The impact of true knot of umbilical cord on obstetric outcomes—true or not?

Objectives: To quantify the risk of true cord of the umbilical cord for perinatal death and identify additional risk factors. Methods: This retrospective study included singleton deliveries between 24 and 42 weeks of gestation that took place between 2003 and 2017 in two medical centers. For patients with true knot, data regarding the number of cord knots as well as the location and number of loops of cord were obtained. The rest of the birth data set comprised the control group. The primary outcome was fetal demise. Secondary outcomes included mode of delivery and perinatal outcomes. Results: The final data set included 139,458 deliveries, of which 364 cases (0.26%) comprised the study group (true knot group) and 139,094 cases (99.74%) the control group. Higher rated of unfavorable outcomes were found among cases than controls, including perinatal death, delivery mode, lower Apgar and cord blood umbilical artery pH as well as higher rates of NICU admission and perinatal death. Multivariate analysis showed that true knot of cord (aOR 15.46, 95% CI 9.30–25.70) was a strong predictor of perinatal death. Analysis of predictors of perinatal death within the study group showed that only four or more nuchal loops of cord was an independent predictor (four loops OR 13.40 95% CI 1.12–160.34). Conclusions: True knot of the umbilical cord is a strong predictor of perinatal death. Fetuses with true knot of cord and four or more nuchal cord loops are at significantly increased risk of perinatal death. If diagnosed before onset of labor, delivery before 37 weeks may prevent perinatal death.