Fetal Isolated Single Umbilical Artery (ISUA) and Its Role as a Marker of Adverse Perinatal Outcomes

Single umbilical artery (SUA) is considered an ultrasound marker of anomalies. Although it may be present in about 0.5% to 6% of normal pregnancies, it has been linked with an increased risk of fetal growth restriction (FGR), as well as cardiac, genitourinary and gastrointestinal malformations and chromosomal anomalies such as trisomies 21 and 18. Objectives: This study aims to evaluate whether the presence of isolated SUA (ISUA) is associated with adverse perinatal outcomes. Methods: A descriptive, observational and retrospective study was conducted, analyzing 1234 pregnancies (1157 normal gestations with a three-vessel cord and 77 cases of ISUA). Results: ISUA was associated with a lower gestational age (38 vs. 39 weeks) and a lower birth weight (3013 vs. 3183 g) when performing a univariate analysis. However, after performing a multivariate analysis adjusted for maternal age and BMI, the association between single umbilical artery (SUA) and lower birth weight could not be proven. No significant differences were found in the rate of malformations, genetic disorders, Apgar score, pH at birth or admissions in the neonatal ICU. Conclusions: ISUA is associated with a lower birth weight but does not increase the risk of prematurity or low-birth-weight-related neonatal admissions. Additionally, ISUA is not significantly associated with a lower gestational age, genetic disorders, fetal malformations, worse Apgar scores or lower pH values at birth.