Single umbilical artery
Encyclopedia
Occasionally, there is only the one single umbilical artery (SUA) present in the umbilical cord
. Approximately this affects between 1 in 100 and 1 in 500 pregnancies, making it the most common umbilical abnormality. It is more common in multiple births. Its cause is not known.
Most cords have one vein and two arteries. The vein carries oxygenated blood from the placenta to the baby and the arteries carry deoxygenated blood from the baby to the placenta. In approximately 1% of pregnancies there are only two vessels —usually a single vein and single artery. In about 75% of those cases, the baby is entirely normal and healthy and the missing artery isn't missed at all. One artery can support a pregnancy and does not necessarily indicate problems. For the other 25%, a 2-vessel cord is a sign that the baby has other abnormalities—sometimes life threatening and sometimes not. SUA does increase the risk of the baby having heart, skeletal, intestinal or kidney problems. Babies with SUA may have a higher likelihood of having other congenital abnormalities, especially of the heart. However, additional testing (high level ultrasound scans) can rule out many of these abnormalities prior to birth and alleviate parental anxiety. Echocardiograms of the fetus may be advised to ensure the heart is functioning properly. Genetic counseling may be useful, too, especially when weighing the pros and cons of more invasive procedures such as chorionic villus sampling
and amniocentesis
.
Although the presence of an SUA is a risk factor for additional complications, most fetuses with the condition will not experience other problems, either in utero or after birth. Especially encouraging are cases in which no other soft markers for congenital abnormalities are visible via ultrasound. Prior to ultrasound technology, the only method for determining the presence of a SUA was at birth, following an examination of the placenta. Given that the vast majority of expectant mothers do not receive the kind of advanced ultrasound scanning required to confirm SUA in utero, most cases may never be detected antenatally even today.
Doctors and midwives often suggest parents take the added precaution of having regular growth scans near term to rule out intrauterine growth restriction, which can happen on occasion and warrant intervention. Yet the majority of growth restricted infants with the abnormality also have other defects. Finally, neonates with the finding may also have a higher occurrence of kidney problems, so close examination of the infant may be warranted shortly after birth. Among SUA infants, there is a slightly elevated risk for post-natal urinary infections.
It may be associated with Patau syndrome
.
Umbilical cord
In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
. Approximately this affects between 1 in 100 and 1 in 500 pregnancies, making it the most common umbilical abnormality. It is more common in multiple births. Its cause is not known.
Most cords have one vein and two arteries. The vein carries oxygenated blood from the placenta to the baby and the arteries carry deoxygenated blood from the baby to the placenta. In approximately 1% of pregnancies there are only two vessels —usually a single vein and single artery. In about 75% of those cases, the baby is entirely normal and healthy and the missing artery isn't missed at all. One artery can support a pregnancy and does not necessarily indicate problems. For the other 25%, a 2-vessel cord is a sign that the baby has other abnormalities—sometimes life threatening and sometimes not. SUA does increase the risk of the baby having heart, skeletal, intestinal or kidney problems. Babies with SUA may have a higher likelihood of having other congenital abnormalities, especially of the heart. However, additional testing (high level ultrasound scans) can rule out many of these abnormalities prior to birth and alleviate parental anxiety. Echocardiograms of the fetus may be advised to ensure the heart is functioning properly. Genetic counseling may be useful, too, especially when weighing the pros and cons of more invasive procedures such as chorionic villus sampling
Chorionic villus sampling
Chorionic villus sampling , sometimes misspelled "chorionic villous sampling", is a form of prenatal diagnosis to determine chromosomal or genetic disorders in the fetus. It entails sampling of the chorionic villus and testing it...
and amniocentesis
Amniocentesis
Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for...
.
Although the presence of an SUA is a risk factor for additional complications, most fetuses with the condition will not experience other problems, either in utero or after birth. Especially encouraging are cases in which no other soft markers for congenital abnormalities are visible via ultrasound. Prior to ultrasound technology, the only method for determining the presence of a SUA was at birth, following an examination of the placenta. Given that the vast majority of expectant mothers do not receive the kind of advanced ultrasound scanning required to confirm SUA in utero, most cases may never be detected antenatally even today.
Doctors and midwives often suggest parents take the added precaution of having regular growth scans near term to rule out intrauterine growth restriction, which can happen on occasion and warrant intervention. Yet the majority of growth restricted infants with the abnormality also have other defects. Finally, neonates with the finding may also have a higher occurrence of kidney problems, so close examination of the infant may be warranted shortly after birth. Among SUA infants, there is a slightly elevated risk for post-natal urinary infections.
It may be associated with Patau syndrome
Patau syndrome
Patau syndrome, also known as trisomy 13 and trisomy D, is a chromosomal abnormality, a syndrome in which a patient has an additional chromosome 13 due to a nondisjunction of chromosomes during meiosis. Some are caused by Robertsonian translocations...
.