The cord diameter increases with gestational age and fetal
growth. An abnormally narrow umbilical cord correlates with small infant size or low birth weight. Cord diameters of less
than 0.8 cm in term infants correlate with utero-placental ischemia. The difference in cord diameters can be striking when
examining a twin placenta with birth weight discordance. There is insufficient evidence to implicate a narrow cord per se
A uniformly thick
cord with just more Wharton’s jelly or more hydration is not known to be harmful, but the cause is unknown. There
may be thickening with fetal hydrops, but since there is no capillary bed in the umbilical cord, it is not very sensitive
to hemodynamic changes. Sometimes cords of unexplained stillborn infants appear unusually thick.
can be due to underlying pathology such as tumor, hematoma, or vascular aneurysm. These will be discussed separately. An unusual
but clinically important cause of umbilical cord thickening at the fetal end is urination into the cord through a patent urachus.
In the one case I saw, there was also urethral obstruction.
The diameter and cross sectional shape vary along the length of the umbilical cord. A mean diameter can still be estimated.
Cords less than 0.8 cm or more than 1.5 cm may correlate with fetal growth retardation or macrosomia respectively. Long term
follow-up studies are needed to determine if the cord diameter has any independent significance. Clinically significant pathology
is most likely to be found in focal thickening greater than 2 cm diameter. Focal lesions are often discolored red or clear
as in necrotizing funisitis.
Cord diameter in first trimester
An ultrasound study of umbilical cord diameter in 439 fetuses between 8-15 weeks of gestation demonstrated a linear
increase of diameter with gestational age, crown rump length and biparietal diameter1. At 8 weeks the mean diameter
was 2.74±0.43 compared to 5.16±0.59 at 14 weeks of gestation. They found that some fetuses with smaller cords had fetal demise
or subsequent development of preeclampsia, but did not have the power to find a significant association. They note that the
diameter of the cord in early gestation is more due to vessel diameter than the small amount of Wharton’s jelly.
The same authors used normative umbilical cord diameter from 10-14 week to compare aneuploid fetuses with normals2.
They found a significant percentage of aneuploid fetuses with diameters greater than the 95th percentile (approximately
30% of fetuses with diameters above 95th percentile had aneuploidy, which was 5 cases from a total of 784 measured
cords). The authors speculate whether this was due to alterations in chemical composition of Wharton’s jelly or congestion
and enlargement of the umbilical vein.
An ultrasound study of 299, 11-14 weeks of gestation fetuses demonstrated an increasing diameter of the cord with both
gestation and crown rump length. The diameters ranged between 2.7 and 5.1 mm except for a 2.2 and a 6.5 mm outlier. Significantly
more aneuploid fetuses had diameters above the 95th percentile compared to euploid3.
A study of umbilical cord areas (measured at insertion into the fetal abdomen) measured after 20 weeks of gestation
found that infants with birth weights for gestation below the 5th percentile had significantly more umbilical cord
areas below the 10th percentile4. There was no increase in the umbilical cord area after 32 weeks of
gestation. In 403 patients with measurements between 31 and 42 weeks of gestation there was a correlation of umbilical cord
area with birth weight (r = 0.37).
Umbilical cord edema
A 1975 study of 100 umbilical cords found that cord edema defined as a maximum cross sectional area of 1.3 cm2
(measured as the product of two cross sectional diameters) occurred in 10% of placentas5. The authors found 15
of 50 Rhesus iso(allo)immunization, 15 of 24 abruptio placenta, 19 of 25 macerated stillbirths, and 7 of 17 diabetic infants
had umbilical cord edema. All were a statistically significant compared to the control incidence. They did not to record infant
hydrops, nor measure water content of the cord. The authors comment that of the abruptio placentas, cord edema occurred generally
in the stillborn infants with large retroplacental hematomas. They did not record
birth weight of the diabetic cases. As a result some correlation may be due to hydrops or macrosomia. The correlation of cord
edema with stillbirth was not further developed.
A study from the same group further studied umbilical cord edema by comparing weight before and after freeze drying
(N=57) and by microscopic sterology of intercepts on tissue and on empty spaces (N=28)6. As before, they used 1.2
cm2 as a cut off between normal and edematous cords. They found are general correlation of thick cords with higher
water content. There were three cords that were thick but had extraordinarily low water content, a result that was discarded
as probably error. They also found three thin cords that had high water content. One had a tight nuchal cord and fetal anemia;
another had R hallo-immunization, and the third was a twin. The quantitative histology confirmed more open spaces in the thicker
cords. The wet thin cords fell between these and the normal and thin cords.
