To date, there is no prospective case control double-blind study looking at nuchal cords and observational studies vary in opinion as to the degree of poor outcomes. Also not included in these studies is which umbilical cord form (of the 8 different possible structures) was considered a nuchal cord.Ultrasound diagnosis of a cord around the neck was first described in 1982. “Coils occur in about 25% of cases and ordinarily do no harm, but occasionally they may be so tight that constriction of the umbilical vessels and consequent hypoxia result.” Williams Obstetrics 16th Edition, has only one single sentence in the entire textbook regarding cords around the neck. By contrast, the First Edition of the Encyclopædia Britannica from 1770 had 20 pages of information about Umbilical Cord Pathology with drawings of Umbilical Cord Entanglement. The Royal College of Obstetricians and Gynaecologists has these images on its brochure. There are currently three recent texts on ultrasonography which demonstrate the ability of ultrasound to identify umbilical cord issues with reliability as of 2009.A study published in 2004 was done to establish the sensitivity of ultrasound in the diagnosis of a nuchal cord. Each of 289 women, induced the same day, underwent a transabdominal ultrasound scan with an Aloka 1700 ultrasound machine with a 3.5 MHz abdominal probe, using gray-scale and color Doppler imaging immediately prior to induction of labor. Presence of the cord was sought in the transverse and sagittal plane of the neck.
A nuchal cord was diagnosed if the cord was visualized lying around at least 3 of the 4 sides of the neck. A cord was actually present at delivery in 52 of the 289 women. Only 18 of the 52 cords or 35% of the nuchal cords were detected on ultrasound done immediately before delivery, and 65% of nuchal cords were not detected. Of the 237 cases where there was no cord at delivery, ultrasound had false positive results, i.e. diagnosed a cord in 44 of the 237 cases (19%) in which there was no cord present at all. In this study, ultrasound was only 35% accurate at finding a single loop, and only 60% accurate at detecting a nuchal cord wrapped multiple times around the neck.In no study was it possible by ultrasound to distinguish between a loose or a tight cord, although at least 3 attempted to do so. Peregrine concludes that ultrasound diagnosis of nuchal cords will only be useful if doctors are able to do so reliably and predict which of those fetuses are likely to have a problem., However, perinatologists routinely look for umbilical cord issues in monoamniotic twins. Studies have shown an improvement in outcomes where cord entanglement was prenatally identified in these cases. Ultrasound measurement of the velocity of flow in the cord may be useful in the management of twins and chronically growth-retarded fetuses. Of course this depends on the training of the sonographer.