False vs. True Umbilical Cord Knot

Introduction

1. Umbilical cord length varies from achordia to 300cm, diameters up to 3cm.

2. Helical in nature with as many as 380 helices.

4. Avarage umbilical cord is 55cm, 1-2cm in diameter and 11 helices.

5. Most cord coils to left with unknown reason

6. 5% of cord shorter than 35 cm and 5% longer than 80 cm.

7. Short cord a/w fetal movent disorder, intrauterine constrain, placental abruptio and cord rupture.

8. Long cord a/w fetal entanglement, true knot and thrombi.

True knots

©1993 – 2010 by The University of Utah • Spencer S. Eccles Health Sciences Library, image taken from this [link]

1. Complicates 1% of pregnancy with highest rate occuring in monoamniotic twin.

2. Arise from fetal movement and more likely to develop during early pregnancy (more amniotic fluid and greater fetal movement)

3. Also could associated with abnormally long umbilical cord, advanced maternal age and multiparity.

4. May lead to up to a 4 fold increase of fetal loss (about 10% of fetal mortality)

5. Umbilical cord is tied in a true knot

6. May be loose or thight

7. Loose knot did not affect circulation (no color changes or swellings)

8) Thight knot (affect circulation, lead to hemorrhage on the fetal side of knot and edema on the placental site). It also can cause compression of Wharton's jelly and mural thrombosis in umbilical vessel

False knot

1. Of no clinical importance and it is actually kinks in the cord due to tortuous aggregation of dilated ectatic vessel with less covering of Wharton's jelly.

Image taken from this [link]

Notes:

1. Wharton's jelly (substantia gelatinea funiculi umbilicalis) is a gelatinous substance within the umbilical cord, largely made up of mucopolysaccharides (hyaluronic acid and chondroitin sulfate). It also contains some fibroblasts and macrophages. It is derived from extra-embryonic mesoderm.[Wikipedia]

2. Ectasia is a pathologically explaination for distension or dilation of a duct, vessel, or hollow viscus

Reference

1. Linda Ernst, "Umbilical Cord Knot", http://radiology.uchc.edu/eAtlas/GYN/405.htm

2. Marie Helen Beall, "Umbilical Cord Complications" http://emedicine.medscape.com/article/262470