The natural history of antenatal nuchal cords

The purpose of this study was to test the null hypotheses that nuchal cords occur with equal frequency throughout gestation, the presence of an antenatal nuchal cord is usually a random or chance event, nuchal cords do not usually persist, and nuchal cords do not usually produce evidence of acute fetal compromise before labor.

A prospective subject-, examiner-, and physician-blinded study design was used. The fetuses were examined serially at 24 to 26, 30 to 32, and 36 to 38 weeks' gestation and during labor and delivery. Measurements included: ultrasonic or visual detection of nuchal cords and assessment of fetal and neonatal well-being by using standard clinical techniques.

The incidence of nuchal cord rose with advancing gestation from 12% at 24 to 26 weeks to 37% at term. However, at each gestational age, its occurrence was a random or chance event and was not associated with clinical evidence of fetal compromise before labor.

Antenatal nuchal cords usually occur randomly with increased frequency in late gestation and appear to be a normal part of intrauterine life that is rarely associated with perinatal morbidity and mortality.