Umbilical cord

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Philippe Gloaguen
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Umbilical cord

The umbilical cord represents a important and unique link between the mother and the baby for the duration of the pregnancy. But what if it is too short or too long? Or if loops form around the baby's neck / body? What are the eventual funicular anomalies? Let's talk about.

Umbilical cord: what it is, how it is formed and how it is made

The cord, also called umbilical cord, connects the body of the fetus to the placenta, to what is called the "fetal face" of the placenta. It essentially serves to feed the baby, as it allows the passage of respiratory gases (oxygen) and nutrients from the mother to the fetus, with the return of waste elements (carbon dioxide), without there being any direct exchange between the two blood circles.

It is described as a "fetal annex", as it begins to develop from about the third / fifth week of gestation but it is present immediately, from the first moment of conception, when the blastoderm cells are formed in the embryo and are responsible for the configuration of all fetal structures. In practice, the funiculus replaces the yolk sac from a functional point of view, which guarantees nutritional supplies to the embryo in the first stages of development.

The yolk sac is initially connected to the “Chorus” (membrane that encloses the embryo and supplies it through the chorionic villi to the mother). This relationship disappears when a so-called extra-embryonic membrane develops “allantoid”, which allows breathing, nutrition and excretion of the product of conception.

It is precisely from the maturation of the allantoid that the umbilical cord develops. It is composed of a vein and two arteries coiled around it, then immersed in a gelatinous substance called “gelatina at Wharton”, soft tissue made of fibers and cellular substance which thus protects the umbilical vessels from possible trauma, and makes the cord a turgid structure, resistant to torsion, traction and compression movements.

In the two arteries it circulates venous blood which returns from the fetus to the mother to be eliminated, while circulating in the vein arterial blood that is, rich in oxygen which goes to the fetus.

At term of pregnancy it has these characteristics:

  • Length on average 57 plus or minus 15 cm
  • Diameter of about 1,5cm
  • Central, paracentral or marginal insertion on the placenta (called "racket").

Length anomalies

A funicular too long, over 70/80 cm. This excessive length could lead to the risk of forming "real knots" or even twists of the cord that can tighten the neck or other parts of the fetus body and create complications at birth, making an emergency cesarean section necessary more often than not.

An umbilical cord too short has a length of less than 30 cm. A distinction is made between an "absolute brevity" and a "relative brevity".

  • BrevitaÌ € absolute if indeed the funiculus is less than 30/20 cm. In this case, the serious possibility of the cord breaking during labor, especially during the expulsive phase, and especially in the case of hasty birth or rupture of abnormal vascular formations, must be considered.
  • Relative BrevitaÌ€ in the event that the cord has single or multiple turns around the fetus. These knots could tighten further during labor causing fetal distress.

Thickness anomalies

The funiculus could turn out too thin, with a diameter of less than 1 cm. This circumstance is associated with a fetus with conflicting (intrauterine growth retardation) and / or hypotrophic placenta. Furthermore, due to the small quantity of Warthon's jelly, the folds of the funiculus can cause occlusive episodes, with possible asphyxiation of the fetus more or less severe.

A funicular too often, with a diameter greater than 2 cm, type of "macrosome" fetuses, ie with an estimated birth weight over 4 kg.

Anomalies of vascularization

Possible anomaly is said "Single umbilical artery", where one of the two arteries is practically missing, either right or left. It often happens that the remaining artery runs into one compensatory dilatation and shows a caliber greater than 4 mm. Resistance indices (IR) also appear to be below the average for the gestational period.

This anomaly is found with an incidence of 0,5%, 1 case its 100, even if it is not a very real incidence. In fact, in fetuses with chromosomal abnormalities (type Downs), the incidence would be about 10%; in twin pregnancies the presence of the single umbilical artery (often borne by the smaller fetus) is about 3⁄4 times more frequent than in single pregnancies.

In this regard, there are two pathogenetic theories on the genesis of the single umbilical artery.

  1. La engineering theory primary (lack) of the artery.
  2. La theory of atresiaoatrophy secondary (reduction) of an artery initially present in the early stages of development.

The ultrasound examination reveals the presence of only two umbilical vessels and using the color Doppler echo, only one vessel is found lateral to the bladder, precisely the umbilical artery. This anomaly is associated with a series of fetal malformations:

  • Chromosomeopathy (trisomy 13-18 and 21)
  • Heart disease CNS abnormalities (central nervous system)
  • Genitourinary anomalies (absence of kidney)
  • Skeletal anomalies
  • Gastrointestinal anomalies
  • Abnormalities of the placenta (of form and membership)

Umbilical cord and turns around the fetus

In the case of an excessively long funiculus, this could get twisted around the fetus' neck or in other cases, to other parts of the body such as hands, arms, feet or a shoulder strap. This condition scares the expectant mother more as she thinks that the cord can "strangle" the baby and thus prevent him from breathing.

