ABNORMALITIES OF CORD COILING 

-         COILING INDEX

-         ABSENT COILING

-         HYPERCOILED CORD

 

Three vessel cord – normal coiling

Two vessel cord – absent coiling

Hypercoiled cord – cord accident in utero 28 wks

 

 

ETIOLOGY OF UMBILICAL VASCULAR COILING

 

Link to Etiology Of Umbilical Vascular Coiling

 

COILING INDEX (1-4)
  • Umbilical coil index (UCI) = the reciprocal distance between a pair of coils.
    • Neonates with nuchal cords = 0.18 ± 0.09 coils / cm.
    • Neonates without nuchal cords = 0.21 ± 0.07 coils / cm.
  • UCI = 0.10 coils / cm - 42% had nuchal cords.
  • UCI ³ 0.30 coils / cm - 4.8% had nuchal cords.

 
  • More coiled cords are less easily wrapped around the fetal neck (1)
  • Assuming an average coiling index of 0.2 coils/cm, there 10-12 vascular coils between fetal and placental insertion sites.
  • May coil from 0-40 twists (0 coils seen in 5% of pregnancies and is associated with an increased fetal morbidity and mortality)
  • Left coiling 87.5%, right coiling 11.8%, <2% both left and right coils. Usually an average of 11 coils throughout its length.
    Left : Right coiling = 7:1.
  • May be seen as early as 6 weeks and is usually well established by 9 weeks, and is thought to enhance its ability to withstand outside forces (tension, compression and stretching).
  • The numbers of twists are thought to be constant throughout the pregnancy (1).

 

Abnormalities Of Umbilical Cord Coiling

Normal cord coiling

 

Absent cord coiling

  • ± 5% of fetuses lack vascular coiling (5).
  • Noncoiled straight cords are at risk for poor perinatal outcome.
    • Stillbirth rate = 8-10%(5-7).
    • Aneuploidy.
    • Meconium staining.
    • Increased incidence of IUGR, oligohydramnios, fetal anomalies, intrapartum fetal heart rate decelerations, meconium stained amniotic fluid, preterm delivery, low umbilical artery pH values and low Apgar scores.

 

 

Excessive cord coiling

  • Excessive coiling has also been associated with adverse outcome.
  • Frequency of as high as 21% (12).
  • Associations include (12-14):
    • Fetal demise.
    • Fetal intrapartum distress.
    • IUGR.
    • Chorioamnionitis.
    • Nuchal cord loops.

 

 

 

 

 

Straight and coiled cord in the same fetus

 

Increased incidence of absent and right coiling associated with single umbilical artery (8). In SUA due to primary agenesis of on artery coiling is usually absent, whereas in SUA due to atrophy of one artery occurs after 42 days of gestation, when cord coiling is already well established (8).

 

Quin et.al. (9) suggests that there is a progressive change in UCI occurring along the length of the cord (and suggests a consistent habit of measuring sequentially in one direction), in addition to the differences observed at the placental and fetal insertions. They suggest that umbilical coiling does alter after the initial formation of coils in the first trimester.

·        Left-handed coiling occurred six to seven times as frequently as right-handed

·        Mixed patterns occurred in about 25% of our cases.

·        Coiling direction did change after our ultrasonic examination in one-quarter of cases in one series.

·        Reversals of coiling may occur several times in the same cord, while straight segments may also occasionally intervene between portions that are otherwise normally coiled.

·        UCI has two components, the number of coils and the overall length of the umbilical cord. There was a linear correlation between the length of cord and the number of coils in one study (9), however hypercoiling per se was not associated with long cords. This tendency has been reported before and is thought to relate to increased fetal activity amongst male infants.

·        It has been suggested that performing ultrasound earlier ( between 12 and 16 weeks of gestation), may be helpful in identifying straight and hypocoiled umbilical cords as it is unlikely that significant coiling will develop later in gestation (9) (hypocoiling has been shown to be predictive for the development of intrauterine growth restriction) (10). However, the sensitivity for detection of hypercoiling would decrease as the majority of cords exhibit hypercoiling at this earlier gestation.

·          The identification of hypocoiled cords is also of relevance in later pregnancy as they are associated with a higher incidence of tight nuchal cord entanglement than those with a normal UCI, which can lead to oxidative stress in the neonate (11).

 

 

REFERENCES
  1. Malpas P, Symonds EM. Observations on the structure of the human umbilical cord. Surg Gynecol Obstet 1966;123:746-750.
  2. Strong TH, Jarles DL, Vega JS et.al. The umbilical cord coiling index. Am J Obstet Gynecol 1994;170:29-32.
  3. Rana J Ebert GA, Kappy KA. Adverse perinatal outcome in patients with an abnormal umbilical coiling index. Obstet Gynecol 1995;85:573-577.
  4. Strong TH, Manriquez-Gilpin MP, Gilpin GP. Umbilical vascular coiling and nuchal entanglement. J Maternal Fetal Med 1996;5:359-361.
  5. Strong TH, Finberg HJ, Mattox JH. Antepartum diagnosis of noncoiled umbilical blood vessels. Obstet Gynecol 1994;170:1729-1733.
  6. Strong TH, Elliott JP, Radin TG. Noncoiled umbilical blood vessels: A new marker for the fetus at risk. Obstet Gynecol 1993;81:409-411.
  7. Strong TH. Trisomy among fetuses with noncoiled umbilical vessels. J Reprod Med 1995;40:789-790.
  8. Lacro RV, Jones KL, Benirschke K. The umbilical cord twist: Origin, direction and relevance. Am J Obstet Gynecol 1987;157:833-838.
  9. Y. Qin, T.K. Lau, M.S. Rogers. (2002) Second-trimester ultrasonographic assessment of the umbilical coiling index. Ultrasound in Obstetrics and Gynecology 2000:20:458-463.
  10. Degani S, Leibovich Z, Shapiro I, Gonen R, Ohel G. Early second-trimester low umbilical coiling index predicts small-for-gestational-age fetuses. J Ultrasound Med 2001; 20: 1183-1188
  11. Wang CC, Rogers MS. Lipid peroxidation in cord blood. Effects of umbilical nuchal cord. Br J Obstet Gynaecol 1997; 104: 251-255
  12. Machin GA, Ackerman J, Gilbert-Barness E. Abnormal umbilical cord coiling is associated with adverse perinatal outcomes. Pediatr Dev Pathol 2000 Sep-Oct;3(5):462-471
  13. Herman A, Zabow P, Segal M, Ron-el R, Bukovsky Y, Caspi E. Extremely large number of twists of the umbilical cord causing torsion and intrauterine fetal death. Int J Gynaecol Obstet 1991 Jun;35(2):165-167.
  14. 124 Strong TH Jr, Manriquez-Gilpin MP, Gilpin BG. Umbilical vascular coiling and nuchal entanglement. J Matern Fetal Med 1996 Nov-Dec;5(6):359-361