Knots of the
umbilical cord are classified as true and false. True knots occur in 1% of singleton pregnancies and can be a complication of monochorionic monoamniotic twin pregnancies . Surprisigly , such are rarely detected
on prenatal US. They may form as
a result of torsion of the cord forming a loop through
which the fetus may slip forming
a knot . The term false knots
is a misnomer because they
represent a focal redundancy of the
vessels that can appear
sonographically as a
vascular protuberance simulating a knot . The key feature is that
the USG appearance does not persist in
all scanning planes.
Nuchal
Cord
Nuchal cords
the term used to describe entanglement of the umbilical cord around the fetal
neck have been reported in approximately
25% of pregnancies with an incidence ranging between 16% and 30% . They are frequently noted in many otherwise
normal uncomplicated pregnancies with uneventful deliveries in the vast
majority of cases and they are rarely
associated with perinatal morbidity or
mortality . But they have been
considered worrisome for
possible associated fetal injury particularly when there are two or more
tight loops around the fetal neck.
Some are of opinion that nuchal cords were implicated in the
intrauterine deaths of three term fetuses who had presented with decreased fetal
movements but with normal amniotic fluid volume fetal size and umbilical artery
Doppler findings before delivery.
To mention or not to mention about presence Nuchal
cords in report page by the concerbed sonologist , more so if one loop is
around the neck ?? How to counsel the woman
at third trimester?? Should it by itself be an indication for CS??
A single
loop of umbilical cord seen near the fetal neck is most often an incidental
finding and not associated with fetal risk. N cord may be recognized on prenatal USG with
many published reports of this observation. They are recognized
sonographically as two adjacent loops
of cord in cross section posterior to the neck best appreciated with Color Doppler. Antenatal
nuchal cords usually occur randomly with increased frequency later in gestation.
It has been noted that nuchal cords
seen by US early in pregnancy may spontaneously reduce during
gestation.
Two
knots or > 2 knots –Foetal outcome: The question of whether or not nuchal cords
are associated with significantly increased adverse fetal outcome is rather controversial and remains
unclear despite many investigations. It has been suggested that the observation of
a nuchal cord is of greater concern when seen in association with other findings specifically decreased amniotic
fluid volume growth restriction post dates and especially decreased fetal
movements. In my opinion sonologists should ideally submit that nuchal cords
should be sought routinely and mentioned in report page. Because in some cases
prompt further evaluation with antenatal testing close surveillance and possible
intervention .
How
relevant is Nuchal cord?? Ans: opinion is divided .Many investigators,
however feel that antenatal nuchal cores
as observed in USG are rarely
associated with perinatal
complications. A study of the utility of US in assessing for nuchal cords in
term of post term pregnancies at the
time of induction found that the sensitivity of US in their detection was low and fetal outcome and
clinical management was not significantly altered by the information arguing against searching
for or reporting this finding. In one
series nuchal cord was present at 18% of deliveries. The sensitivity of US in the diagnosis of nuchal
cords was only 37.5% before induction of
labor at term. Nuchal cord was not associated with increased risk
of cesarean section or poor neonatal outcome
nd did not alters or influence
clinical management at time of delivery.
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