The normal umbilical cord contains 2 arteries and 1 vein (there vessel cord ) single umbilical artery is characterized by the absence of either the lep- or right umbilical artery. This malformation has a reported incidence of 0.5-6% in singleton pregnancies it increases of 3-4 times in twin pregnancies.
Single umbilical artery is of 3 types
TYPE 1– The entire length of the cord from baby to placenta , has just 2 vessels – one artery and one vein
TYPE 2– There are 3 vessel at the baby’s end of the cord but at the placental side, 2cms from the surface of the placenta, there are just 2 vessels .
The cause is anagtomosis.
Type 1 and 2 are related to problems with the umbilical cord development
TYPE 3– The cord initially has 3 vessels but occlusion close one artery of the cord .
It is related to circulatory problems in the umbilical cord and baby.
Sometimes there can be persistence of the original single allantoic artery of the baby stalk.
Prenatal ultrasound evalvation for single umbilical for single umbilical artery should be during the second and third trimester of pregnancy.
Single umbilical artery may be an isolated finding (I.E with out any other associated anomaly or chromoromal abnormality) or it may be non-isolated.
Babies with single umbilical artery are at a 6.77 times higher risk for congenital.
The most common anomalies associated with single umbilical artery are renal ( 6.48%) followed by cardio vascular (6.25%) and musculo skeletal (5.44%) .
There may be occult renal malformation like vesicoureteric reflin, grade 2 or more.
We need to maintain a low thresold for diagnosing and managing urinary tract artery infection in there babies.
Neonates with single umbilical artery have a 15 times higher risk of chromaramal abnormalities
There is a higher risk of placental abnormalities( or 3.63, 95% CI 3.01-4.39)
A higher incidence of hydramnios has also been reported in some studies ( or 2.80, 95% CI 1.42-5.49)
There is an increased risk of fetal growth restriction, prematurity, intra uterine and intra partum death among fetures with single umbilical artery .
When a 2 vessel cord is detected, a through search for other anomalies is required. A fetal 2D-ECHO is warranted.
Invasive testing is not recommended in isolated single umbilical artery.
Invasive testing with chromoromal evalvation (Micro array) is recommended if associated malformations are detected. Studies have shown a higher incidence of amniocentesis in there patients ( or 2.52, 95%, CI 1.82-3.15).
Serial growth scans with doppler indices are needed once a 2 vessel cord is seen
For normal weight fetures with isolated single umbilical artery and normal insertion of the cord, no particular precautions during labour are needed and induction can be performed
Studies have shown a higher incidence of cesarean section in these women ( due to prematurity, fetal growth restriction and oligohydramnios ) .
Neonates night have a prolonged NICU stay.
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- Chow J S etal, frequency and nature of structural anomalies in fetuses with single umbilical artery, J ultrasound Med 1998; 17; 765-8
- Murphy-kaulbeck etal. Single umbilical artery risk factors and pregnanacy outcomes. Obstet Gynac 2010, 116; 843-50.
- Single umbilical artery- risk factors and pregnancy outcomes. Obstetrics and gynaecology 116(4) ;843-50.