A
nuchal cord occurs when the
umbilical cordIn placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
becomes wrapped around the fetal neck 360 degrees.
- A "Type A" nuchal cord is wrapped around the neck 360 degrees.
- A "Type B" pattern is described as a hitch which cannot be undone and ends up as a true knot.
In 1962 J.Selwyn Crawford MD from the British Research Council defined nuchal cord as 360 degrees around the fetal neck.
A
nuchal cord occurs when the
umbilical cordIn placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
becomes wrapped around the fetal neck 360 degrees.
Classification
- A "Type A" nuchal cord is wrapped around the neck 360 degrees.
- A "Type B" pattern is described as a hitch which cannot be undone and ends up as a true knot.
Diagnosis
In 1962 J.Selwyn Crawford MD from the British Research Council defined nuchal cord as 360 degrees around the fetal neck. Dr Crawford commented " It is all the more remarkable,therefore, that little work has been done---to analyze its effects during labor and delivery". To date there is no prospective case control double blind study looking at the issue of nuchal cord.Observational studies vary in opinion as to the degree of poor outcomes with the error of not including both Type A and B nuchal cord forms .Also not included in these studies is which umbilical cord form (there are 8 different structures) was in a nuchal cord form. These oversights invalidate any study to date. The impact of Nuchal Cord on the fetus is unknown.
Ultrasound diagnosis of a cord around the neck was first described in 1982. “Coils occur in about 25% of cases and ordinarily do no harm, but occasionally they may be so tight that constriction of the umbilical vessels and consequent hypoxia result.” Williams Obstetrics 16th Edition, has only one single sentence in the entire textbook regarding cords around the neck:
(P.421) By contrast , the First Edition of the Encyclopedia Britanica from 1770 had 20 pages of information about Umbilical Cord Pathology with drawings of Umbilical Cord Entanglement. The Royal College of OBGYN has these images on its brochure. There are currently three recent texts on Ultrasonography which demonstrate the ability of ultrasound to identify umbilical cord issues with reliability as of 2009.
A study published in 2004 was done to establish just how sensitive ultrasound is in diagnosing a nuchal cord. Each of 289 women, who were induced the same day, underwent a transabdominal ultrasound scan with an Aloka 1700 ultrsound machine with a 3.5 MHz abdominal probe, using gray-scale and color Doppler imaging immediately prior to induction of labor. Presence of the cord was sought in the transverse and sagittal plane of the neck. A nuchal cord was diagnosed if the cord was visualized lying around at least 3 of the 4 sides of the neck. A cord was actually present at delivery in 52 of the 289 women. Only 18 of the 52 cords or 35% of the nuchal cords were detected on ultrasound done immediately before delivery, and 65% of nuchal cords were not detected. Of the 237 cases where there was no cord at delivery, ultrasound had false positive results, ie. diagnosed a cord in 44 of the 237 cases (19%) in which there was no cord present at all.
In this study, ultrasound was only 35% accurate at finding a single loop, and only 60% accurate at detecting a nuchal cord wrapped multiple times around the neck.
In no study was it possible by ultrasound to distinguish between a loose or a tight cord on ultrasound, although at least 3 attempted to do so. Peregrine concludes that ultrasound diagnosis of nuchal cords will only be useful if we are able to do so reliably and predict which of those fetuses are likely to have a problem., However, perinatologists routinely look for umbilical cord issues in monoamniotic twins. Studies have shown an improvement in outcomes where cord entanglement was prenataly identified in these cases. Ultrasound measurement of the velocity of flow in the cord may be useful in the management of twins and chronically growth-retarded fetuses.Of course this depends on the training of the sonographer . To date there are no ultrasound courses which teach the identification of nuchal cord to physicians or technicians.A recent review by Wilson of the American Academy of Ultrasonography Technicians recommends the documentation of umbilical cord issues.
Clapp attempted to find out at what rate nuchal cords come and go during pregnancy. He recruited 84 healthy, non-smoking, non-substance abusing women carrying a single fetus, with certain dates before the 20th week of gestation. They all agreed to 4 extensive ultrasounds at 24-26, 30-32, 36–38 weeks gestation and during labor and delivery- evaluating:
Fetal biometry
Fetal tone
Fetal motion including breathing movements
Amniotic fluid volume
Fetal Flow Redistribution
Velocity flow profiles from the umbilical artery at the body wall and placental insertion and at the origin of fetal middle cerebral artery.
Finally, color flow Doppler imagine was used to determine whether a nuchal cord was present. Clapp reports that 60% or in 50 of the 84 fetuses studied a nuchal cord was seen on ultrasound at one of the 4 evaluations. He found that the presence of a nuchal cord linearly increases as the pregnancy continues. See table below. The presence of nuchal cord rose with advancing gestation. Larson found this to be true. He found of the 13,895 singleton deliveries, a nuchal cord linearly increased every week of gestation, appeared in 6% at 20 weeks to 29.0% at 42 weeks' gestation.
Prognosis and treatment
Retrospective data of over 182,000 births, with the statistical power to determine even mild associations, proved conclusively, that a single or multiple nuchal cords at the time of delivery is not associated with adverse perinatal outcomes, is associated with higher birthweights and less cesarean sections in births. Nuchal cord does not need any additional obstetrical intervention unless there is evidence of fetal compromise. The most common clinical sign of fetal effects are fetal heart rate decelerations during labor or a change in fetal behavior prenatally.A recent study by Onderoglu et al. demonstrates nuchal cord can have fetal effects. A recent article by Hasagawa recommends the evaluation and management of umbilical cord pathology.
Checking for the presence of a nuchal cord is the second step in delivering a newborn. During a cephalic delivery, after the head presents the first step is to support the head and then use the middle finger to check for the presence of a nuchal cord. If one is discovered, an attempt to unwrap the cord is made. If the nuchal cord is wrapped too tightly around the newborn's neck and cannot be corrected, old protocols said to clamp the cord in two places and carefully cut to relieve the tension. (Emergency Care in the Streets(Textbook)) The latest research shows that there is little reason to check for a cord, because cutting it cuts off the oxygen that the placenta is supplying and outcomes are better if the baby is delivered, the cord then is no longer compressed after the birth and will continue to provide oxygen for a few more minutes.
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