| Umbilical cord |
|
|
| A newborn's sinew-like cord stump, after "Delayed Severance" without cord clamping, known as an Early
Lotus Birth |
|
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| Newborn still attached to its unclamped, pulsing cord, just before the birth of the placenta,
homebirth. |
| Latin |
funiculus umbilicalis, chorda umbilicalis |
| Days |
29 |
| Dorlands/Elsevier |
c_55/12259050 |
In placental mammals, the umbilical cord is a tube that connects a developing
embryo or fetus to the placenta.
It normally contains three vessels, two arteries (Umbilical artery) and one vein (Umbilical vein), buried within
Wharton's jelly, for the exchange of nutrient- and
oxygen-rich blood between the embryo and placenta. The presence of only two vessels in the cord is sometimes related to abnormalities in the fetus, but
may occur without accompanying abnormalities.
Shortly after birth, upon exposure to temperature change, the gelatinous Wharton's Jelly substance undergoes a physiological
change that collapses previous structure boundaries and in effect creates a natural clamp on the umbilical cord which halts
placental blood return to the neonate, causing the cord to cease pulsation. Though generally occurring as soon as 5 minutes after
human birth, if the neonate's cord is submerged in warm water (i.e., a birthing pool) the cord may continue pulsing an additional
time, up to 15-20 minutes. General obstetric practice introduces artificial clamping as early as 1 minute after birth of the
neonate, a routine protocol questioned by some parents and care providers.
Explanation
The umbilical cord develops from the same sperm and egg from which the placenta and fetus develop, and contains remnants of
the yolk sac and allantois. In humans, the umbilical cord in
a full term neonate is usually about 50 centimetres (19.7
in) long and about 2 centimetres (0.75 in) diameter, shrinking rapidly in diameter in the
after birth.
In the third stage of labour, after the child is born, the uterus spontaneously expels the
neonate's placenta along with the cord from the mother's body, 10–45 minutes after the birth. However, the umbilical cord is
generally clamped during or within minutes of birth and severed shortly after, a practice of "active management of labor" which
has become increasingly controversial due to the lower transfer of placental blood to the neonate and associated stressors.
The health benefits of non-clamping of the cord and delayed umbilical severance are receiving attention in medical
journals.[1][2][3]
Today there are umbilical cord clamps which combine the cord clamps with the knife. These clamps are safer and faster,
allowing one to first apply the cord clamp and then cut the umbilical cord. After the cord is clamped and cut (Western
obstetrical protocol) the newborn wears a plastic clip on the navel area until the compressed
region of the cord has dried and sealed sufficiently. The remaining umbilical stub remains for up to 2–3 weeks as it dries and
then falls off. In nonseverance scenarios, also called lotus birth, the umbilical cord is
wrapped up to within an inch of the newborn's belly, and the entire intact cord is allowed to dry like a sinew, which then falls
off.[4]
Makeup and composition
The umbilical cord is made of Wharton's jelly, not ordinary skin and connective tissue. There are no nerves, so cutting it is
not painful, but it is very strong, like thick sinew, and requires a sharp instrument if it is to be cut. Provided that umbilical
severance occurs after the cord has stopped pulsing (5-20 minutes after birth), there is ordinarily no significant loss of either
infant or maternal blood while cutting the cord. The cord contains two arteries which carry deoxygenated blood (from the fetus
back to the mother) and one vein that carries oxygenated blood (from the mother to the fetus).
Historical commentary
“Another thing very injurious to the child, is the tying and cutting of the navel string too soon; which should always be left
till the child has not only repeatedly breathed but till all pulsation in the cord ceases. As otherwise the child is much weaker
than it ought to be, a portion of the blood being left in the placenta, which ought to have been in the child.”
Erasmus Darwin, Zoonomia, 1801
Cord blood
A newborn at 45 seconds, with
umbilical cord clamped and umbilical blood unable to return to fetal circulation, showing
signs of distress.
