Embryo transfer (ET) has transformed swine biotechnology, enabling genetic advancements and disease control. However, its success remains inconsistent, partly due to immune-mediated challenges at the maternal-fetal interface. This study explores the immunological environment of hemi-allogeneic pregnancies (via artificial insemination, AI) versus allogeneic pregnancies (via ET) in pigs during the critical implantation phase. Sows were categorized into groups based on pregnancy type and fetal counts, reflecting varying outcomes. Endometrial immune cell populations, including T lymphocytes, regulatory T cells (T