Children born with congenital heart defects typically undergo staged palliative surgeries to reconstruct the circulation to improve transport of deoxygenated blood to the lungs. As part of the first surgery, a temporary shunt (Blalock-Thomas-Taussig) is often created in neonates to connect a systemic and a pulmonary artery. Standard-of-care shunts are synthetic, which can lead to thrombosis, and much stiffer than the two host vessels, which can cause adverse mechanobiological responses. Moreover, the neonatal vasculature can undergo significant changes in size and structure over a short period, thus constraining the use of a non-growing synthetic shunt. Recent studies suggest that autologous umbilical vessels could serve as improved shunts, but there has not been a detailed biomechanical characterization of the four primary vessels – subclavian artery, pulmonary artery, umbilical vein, and umbilical artery. Herein, we biomechanically phenotype umbilical veins and arteries from prenatal mice (E18.5) and compare them to subclavian and pulmonary arteries harvested at two critical postnatal developmental ages (P10, P21). Comparisons include age-specific physiological conditions and simulated ‘surgical-like’ shunt conditions. Results suggest that the intact umbilical vein is a better choice as a shunt than the umbilical artery due to concerns with lumen closure and constriction related intramural damage in the latter. Yet, decellularization of umbilical arteries may be a viable alternative, with the possibility of host cellular infiltration and subsequent remodeling. Given recent efforts using autologous umbilical vessels as Blalock-Thomas-Taussig shunts in a clinical trial, our findings highlight aspects of the associated biomechanics that deserve further investigation.