The umbilical cord is a narrow narro w tube-like structure that connects the fetus (developing baby) to the placenta (afterbirth). The cord is sometimes so metimes called the baby's ³supply line´ because it carries the baby's blood back and forth, between the baby and the placenta. It delivers nutrients and oxygen to the baby and removes the baby's waste products. The umbilical cord begins to form at five weeks after conception. It becomes progressively longer until 28 weeks of pregnancy, reaching an average length of 22 to 24 inches (1). As the cord gets longer, it generally co ils around itself. The cord contains three blood vessels: vessels: two arteries and one vein.
y
The vein carries oxygen and nutrients from the placenta (which co nnects to the mother's blood supply) to the baby.
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The two arteries transport waste from the baby to the placenta (where waste is transferred to the mother's blood and disposed d isposed of by her kidneys).
A gelatin-like tissue called Wharton's jelly cushions and protects these blood vessels. A number of abnormalities can affect the umbilical cord. The cord may be too long or too short. It may connect improperly to the placenta or become knotted or compressed. Cord abnormalities can lead to problems during pregnancy or during labor and d elivery. In some cases, cord abnormali abnor malities ties are discovered d iscovered before delivery during an ultrasound. However, they usually are not discovered unt il after delivery when the cord is examined directly. The following are the most frequent cord abnormalities and their possible effects on mother and baby. What is single umbilical artery? About 1 percent of singleton and about 5 percent of multiple of multiple pregnancies (twins, triplets or more) have an umbilical cord that t hat contains only two blood vessels, instead of the no rmal three. In these cases, one artery is missing (2). The cause o f this abnormality, abnormality, called ca lled single umbilical artery, is unknown.
Studies
suggest that babies with single umbilical artery have an increased risk for birth defects,
including heart, central nervous system and urinary-tract defects and chromosomal abnormalities (2, 3). A wo man whose baby is diagnosed with single umbilical artery during a routine ultrasound may be offered o ffered certain prenatal tests to diagnose or rule out birth defects. These tests may include a detailed det ailed ultrasound, amniocentesis (to check for chromosomal abnormalities) and in some cases, echocardiography (a special type of ultrasound to evaluate the fetal heart). The provider also may recommend reco mmend that the baby have a n ultrasound after birth. What is umbilical cord prolapse? Umbilical cord prolapse occurs when the cord slips into the vagina after the membranes (bag o f waters) have ruptured, before the baby descends de scends into the birth canal. This co mplication affects about 1 in 300 births (1). The baby can put pressure on the cord as he passes through throug h the cervix and vagina during labor and delivery. Pressure on the cord reduces or cuts off blood flow from the placenta to the baby, decreasing the baby's oxygen supply. Umbilical cord prolapse can result in stillbirth unless the baby is delivered promptly, usually by cesarean section. If the woman's membranes rupture and she feels something in her vagina, she should go to the hospital immediately or, in the United States, call 911. A health care provider may suspect umbilical cord prolapse if the fetus develops heart rat e abnormalities abnormalities after the membranes have ruptured. The provider can confirm a cord prolapse by doing a pelvic examination. Cord prolapse is an emergency. Pressure on the t he cord must be relieved immediately by lifting lifting the presenting fetal part away from the cord co rd while preparing the woman for prompt cesarean delivery. The risk of umbilical cord prolapse increases if: y
The baby is in a breech (foot-first) position. position.
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The woman is in preterm labor.
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The umbilical cord is too long.
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There is too much amniotic amniot ic fluid.
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The provider ruptures the membranes to start or speed up labor.
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The woman is delivering twins vaginally. The seco nd twin is more commonly affected.
