In many species, female body odors reflect their reproductive status, and odors around the time of ovulation attract males, resulting in behavioral and/or physiological changes. In humans, several studies have suggested that female body odor signals periods of high fertility. For instance, vaginal secretions collected during the preovulatory and ovulatory phases are rated as more pleasant than those from the menstrual, early luteal, or late luteal phases. 

Reproductive aging in women is primarily due to the gradual reduction in the number of eggs (oocytes) over time. Oocytes cannot be reproduced, and while some develop and are released during ovulation, many others diminish as they become non-viable follicles and eventually disappear. This natural decline continues until menopause, at which point fertility ends entirely. Before menopause, fertility declines mainly due to the increased presence of oocytes with abnormal chromosomes (aneuploidy), which affects their viability.

Preimplantation Genetic Testing (PGT) has been used in various forms over the last two decades. Preimplantation Genetic Testing PGT involves testing early embryos following in vitro fertilization, IVF, and has now become an accepted part of genetic testing. Nowadays, PGT serves as a resource for couples who have a family history of monogenic (single gene) disorders, wherein the fetus is at high risk of inheriting the condition.