Provided that the cord is not clamped for the first 5 minutes after birth, and kept level with the newborn, it pulses red
blood cells into the neonatal circulatory system, providing the neonate with one-third to one-half of its entire blood volume.
This cord blood is a rich source of primitive, undifferentiated
stem cells (i.e. CD34-positive and CD38-negative) which assist in neonatal adaptation.
A cord blood bank is in the business of cord blood harvesting, and is NASDAQ listed.
These companies promote very early cord clamping and cutting, to freeze for long-term cryo-storage at a cord blood bank should the child ever require the cord blood stem cells for rare diseases (for example,
to replace bone marrow destroyed when treating leukemia).
This practice is controversial: the RCOG (Royal College of Obstetricians and Gynaecologists, Great Britain) in its 2006 opinion
states, "There is still insufficient evidence to recommend directed commercial cord blood collection and stem-cell storage in
low-risk families." Child health advocates criticize the aggressive marketing campaigns of blood banks to pregnant parents-to-be
as misleading, and assert that early cord blood withdrawal may actually increase the likelihood of childhood disease.
For-profit cord blood banks receive from 80 ml to 180 ml of blood on the average amount of blood taken for CBC (cord blood
collection). 'Banking' cord blood involves immediate, very early cord clamping to take a significant amount of blood (100mL on
average) from the newborn at a crucial neonatal time. The amount of blood taken from the newborn child by early cord clamping can
be understood by the fact that a 9 pound baby only creates 10 ounces of blood (300 ml). Therefore 180 ml is actually more than
half this baby's blood supply and taking half of one's blood supply will weaken any child, or any adult that loses blood.
The cord banking business markets the use of CBEs as a mechanism that would eliminate the ethical difficulties associated with
embryonic stem cells, however cord blood harvesting itself is fraught with ethical
difficulties. (ESCs).[5]
The American Academy of Pediatrics 2007 Policy Statement on Cord Blood Banking title
states that:
"Physicians should be aware of the unsubstantiated claims of private cord blood banks made to future parents that promise to
insure infants or family members against serious illnesses in the future by use of the stem cells contained in cord blood;"
"Cord blood collection should not be performed in complicated deliveries. The cord blood stem cell–collection program should
not alter routine practice for the timing of umbilical cord clamping;" and
"Private storage of cord blood as "biological insurance" should be discouraged, and that cord blood banks should comply with
national accreditation standards developed by the Foundation for the Accreditation of Cellular Therapy (FACT), the US Food and
Drug Administration (FDA), the Federal Trade Commission, and similar state agencies."
Problems
A number of abnormalities can affect the umbilical cord, which can cause problems that affect both mother and child:
Animals
In other mammals, the mother animal generally will gnaw the cord off separating the placenta from the baby. It is often
consumed by the mother which nourishes her, and reduces tissue that would attract scavengers or predators. In chimpanzees, the mother focuses no attention on umbilical severance, instead staying still and nursing and
holding her baby (with cord, placenta, and all) until the cord dries and separates within a day of birth, at which time she
leaves the cord and placenta on the forest floor where it is recycled by scavengers. This was first documented by zoologists in
the wild in 1974.[citation needed]
Other uses for the term "umbilical cord"
The term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as the
hose connecting a surface-supplied diver to his surface supply of air and/or
heating, or a space-suited astronaut to his
spacecraft.
The phrase "cutting the umbilical cord" is used symbolically to describe a child's breaking away from the parental home.
Additional images
Diagram illustrating a later stage in the development of the umbilical cord.
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Fetus of about eight weeks, enclosed in the amnion. Magnified a little over two diameters.
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Sectional plan of the gravid uterus in the third and fourth month.
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Fetus in utero, between fifth and sixth months.
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Scheme of placental circulation.
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Human embryo with heart and anterior body-wall removed to show the sinus venosus and its tributaries.
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References
External Links
- Full Policy Statement of the American Academy of Pediatrics on Cord Blood: [[1]]
- Three frequently asked questions of your Newborn Umbilical Cord: [[2]]
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