Single Umbilical Artery and Its Associated Findings

Abstract

Single umbilical artery (SUA) is diagnosed in about 1% of live-born fetuses. Although there is no consensus on the clinical relevance of this diagnosis, a number of studies have reported associations between SUA and adverse fetal outcomes, such as intrauterine growth restriction (IUGR), prematurity, and congenital renal anomalies. However, these findings have been refuted by other studies that found no increased risk of IUGR or congenital malformations associated with SUA. Many of these negative studies have limited value because of small sample size, incomplete follow-up, and lack of adjustment for possible confounding factors (especially demographic differences between the comparison populations). This retrospective cohort study investigated the association between a finding of SUA and the occurrence of IUGR, fetal death, renal and cardiac anomalies, and other adverse pregnancy outcomes. The cohort was comprised of all consecutive patients with singleton pregnancies, undergoing a routine sonographic anatomic survey between 1990 and 2007 at a major tertiary medical center. Demographic information on history and pregnancy outcomes was entered into a prenatal database. The incidence of adverse pregnancy outcomes in pregnancies with SUA and those with 2 umbilical arteries (dual umbilical arteries [DUA]) was compared. The primary study outcomes were IUGR (less than the 10th percentile for gestational age), and renal and cardiac anomalies. Multivariable logistic regression was used to assess the association between SUA and defined outcomes and to adjust for potentially confounding variables. Of the 64,047 pregnancies available for follow-up analysis, 392 were cases of SUA (0.61%) and 63,655 were cases of DUA. After excluding all fetuses with known anomalies and adjusting for gestational diabetes, smoking, African-American race, and preeclampsia, pregnancies with SUA were associated with a greater than 2-fold increased risk in IUGR compared to those with DUA (adjusted odds ratio [aOR], 2.1; 95% confidence interval [CI], 1.6-2.7; P < 0.01). After adjusting for pregestational diabetes, SUA was associated with a more than 20-fold increased risk of cardiac anomalies compared to cases with DUA (aOR, 20.3; 95% CI, 13.6-30.5; P < 0.01) and after adjusting for fetal male sex and advanced maternal age, it was associated with a nearly 3-fold increased risk of renal anomalies (aOR, 3.0; 95% CI, 1.9-4.9; P < 0.01). These findings indicate a significant increase in the incidence of IUGR and renal and cardiac anomalies in pregnancies with SUA compared to those with DUA. These data suggest that it would be reasonable to perform ultrasound screening for IUGR and structural anomalies in pregnancies complicated by SUA.