But it is important for the woman to know what it is a fairly frequent occurrence (with a frequency of 1 in 3 births) and it is often not even mentioned during childbirth, when the obstetrician or doctor draws on to untie the typical neck cord. In theory, in the case of a tight funiculus gyrus, it may rarely be necessary to clamp and sever it before disengaging the shoulders.

During labor, any cordon loop can be associated with:

  • Anomalies of the BCF (heartbeat of the fetus), often variable decelerations
  • Rarely to death of the fetus from asphyxiation. To correlate funicular turns around the neck with fetal death, the funicular sulcus must be deep and the fetus must have facial petechiae and subconjunctival hemorrhages.

In general, however, the presence of cord loops around the neck of the unborn child does not affect the possibility of carrying out the vaginal delivery, also because these loops do not cause a permanent interruption of the blood flow in the circulation, but only a compression during labor which consequently can result in a slowing down of the fetal beat.

But we know very well how during labor, especially when the mother pushes, the fetal beat slow down, precisely because the head of the unborn child is compressed by the pelvic organs, thus the intracranial pressure increases, cerebral flow is reduced and by stimulation of the vagal centers, fetal bradycardia occurs, that is, reduced heartbeat.

Therefore, the funiculus around the neck must not be associated with an adverse perinatal outcome. And just the English guidelines ACOG (American College of Obstetricians and Gynaecologist) warn that the cord around the fetus's neck should not be considered an absolute indication for the Caesarean section but we must always contextualize the event.

Prolapse of the umbilical cord and possible compression

Among the funicular pathologies that can cause serious clinical situations for the health of the fetus, we remember the "Prolapse" o "Procidenza".

We speak of prolapse of the funiculus when it is located in front of the fetal part presented with already broken amnicorial membranes; procidenza, same situation but with intact membranes. There is also talk of occult prolapse of the cord when this is located to the side of the presented part, between it and the pelvis.

There are three degrees of prolapse:

  1. Funicular in front of the presented part that does not exceed the OEU (external uterine orifice)
  2. Funicular in front of the presented part that goes beyond the OUE and goes down in the vagina
  3. Funicular in front of the part presented which is visible at the level of the vulvar rim

Several possible risk factors are highlighted that can be associated with cord prolapse. In general, these predispose to prolapse both by preventing the adaptation of the presented part to the superior strait of the pelvis and by being engaged in the birth canal.

These risk factors are divided into:

  • Maternal factors: advanced age of the woman, multiple parities, uterine malformations.
  • Fetal factors: prematurity, twin pregnancy (second twin), polyhydramnios (amount of amniotic fluid higher than normal), malformations, low birth weight.
  • Factors relating to the commitment of the submitted party: poorly presented fetus (breech or shoulder presentation), poorly positioned, high part presented, transverse or oblique situation of the fetus.
  • Factors relating to medical procedures: amnioressi (artificial rupture of the amnio chorionic membranes, especially if the fetal part is not engaged but still extrapelvic), breech version on the second twin with internal maneuvers, cephalic version with external maneuvers
Read also: The prolapse of the funiculus

In the case of a prolapsed funiculus, a possible consequence could be encountered compression of the same. This compression leads to a reduction or interruption of the blood circulation, then also accentuated by the uterine contraction.

Compression is more intense if the funiculus is between the consistent part presented (such as the head) and a hard part (such as the maternal pelvis), when fully dilated. Therefore, the compression will be less in the case of breech presentation (podium intended as butt or feet), if the fetal head is small or in the case of a high part presented, i.e. not yet engaged in the birth canal. There will be a non-existent compression in case of shoulder presentation.

The possible fetal suffering it will be proportionate to the intensity of the compression, which may be at the origin of the fetus' death from anoxia (lack of oxygen). A diagnosis of prolapsed cord is made either by observing the funiculus at the level of the vulvar introitus or by palpating it on vaginal exploration.

This exploration must always be carried out immediately after amnioressi o in case of spontaneous rupture of the membranes, especially if part presented abnormally or high, and in case of sudden and serious alteration of the fetal heartbeat (bradycardia, decelerations).

In the event that a diagnosis of a prolapsed cord is made during a vaginal examination and an abnormal BCF is also found, the midwife must maintain the exploratory fingers in the birth canal, push and keep the presented part high in order to avoid its compression on the cord and thus prevent the blood flow inside it from stopping. The woman will be placed in position Trendelemburg (head lower than the rest of the body) and immediately taken to the operating room for an emergency caesarean section.

On the other hand, in the case of funiculus procidence, therefore intact amnicorial membranes, the urgency must be activated immediately and alert the doctor, avoid further vaginal explorations as the reflex spasm could worsen the situation, stop a possible infusion of uterus tonic drugs but administration tocolytics, and if possible try to gently reposition the cord in the vagina (if in any case the fetal heartbeat is normal) in the 'waiting for the operating room to be set up.

From the moment the mortalità perinatal Depending on the interval between prolapse and childbirth, it is necessary to carry out the intervention actions very quickly, in a completely rapid and decisive way, in order to try to obtain a good chance of success.

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