Sonographic incidence of uncoiled umbilical cords during the entire gestation

Introduction

Pathology studies have reported that uncoiled umbilical cords (UC) are frequently present in certain conditions such as miscarriage, unexplained fetal death, aneuploidies, structural abnormalities and fetal distress. Therefore, it would be important to analyse UC angioarchitecture during antenatal sonography. However, no information is available on the sonographic incidence of such UC's in otherwise normal pregnancies.

Materials and Methods Consecutive women with singleton gestation and with a normal fetus were eligible for the study. Each women was included only once. Color flow mapping was used to enhance the definition of the umbilical cord vessels. An UC was defined uncoiled in the presence of two straight umbilical arteries. The incidence of uncoiled UC's was calculated by two weekly intervals. Spearman rank correlation was used for statistical purposes.

Results

A total of 340 women at a median (range) gestational age of 17.5 (7.2–40.1) weeks were enrolled. Overall incidence of uncoiled UC's was 13.5%. A significant correlation was found between gestational age and incidence of uncoiled UC's (r=–0.65 [95%CI –0.87 to –0.23]; p<0.01). Below 8 weeks of gestation 85.7% of cases showed an uncoiled cord. This incidence sharply decreases with advancing gestation and after 14 weeks only 9.6±5.8% of UC's were classified as uncoiled.

ConclusionsMorphology of UC shows marked changes depending on gestational age. This is particularly true for the first trimester of gestation in which the UC vessel changes rapidly from a predominantly parallel to the typical twisted appearance. It is interesting that this sort of maturation of the UC morphology occurs with other important events such as the formation of the intervillous space and the appearance of diastolic Doppler flow velocities within the UC arteries.