in blood moving into Wharton’s jelly..usually occuring near the fetal insertion of cord and the umbilical vein is most often involved.
What is thrombosis of the umbilical vessels?
occlusion of one or more vessels of the umbilical cord
Which vessel(s) is the primary location of thrombosis?
umbilical vein
Thrombosis may be primary or secondary to:
torsion knotting looping compressions or hematoma
T/F: Prognosis is good in the fetus with umbilical vein thrombosis?
False, it’s poor
True knots of the cord have been associated with
long cords Polyhydramnios intrauterine growth restriction monoamniotic twins and increased risk of congenital anomalies
When are false knots found?
When the blood vessels are longer than the cord (often they fold on themselves and produce nodulations on the surface of cord)
The most common cord entanglement in the fetus:
nuchal cord
A single loop of cord has been seen in more than ___% of deliveries, two loops have been found in ___%.
20%, 2.5%
What issues are seen more frequently with fetuses suffering cord entanglement?
fetal heart deceleration
meconium stained amniotic fluid
babies requiring resuscitation
Why is a battledore placenta significant?
When the cord is inserted near the cervical os, labor may cause the cord to prolapse or be compressed during contractions
What occurs when the cord inserts into the membranes before it enters the placenta raither than inserting directly into the placenta?
Membranous/Velamentous insertion
Velamentous insertion MAY occur when?
If most of the placental tissue grows laterally, leaving the initially centrally located cord in an area that becomes atretic.
Velamentous insertion is associated with:
Higher risk of low birth weight Small for gestational age Preterm delivery Low Apgar scores Abnormal intrapartum fetal heart rate pattern
When does prolapse of the cord occur?
when cord lies below presenting part (may occur whenever the presenting part does not fit closely and fails to fill pelvic inlet
Compression of cord may cause
fetal demise (lack of blood supply)
Abnormal fetal presentation occurs in ____ of prolapse cord cases
nearly half
10 conditions predisposing to cord presentation and prolapse:
Abnormal fetal presentation
Nonengagement of the fetus because of prematurity
Long umbilical cord
Abnormal bony pelvic inlet
Leiomyomas
Polyhydramnios
Vasa previa
Velamentous insertion of the cord
Marginal insertion of the cord in a low-lying placenta
Incompetent cervix with premature rupture of the membranes
______ of cord prolapse problems are produced during obstetric procedures
One third (1/3)
What obstetric procedures can cause cord prolapse?
artificial rupture of membranes
disengaging the head
flexion of an extended head
version and extraction
What is the best method of detecting vasa previa?
color Doppler
Define vasa previa
presence of umbilical cord vessels crossing internal os
What factors may cause vasa previa?
velamentous insertion of cord
succenturate lobe
low-lying placenta with marginal insertion near os
Single umbilical arteries have been found in __% of pregnancies with marginal insertion and in __% of those with membranous insertion of the cord.
18%, 9%
Probable cause of single umbilical artery:
atrophy of one during early development stage
Which umbilical artery is most often missing?
Left (just a slightly higher percentage difference)
Single umbilical artery is associated with:
Congenital anomalies in 20-50% of cases
Increased incidence of IUGR
Increased perinatal mortality
Increased incidence of chromosomal abnormalities
Anomalies associated with single umbilical artery that affect other organ systems:
Musculoskeletal Genitourinary Cardiovascular Gastrointestinal Central nervous system
Hypoplastic umbilical artery occurs when
a 3-vessel cord shows an artery-to-artery difference of more than 50%
What is aneurysm of umbilical vessels?
focal dilation of umbilical artery
What is varix?
focal dilation of umbilical vein
How does varix appear sonographically?
a dilated intraabdominal, extrahepatic portion of the umbilical vein
Prognosis of fetus with varix?
normal
Typically, by 6 weeks the right umbilical vein
regresses and the left umbilical vein enlarges to accomodate the increasing flow
When the right umbilical vein does not disappear, this is called:
persistent intrahepatic right portal vein (rare and may be related to an involution of the left umbilical vein)
If right umbilical vein persists, where will it go?
enters the right lobe of liver to join the right portal vein
What % of cases of persistent right portal veins have other fetal anomalies?
at least 50%
Sonographically, what does it look like when the right vein persists?
Vein curves toward the left-sided stomach rather than towards the liver
