The umbilical cord (UC) delivers oxygenated blood and nutrients to the fetus in utero. As an extension of the fetal cardiovascular system, the UC blood vessels provide information about fetal cardiovascular development. However, little is known about the relationship between the structure and the biomechanical function of tissues within the UC. This thesis establishes normative data on the uniaxial tensile response of healthy UC arteries. The primary objective of this thesis is to establish data for healthy UC arteries in order to provide a benchmark for studying disease states in pregnancy.

It is well established that the maternal vasculature system during pregnancy plays an important role in the development of a healthy fetal cardiovascular system. This thesis also examines the biomechanical and morphological changes exhibited with preeclampsia (PE). PE is the most common complication during pregnancy and is characterized by the onset of hypertension and proteinuria after 32 weeks gestation. PE accounts for 76,000 maternal and 500,000 neonatal deaths annually [1, 2]. Understanding how PE affects the development of the fetus has a high potential to impact many lives by providing targets for the development of therapeutics and other bioengineering interventions. The secondary objective of this thesis is to understand how PE affects the mechanical response and function of UC arteries.

Uniaxial tensile testing was performed on UC arteries from healthy (n=11) and preeclamptic (n=4) pregnancies. Tissues exhibited a non-linear stress-strain response, which was characteristic of elastin and collagen behaving as the primary load-bearing constituents in UC arteries. Arteries were strained until the collagendependent stress-strain response was exhibited. Elastic moduli corresponding to the initial and late linear regions were determined. Results showed that the initial and late elastic moduli for healthy UC arteries was 5.03 ± 1.82 kPa and 1358 ± 388 kPa, respectively. The mode of delivery (vaginal versus Cesarean section) did not affect the mechanical response of UC arteries. Mean length of the UC did not change with PE, whereas mean UC width decreased significantly (P = 0.04) by 22.5%. Initial elastic modulus exhibited a significant increase (P = 0.003) of 86% with PE. The late elastic modulus, however, did not change significantly. Preliminary histological and scanning electron microscopy results showed that elastin content decreased and vessel walls thickened in UC arteries with PE. Overall, UC arteries exhibited a stiffer response at physiological strains.