superior and contains various bioconstituents that provide nutrition, hydration, immune factors, hormones, and other necessary components to aid infant survival and growth. Lactational strategies vary cross-culturally, but can typically be defined by sibling sets and sex ratios, frequency of nursing, entire lactational duration, and milk composition. Milk is composed of my bioconstituents, but only a few will be outlined here. In the first days of puerperium, the first milk is thick and yellowish, also called colostrum. For weeks after that, mature milk is expressed and it has been shown that fetal-mammary gland signaling occurs even before birth in determining milk type and concentrations based on the fetus sex. Colostrum plays an important role in establishing the infant gut microbiome, as it contains important immunoglobins, and is high in protein and low in fat and milk sugar such as lactose. While breastmilk is extremely important for infants' health outcomes, it is also known that human mature milk is fairly dilute, which has an effect on infant suckling behavior, which in many cases holds implications for the contraceptive properties of lactation. Lactational amenorrhea Post-partum infecundability, also referred to as lactational infecundability or lactational amenorrhea, refers to the section of the human birth interval from parturition to the first post-partum ovulation. This period varies widely across globe and between societies. The length of post-partum infecundability is heavily influenced by breastfeeding because it holds some contraceptive physiological effects. The role of lactational amenorrhea has been shown to be important for infant survival as a mechanism to delay the next pregnancy, and thus infants have a longer period to optimize nutritional and immunological benefits of breast milk. Post-partum hormonal levels change so that both estrogen and progesterone are "cleared from the maternal circulation" and without breastfeeding, levels of plasma FSH and LH gradually increase and lead to the return of regular menses within 2 months. With breastfeeding, the resumption of normal menses occurs many months later, and the overall effect of lactational amenorrhea is influenced by the intensity of infant suckling. Ovarian aging Ovarian aging is characterized by the gradual decline of the ovarian follicles number and decreasing quality of oocytes. Menopause is considered as the final stage of ovarian aging. Menopause is clinically defined as the absence of menstruation beyond a year. It indicates the cessation of reproductive phase of life in women. The biology of menopause is associated with the depletion of the