What is vasa previa? Vasa previa occurs when one or more blood vessels from the umbilical cord o r placenta cross the cervix underneath the baby. The T he blood vessels, unprotected unprot ected by the Wharton's jelly in the umbilical cord or the tissue in the placenta, p lacenta, sometimes tear when the cervix dilates o r the membranes rupture. This can result in life-threatening bleeding in the baby. Even if the blood bloo d vessels do not tear, the baby may suffer from lack of oxygen due to pressure on the blood vessels. Vasa previa occurs in 1 in 2,500 births (4). When vasa previa is diagnosed unexpectedly at delivery, more than half ha lf of affected babies are stillborn (4). However, when vasa previa is diagnosed by ultrasound earlier in pregnancy, fetal deaths generally can be prevented by delivering the baby by cesarean section at about 35 weeks of gestation (4). Pregnant women with vasa previa sometimes have painless vaginal bleeding in the second or third trimester. A pregnant woman who experiences vaginal bleeding should always report it to her health care provider so that the cause can be determined and any necessary steps taken to protect the baby. A pregnant woman may be at increased risk for vasa previa if she: y
Has a velamentous insertion of the cord co rd (the umbilical cord inserts abnormally into the fetal membranes, instead of the center o f the placenta)
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Has placenta previa (a low-lying low-lying placenta that covers part or all of the cervix) cerv ix) or certain other placental placental abnormalities
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Is expecting more than one baby
What is a nuchal cord? About 25 percent of babies are born with a nuchal cord (the umbilical cord wrapped around the baby's neck) (1). A nuchal cord, also called nuchal loops, rarely causes any problems. Babies with a nuchal cord are generally healthy. Sometimes
fetal monitoring shows heart rate abnormalities during labor and de livery in babies
with a nuchal cord. This may reflect pressure on the cord. However, the pressure is rarely serious
enough to cause death or any lasting problems, although occasionally a cesarean delivery may be needed. Less frequently, the umbilical cord becomes wrapped around other parts of the baby's body, such as a foot or hand. Genera lly, this doesn't harm the baby. What are umbilical cord knots? About 1 percent of babies are born with one or more knots in the umbilical cord (1). Some knots form during delivery when a baby with a nuchal cord is pulled through the loop. Others form during pregnancy when the baby moves around. Knots occur most often when the umbilical cord is too long and in identical-twin pregnancies. Identical twins share a single amniotic sac, and the babies' cords can become entangled. As long as the knot remains loose, it generally does not harm the baby. However, sometimes the knot or knots can be pulled tight, cutting off the baby's oxygen supply. Cord knots result in miscarriage or stillbirth in 5 percent of cases (1). During labor and delivery, a tightening knot can cause the baby to have heart rate abnormalities that are detected by fetal monitoring. In some cases, a cesarean delivery may be necessary. What is an umbilical cord cyst? Umbilical cord cysts are outpockets in the cord. They are found in about 3 percent of pregnancies (2). There are true and false cysts:
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True
ge nerally contain remnants of early embryonic cysts are lined with cells and generally
structures. y
Studies
False
cysts are fluid-filled sacs that can be re lated to a swelling of the Wharton's jelly.
suggest that both types of cysts are sometimes associated with birth defects, including
chromosomal abnormalities and kidney and abdo minal defects (2). When a cord cyst is found during an ultrasound, the provider p rovider may recommend additional tests, such as a mniocentesis mniocentesis and a detailed ultrasound, to diagnose or rule out birth defects.
Does the March of Dimes support research on o n umbilical cord abnormalities? The March of Dimes continues to support research aimed at preventing umbilical cord abnormalities and the complications they cause. One grantee is studying the development of blood vessels in the umbilical cord for insight into the causes of single umbilical artery and o ther cord abnormalities. The goals of this study are to:
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Develop a better understanding of the causes of birth defects
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Develop treatments to help prevent oxygen deprivation before and during delivery, which may contribute to cerebral palsy and other forms of brain damage da mage
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Causes of a
retained placenta
Often there is no obvious reason for the woman to retain her placenta. There are in some cases though contributing factors associated with a retained placenta, which will also determine how it is treated.
