Abstract
One in four people attempting to conceive will experience infertility. The current theory is that infertility is caused by a decreased number and quality of eggs in the ovary. However, ovarian aging cannot be the sole cause of infertility. In natural conception, the first days of embryonic growth occur within the oviduct. In IVF, this growth period occurs in the lab, eliminating the oviduct's effect on the embryo. Previously the role of the oviduct has not been questioned. The difference of embryos reaching the blastocyst stage between young and aged mice was quantified to establish the extent of the preimplantation loss. To investigate the level of expression of growth promoters and inhibitors in the oviducts of aged and young mice during pregnancy, RT-qPCR was completed. Additionally, spectral cytometry was used to investigate if a change in the Treg cell population occurred with advancing maternal age. This study showed that the number of embryos surviving to the blastocyst stage was significantly decreased in aged mice. No difference was identified between young and aged mice and the expression of embryo growth-promoting or inhibiting factors within the oviduct. This study concluded that there were no changes in the presence of T regulatory cells with advancing maternal age. Our results showed that preimplantation loss is increased in aged mice compared to young mice due to a post-ovulatory effect. We confirmed that the increase in preimplantation loss is not due to a change in the expression of growth promoters or inhibitors within the oviduct. Nor is it due to a change in the response of the maternal inflammatory system to pregnancy. We postulate that an increase in abnormal eggs within the ovary is occurring with advancing maternal age, and is resulting in an increased number of aneuploidy embryos degrading before implantation.