Clinical significance of true umbilical knots: a population-based analysis.

The objective of this study is to determine the risk of adverse pregnancy outcomes resulting from a true umbilical knot. We analyzed 288 singleton pregnancies with a true umbilical knot among the women who gave birth at Kuopio University Hospital from January 1990 to December 1999. Logistic regression analysis was used to compare pregnancy outcomes of the affected cases with those of the general obstetric population (n = 23,027). The incidence of true knot was 1.25% and it was associated with advanced maternal age, multiparity, previous miscarriages, obesity, prolonged gravidity, male fetus, long cord, and maternal anemia. The women having a fetus with a cord knot underwent cesarean delivery less frequently than unaffected controls. Fetal death and low Apgar score at 1 min occurred significantly more frequently in the study group than in the general obstetric population, the adjusted odds ratios being 3.93 (95% CI, 1.41-11.0) and 1.73 (95% CI, 1.10-2.72), respectively. Otherwise, the pregnancy outcome measures were comparable in the two groups. Fetuses with true umbilical knots are at a four-fold increased risk of stillbirth, but little can be done to prevent fetal deaths during pregnancy. Surviving fetuses with true knots are likely to suffer temporary distress during delivery, but affected newborns recover soon after birth. Thus, monitored vaginal delivery appears to be a safe option for fetuses with true knots.