However, the placenta is a neuroendocrine organ that can synthesize and release hormones, neuroactive factors, and other mediators, allowing the proper development of the fetus’s maternal tissues to ensure an optimal pregnancy, allowing the fetus to adapt and survive under conditions of stress, infections, hypoxia, and malnutrition. It has been considered a passive organ for many years, acting as a barrier between the mother and the fetus, provide nourishing and eliminate metabolism products such as urea, uric acid, and creatinine.
This organ begins its development in days six-seven after conception. Interestingly, the neuroendocrine responses generate a feedback circuit regulated by the placenta. It also serves as a protection system against stress and immune responses. This process is regulated mainly by both the maternal brain and the placenta, acting through the maternal-placental-fetal unit (MPFU). During pregnancy, the neuroendocrine system undergoes significant hormonal fluctuations determined by stimulatory and inhibitory inputs from the mother and fetus to maintain the internal environment (milieu).