The perinatal outcomes of asymptomatic isolated single umbilical artery in full-term neonates

Neonates with a single umbilical artery (SUA) are considered at increased risk for chromosomal and structural abnormalities, and an increased adverse perinatal outcome.

The specific aims of our study were to evaluate (1) the association of asymptomatic infants with isolated SUA and perinatal outcomes and (2) whether asymptomatic neonates with isolated SUA at birth need full investigation.

The inclusion criteria for the study were full-term neonates with isolated SUA delivered from January 1996 to December 2006. For a control group, we used the next consecutive two newborns delivered after the SUA case in the same maternity ward with matched gestational age and without phenotypic features suspicious for aneuploidy delivered after each SUA group subject. All prenatal, peripartum and delivery records were reviewed for maternal demographics, associated anomalies, karyotypic analysis, pregnancy complications and perinatal outcomes. All SUA cases had undergone sonogram for renal anomalies.

We enrolled 14 and 28 cases into the SUA and control groups respectively. There was all normal karyotyping for the 14 cases. The placental weight in SUA was significantly Lighter compared to that in the control group (597.1+/-175.4 vs. 709.3+/-95.2 g, p=0.010). All renal sonographic screens and karyotyping in the SUA group were normal. The incidence of small for gestational age (SGA) in SUA group was higher compared to control group (SGA, 5/14, 35.7% vs. 1/28, 3.6%, p=0.011) and less body length (48.7+/-5.0 vs. 50.8+/-1.8 cm, p=0.028).

SUA is a relatively rare finding. When a SUA is identified, the routine check of karyotyping and kidney sonography for possible chromosome and associated renal anomalies may be unnecessary. According to lighter placental weight probably causing the higher incidence of small for gestational age (SGA), pregnancies with isolated SUA should be carefully monitored for evidence of fetal growth restriction.