In an in vitro study of the perfused umbilical cord, intravascular
vascular endothelial growth factor did result in edema in the wall of the umbilical vein7. This result suggests
that increased endothelial permeability over time might lead to edema of Wharton’ jelly.
Leakage of urine into Wharton’s jelly from a patent urachus has been reported multiple times8, 9.
A case of a patent urachus with an umbilical cord diameter of 4.5 cm prompted the authors of a paper to infuse solutions of
different osmolarity into human umbilical cords at 135 cm of water pressure8. Hypertonic solutions did not produce
edema but exuded from the surface, while hypotonic solutions did cause swelling, although at a lesser degree than in the clinical
Morphological studies of Wharton’s jelly have not added much insight into cord width. In pre-eclampsia this is
a loss of hyaluronic acid compared to sulfated glycoaminoglycans10. An SEM study of the collagen fiber skeleton
of Wharton’s jelly demonstrates the lattice type appearance that can easily be seen in microscope slides11.
This lattice appearance was confirmed in an immunohistochemical and ultrastructural study12. This study also documented
the progression over gestation of the maturation of stromal cells toward myofibroblasts. In intrauterine growth retardation
there is a decrease in the cross sectional area of Wharton’s jelly as well as the umbilical vein and its lumen13.
In cases of growth retardation with abnormal end diastolic flow on Doppler studies, there is also a reduction in arterial
area and wall thickness.
Ghezzi F, Raio L, Di Naro E, et al. First-trimester sonographic umbilical cord diameter and the growth of the human
embryo. Ultrasound Obstet Gynecol 2001;18(4):348-51.
Ghezzi F, Raio L, Di Naro E, Franchi M, Buttarelli M, Schneider H. First-trimester umbilical cord diameter: a novel
marker of fetal aneuploidy. Ultrasound Obstet Gynecol 2002;19(3):235-9.
Axt-Fliedner R, Schwarze A, Kreiselmaier P, Krapp M, Smrcek J, Diedrich K. Umbilical cord diameter at 11-14 weeks of
gestation: relationship to nuchal translucency, ductus venous blood flow and chromosomal defects. Fetal Diagn Ther 2006;21(4):390-5.
Raio L, Ghezzi F, Di Naro E, et al. Prenatal diagnosis of a lean umbilical cord: a simple marker for the fetus at risk
of being small for gestational age at birth. Ultrasound Obstet Gynecol 1999;13(3):176-80.
Coulter JB, Scott JM, Jordan MM. Oedema of the umbilical cord and respiratory distress in the newborn. Br J Obstet
Scott JM, Wilkinson R. Further studies on the umbilical cord and its water content. J Clin Pathol 1978;31(10):944-8.
Infanger M, Grosse J, Westphal K, et al. Vascular endothelial growth factor induces extracellular matrix proteins and
osteopontin in the umbilical artery. Ann Vasc Surg 2008;22(2):273-84.
Tsuchida Y, Ishida M. Osmolar relationship between enlarged umbilical cord and patent urachus. J Pediatr Surg 1969;4(4):465-7.
Chantler C, Baum JD, Wigglesworth JS, Scopes JW. Giant umbilical cord associated with a patent urachus and fused umbilical
arteries. J Obstet Gynaecol Br Commonw 1969;76(3):273-4.
L, Bankowski E, Jaworski S. The activities of some glycosaminoglycan-degrading enzymes in the wall of the umbilical cord artery
and their alteration in edema, proteinuria, hypertension (EPH)-gestosis. Clin Chem Lab Med 1999;37(4):417-21.
E, Correr S, Goranova V, et al. The collagen skeleton of the human umbilical cord at term. A scanning electron microscopy
study after 2N-NaOH maceration. Reprod Fertil Dev 1996;8(5):885-94.
AK, Kohnen G, Milovanov AP, Domogatsky SP, Kaufmann P. Stromal differentiation and architecture of the human umbilical cord.
JF, Sibony O, Benali K, Challier JC, Blot P, Nessmann C. Computerized microscope morphometry of umbilical vessels from pregnancies
with intrauterine growth retardation and abnormal umbilical artery Doppler. Hum Pathol 1997;28(10):1139-45.