The main circumstances that can lead to a retained placenta are:
The
uterus not contracting
A f ull ull bladder 'Fiddling'
with the
uterus
A bicornuate uterus Adhesion of the placenta Emotional reactions
The
uterus not contracting. If the uterus does not contract the placenta cannot separate.
In some cases weaker, uncoordinated contractions can lead to partial separation, not being strong enough to fully detach and deliver the placenta. A strong contraction can be stimulated with either natural interventions or with oxytocic injections.
A f ull ull bladder. If the woman's bladder is full the uterus ut erus may not be able to co ntract
adequately. The placenta can stay attached or only partially separate, until the bladder is
emptied.
'Fiddling'
with the
uterus. Actions by the caregiver prodding, poking, massaging or
'rubbing up' the uterus ut erus before the placenta has separated (often referred to as 'fiddling' with the uterus) can interfere with the complete co mplete detachment of the placenta.
These procedures were commonly performed per formed in the past, aimed at stimulating stimulating a contraction. We now know t hat they can often cause weaker, irregular contractions leading to partial separation of the p lacenta and in some cases retention of o f the placenta within the uterus. Partial separation can increase t he woman's blood loss possibly leading to a postpartum haemorrhage. Prematurely pulling on the cord before the placenta separates can also cause partial part ial separation.
A bicornuate uterus. This is where the woman has an u nusually shaped uterus. A piece
of tissue or 'septum' inside the uterus (that was present before the pregnancy) extends from the top of the uterus or fundus, inside the uterus. This is also known as a 'heartshaped uterus'. The placenta may be attached over this tissue (which cannot contract), inhibiting it from separating fully from the wall of t he uterus.
Adhesion of the placenta. The placenta can adhere to t he wall of the uterus, stopping it
from separating, despite good contractions. This can be the case with women who have a history of a caesarean birth, where the placenta has adhered to scar tissue, or placenta previa where the placenta has attached low in the thin lower uterine segment.
Occasionally the placenta can attach to the muscle of the uterus, instead of the lining of the uterus. This condition is referred to as 'placenta accreta'. This is a very rare complication where the placenta is adhered to the wall of the uterus and will not separate. If the placenta is unable to be removed manually by the caregiver's hand, the doctor will try cutting it away in the operating o perating theatre.
In extremely rare circumstances a hysterectomy ma y be required or the do doctor ctor may
choose to leave the placenta, in the hope it will be naturally reabsorbed (which has varying degrees of success).
Emotional reactions. For some women the reality of parenting can be very
overwhelming and confronting as they ho ld their new child in their arms. Feelings of fear and sometimes helplessness or resentment can be issues that the individual may struggle with. If these feelings are real for the woman she can release adrenaline and shut down the release of oxytocin, stopping the contractions to expel the placenta.
Acknowledging and working with these concerns during the pregnancy can be a strategy to help deal with these emotional reactions. Asking someone to hold your baby so you can cry and release your emotions may trigger the release of the placenta and can be a way of supporting yourself at this time. Some women will use specific homoeopathic remedies or Bush Flower essences. See your practitioner during the pregnancy to have these things readily available if you need them after the birth.
References 1. Cruikshank, D.W. Breech, Other Malpresentations, Ma lpresentations, and Umbilical Cord Complications, in: Scott, J.R., et al. (eds.), Danforth's Obstetrics and Gynecology, 9th Edition. Philadelphia, Lippincott Williams and Wilkins, 2003, pages 381-395. 2. Morgan, B.L.G. and Ross, M.G. Umbilical Cord Complications. Complications. emedicine.com, March 1, 2006.
3. Gossett, D.R., et al. A ntenatal Diagnosis of Single Umbilical Artery: Is Fetal Echocardiography Warranted? Obstetrics and Gynecology, volume 100, number 5, November 2002, pages 903-908. 4. Oyelese, Y. and Smulian, J.C. Placenta Previa, Placenta Accreta, and Vasa Previa. Obstetrics and Gynecology, volume 107, number 4, April 2006, pages 927-941.
