Significance of the umbilical cord: the umbilical cord can be aptly termed the life line for the fetus during its intrauterine life but can often be the cause for its misery in case of cord pathology.
Coiling of the umbilical cord:
Medical literature describes the normal coiled nature of the cord containing the umbilical vein and two umbilical arteries with Wharton’s jelly as the connective tissue. The first mention of the coiled nature of the cord was by Berengarius in 1521. Later, Edmonds used the term “Index of twist” to describe the measure of twisting or coiling of the cord (1954).
Umbilical coiling index (UCI):
The term “Umbilical Coiling Index” was introduced more recently. During the prenatal period, the UCI is obtained (using sonography) by the reciprocal of the distance between two umbilical coils (the intercoil distance in centimeters). In other words, UCI = 1/intercoil distance in centimeters.
After delivery, the UCI is measured by dividing the total number of coils by the total length of the cord in centimeters. Since the current discussion relates to the sonographic aspects of the coiling of the cord, we shall use the prenatal estimation of the UCI.
What is hypocoiling of the cord?
The term “hypocoiling of the cord” refers to abnormal decrease in the coiling of the umbilical cord. This is defined as UCI less than the 5th percentile for the gestational age of the fetus. In practical terms the normal range of UCI= 0.20 +/- 0.1 (Ercal et al). When the intercoil distance increases, the lower the value of the UCI and more severe is the hypocoiling of the cord.
This 28 week old pregnancy (images below) shows a typical hypocoiled cord.
Click to enlarge image
Image-1: Hypocoiled cord in 28 week old gestation:
Image-2: color Doppler study:
What are the causes of coiling of the cord:
The normal cord contains two umbilical arteries and a vein spiraling around Wharton’s jelly a viscid substance present in the cord. Many studies of the jelly show the crucial role played by the chemical composition of Wharton’s jelly in cord coiling, especially the role of a compound called hyaluronan. Hyaluronan is believed to aid in the growth of the umbilical vessels and subsequent coiling. The role of both genetic and acquired factors such as fetal movements in the normal coiling of the cord cannot be underestimated.
What is the significance of hypocoiling of the cord?
A few studies have been done and described in literature pertaining to prenatal sonographic diagnosis of hypocoiling and its impact on fetal morbidity and mortality. These studies all point to increased incidences of the following conditions associated with cord hypocoiling: fetal distress, oligohydramnios, preterm delivery, growth retardation, meconium staining during delivery, fetal heart rate alterations, low cord pH, etc. Other researchers have found an association between hypocoiled cords and fetal trisomy 21. In any case, all cases of hypocoiled cord discovered on sonography, must be followed closely and repeatedly to exclude and prevent fetal morbidity and mortality.