The principal work of St. Thomas Aquinas, the Summa Theologica is divided into three parts and is designed to instruct both beginners and experts in all matters of Christian Truth. It discusses topics central to Christian morality, ethics, law, and the life of Christ, providing philosophical and theological solutions to common arguments and questions surrounding the Christian faith. The views presented in this body of writing are currently upheld in large part by the modern doctrines of the Roman Catholic Church. Interesting references to and insights on ensoulment and embryology, as well as other topics discussed in Summa Theologica, indicate a strong Aristotelian and Augustinian influence.

Jacques Loeb is best known for his embryological work investigating parthenogenesis in invertebrates. Artificial Parthenogenesis and Fertilization is a revised and English-translated work from his earlier book, Die chemische Entwicklungserregung des tierischen Eies (1900). Artificial Parthenogenesis describes Loeb's many and varied methodical experiments to initiate egg development without fertilization by sperm. As is true with much of science, some of Loeb's experiments were successful and many were not. Artificial Parthenogenesis presents a sense of what early twentieth century embryology looked like: experimenters' overarching desire for manipulation and control, coupled with their use of chemicals and macromolecules as agents of change. The book also illuminates the historical role of the sea urchin in the study of embryological development.

In 2021, the World Health Organization, or WHO, published the sixth edition of their Laboratory Manual for the Examination and Processing of Human Semen, which provides standardized guidelines to physicians and other medical professionals performing semen analysis. Semen analysis is a technique that medical professionals use to analyze the characteristics of a male’s semen and sperm cells to identify possible causes of male infertility. A sperm cell is the male sex cell that fertilizes a female’s egg cell, while semen is the fluid containing sperm cells that men release during ejaculation. The WHO created the first laboratory manual for semen analysis in 1980, a time when there was no standardized way to analyze a male’s semen sample. The WHO laboratory manual was one of the first documents to standardize a procedure for evaluating human semen to look for sperm abnormalities, and it remains one of the most widespread methods of evaluating a male’s fertility potential and determining the causes of male infertility.

In December of 2016, Margus Punab and colleagues published “Causes of Male Infertility: A 9-year Prospective Monocentre Study on 1737 Patients with Reduced Total Sperm Counts,” hereafter “Male Infertility,” in the journal Human Reproduction. The study examines the main causes of severe male factor infertility, or SMF infertility, which occurs when a male’s semen has a very low number of healthy sperm cells or contains atypically low levels of sperm cells. In “Male Infertility,” the authors determine the primary cause of SMF infertility in forty percent of their participants, and among those participants, they found that the primary causes of SMF infertility were varicoceles, or enlarged veins within the loose bag of skin holding the testicles. The authors did not determine the cause of SMF infertility in the remaining sixty percent of the cases, noting a gap in the current understanding of the causes of SMF infertility. “Male Infertility” was one of the first large-scale studies to reveal certain underlying causes of SMF infertility, and its conclusions have allowed researchers to investigate fertility solutions for male patients who would otherwise not be able to reproduce.