A comparison of umbilical cord blood gas values between newborns with and without true knots

Objective: To compare umbilical cord blood gas values in newborns with and without true knots, and to assess the potential impact of true knot formation on cord blood gases. Methods: Twelve newborn infants with true umbilical cord knots were identified and compared with a random control population of 104 newborn infants without true knots. The two groups were analyzed for 11 maternal-fetal variables to determine if they were comparable. Subsequently, the principal outcome variable of the study was evaluated: a comparison between the umbilical arterial and venous blood gas results of the true knot and control populations. Results: The true knot and control populations were comparable with respect to the maternal-fetal variables analyzed. The umbilical cord blood gas values did not differ between groups, except for a slightly lower umbilical artery bicarbonate value in the control group (22.0 mEq/L) versus the true knot group (24.5 mEq/L), P = .025. There was no significant difference in the incidence of acidemia (umbilical artery pH less than 7.20) between the two groups. Conclusion: The presence of true umbilical cord knots does not alter the incidence of umbilical artery acidemia or change umbilical cord blood gas values. Review of the pertinent obstetric literature supports the hypothesis that true umbilical cord knots lack clinical significance.