Helical structure of the human umbilical cord

Area of Science:

• Developmental Biology
• Human Anatomy
• Biophysics

Background:

• The helical structure of the human umbilical cord is a well-documented anatomical feature.
• Previous studies have shown variations in twist direction and incidence.
• A clear nomenclature for twist direction has been lacking, leading to discrepancies.

Purpose of the Study:

• To investigate the incidence and characteristics of human umbilical cord helical patterns.
• To propose a standardized method for determining umbilical cord twist direction.
• To explore the developmental timing and potential influencing factors of cord coiling.

Main Methods:

• Analysis of 528 full-term umbilical cords from normal deliveries.
• Examination of 18 cords from aborted fetuses (CR length 1.2-19.5 cm).
• Study of 10 umbilical cords from monozygotic twins.
• Development of a novel method to define twist direction based on fetal rotation.

Main Results:

• Right helical patterns occurred in 64.58%, left in 15.15%, and mixed patterns in 17.43% of cords.
• An exponential relationship was observed between the number of twists and the cord's length-to-thickness ratio.
• Umbilical cord twisting initiates in the 8th week of gestation and is likely finalized shortly after the 9th week.
• Absence of concordance in monozygotic twins suggests multifactorial control.

Conclusions:

• A standardized method for assessing umbilical cord twist direction has been proposed.
• The helical structure of the human umbilical cord develops early in gestation.
• Both genetic and environmental factors likely contribute to the formation of umbilical cord twists.