RESUMO
BACKGROUND: To investigate the intrapartum factors related to umbilical cord nuchal loops (nuchal cord) with particular reference to shoulder dystocia. METHODS: We studied all singleton pregnancies with a vertex presentation and a birth weight of at least 2500 g from 1 January 1978 to 31 March 1997 and the 13,717 pregnancies with nuchal cord were compared to the 44,136 without nuchal cord. RESULTS: When compared to pregnant women without nuchal cord, a greater proportion of pregnant women with nuchal cord underwent induction of labor (adjusted OR 1.09, 95% CI 1.04-1.15) and augmentation with oxytocin (adjusted OR 1.06, 95% CI 1.01-1.11). They had a longer second stage of labor (p=0.0013) and a greater proportion of primiparous women with tight nuchal cord had second stage of labor that lasted longer than two hours (adjusted OR 1.21, 95% CI 1.03-1.41). The proportion of abnormal fetal heart rate patterns was higher in the presence of nuchal cord (adjusted OR 1.61, 95% CI 1.55-1.68). Shoulder dystocia occurred more commonly in association with nuchal cord, especially when the nuchal cord was tight (adjusted OR 1.50, 95% CI 1.30-1.72 for all nuchal cord; adjusted OR 1.82, 95% CI 1.42-2.34 for tight nuchal cord). CONCLUSIONS: Umbilical cord nuchal loops are associated with induction of labor, slow progress of labor, and shoulder dystocia.