[] True knot of the umbilical cord is a rare condition (up to 1.25% of pregnancies (Ref#1)) with the highest rate occurring in monoamnionic twins. It is difficult to diagnose this with prenatal ultrasound because sonographers are not generally looking for this condition. True knots arise from fetal movements and are more likely to develop during early pregnancy, when relatively more amniotic fluid is present and greater fetal movement occurs. Constriction of a true knot is not common but it may lead to obstruction of the fetal circulation and subsequent intrauterine death. In fact, fetuses with true umbilical knots are at a four-fold increased risk of intrauterine death (Ref#2). It has been reported that true knots are associated with the following conditions (Ref#1 and #2):

her comment is here –  Advanced maternal age
–  Multiparity
–  Previous miscarriages
–  Obesity
–  Prolonged gravidity
–  Male fetus
–  Long cord
–  Maternal anemia
–  Maternal chronic hypertension
–  Hydramnios

mobile dating apps for ios Pulsed wave Doppler spectral analysis can be used to demonstrate a stenotic effect on the umbilical venous blood flow post-stenosis (Ref#3). A pre stenotic dilation of the umbilical vein can also be seen. A cesarean delivery may be considered if a diagnosis of a true cord knot is made.
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