The natural history of antenatal nuchal cords

OBJECTIVE: 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. STUDY DESIGN: 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 weeksʹ 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. RESULTS: 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. CONCLUSION: 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.