The Mechanical Environment of Pregnancy: Characterizing the Material Remodeling of Primate Reproductive Tissues

All human lives start with pregnancy. A pathological pregnancy can be physically, mentally, and financially detrimental to newborns and families. Preterm labor and birth (PTB) is one of the most serious pathological conditions associated with pregnancy. PTB affects 10% of global births and is the leading cause of death in children under five years of age. Multiple etiologies are identified for causing PTB and three major reproductive tissues are involved: the uterus, the cervix, and the feto–maternal interface. Throughout pregnancy, these reproductive tissues change in response to various signals, a process called remodeling. Timely and appropriate remodeling of these tissues is needed for a healthy pregnancy. One central element of remodeling is a change in tissues’ mechanical properties, the focus of this work. This dissertation investigates the mechanical environment of pregnancy by characterizing the remodeling of three reproductive tissues of primates (humans and Rhesus macaque monkeys) and computationally simulating pregnancy physiology. I combine comprehensive mechanical testing with digital image correlation (DIC) to capture the material behavior of reproductive tissues, characterize the architecture of these tissues’ fiber networks by optical coherence tomography (OCT), implement a microstructurally-inspired constitutive mate- rial model, conduct inverse finite element analysis (IFEA) to quantify observed remodeling, and finally use finite element analysis (FEA) to simulate pregnancy anatomy and physiology. Results presented here demonstrate that the non-human primate (NHP) cervix, human uterus, and NHP feto–maternal interface all undergo remodeling during pregnancy and experience com- plex stress conditions. In general, the NHP cervix becomes softer and more extensible, with distinct stages. While the ground substance compressibility stays approximately the same throughout gestation, the fiber network steadily becomes more extensible, though rapidly becomes less stiff and more dispersed during the ...