The Pregnancy Institute - The Human Umbilical Cord

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The human umbilical cord
Back to Index Go to References Page NEXT - The Perinatal Umbilical Cord Project Disruption of the umbilical cord may be a source of harm to the developing fetus. (1) An estimated 30% of pregnancies carried to term have some type of umbilical-placental abnormality. How these findings affect the fetus and to what degree is unknown. The most obvious unwanted effect of umbilical cord disruption is stillbirth. A review of stillbirth literature from 1930-98 suggests that 15% of all stillbirths with an identifiable cause were associated with umbilical cord complications.(2) Although difficult to prove in humans, Umbilical cord complications are not uncommon in mammals, especially horses.(3) Umbilical cord complications occur throughout pregnancy. Javert and Barton reviewed 1000 cases of spontaneous abortion and reported that 56% had umbilical cord complications while controls had only 6%. (4) These authors noted that 'most of the cord complications were such as to compromise the fetal circulation so as to cause death in utero'. Frkovic et al. reviewed stillbirth between 20 and 36 weeks of gestation, of which 5.4% were associated with umbilical cord complications.(5) Defining the cause of death with supporting evidence varies greatly from country to country. Wang et al. describe a case of stillbirth where the diagnosis of umbilical cord complications is made based on careful pathologic observations.(6) Although the stillbirth did not have delivery evidence of cord entanglement, autopsy findings suggested entaglement and cord compression as the cause of death. Part of the difficulty in determining the cause of death is that the event of delivery itself can undo the puzzle of umbilical cord complications. Delivery can also confuse the statistics of umbilical cord complications by creating false impressions of cause and effect. True knots may not always be present prior to delivery. Conversely, a body loop may be passed down the body of the infant by vaginal delivery, creating the false impression of a knot which was not problematic or dangerous. Nuchal loops and shoulder loops may be misinterpreted and miscounted as nuchal cords.(7) The most dramatic examples of umbilical cord complications include prolapsed umbilical cord, and rupture of the cord or a velamentous vessel. The chances of having a prolapsed cord during labour range from 1/239 cases to 2.4/1000 cases. The reported chances of fetal loss from a prolapsed cord are 8.6-49% and it appears that the ability to respond in a timely fashion may not improve outcomes.(8) The possibility of avoiding umbilical cord complications needs to be investigated.(9) In monoamniotic twins, stillbirths often occur in one twin or both because of knots and cord encirclement, a risk of 75% Many variations of umbilical cord complications exist in which factors such as the time and degree of compression are important. Fetal gestation may also play a role. Compression of the umbilical cord obstructs blood flow and oxygen and releases stress factors from endocrine organs which contribute to the immediate danger to the fetus. (10,11) On the basis of this knowledge, examination and anticipation of other cord complications is important and not difficult. Table 26.1 illustrates the current awareness of umbilical cord complications. Between 50% and 70.8% of stillbirths are unexplained.(12) It is possible that the criteria used to assess causality could be missing umbilical cord complications related to stillbirth.(13) A review of 40 unexplained stillbirths found a significant incidence of tight nuchal cords among intrapartum fetal deaths. Another study reported on perinatal deaths which may have been averted.(14) A dominant observation was failure to respond to abnormal heart-rate patterns and the authors suggested that the term fetuses were well equipped to survive until the terminal event and that such deaths could have been avoided. Back to Index Go to References Page NEXT - The Perinatal Umbilical Cord Project
Table 26.1. Estimated incidence of umbilical cord complications (UCC) and stillbirth

UCC	Incidence	Mortality

Nuchal loops	14-30%?	Unknown
Nuchal cords	14-30%	Unknown
Torsion	6-10%	20%
True knots	1%	6%
Body loops	1%	10%
Single umbilical artery	0.2%-3.6%	7%
Velamentous insertion	0.54%-2.2%	30%
Short cord	Unknown	Unknown

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