Does the human placenta differentiate structurally during the 10th lunar month?

The placenta is the central organ of fetomaternal exchange, which metabolically provides for the growth of the fetus and its membranes as a whole. The main structural components of the human placenta develop until the beginning of the second trimester of gestation, and continue to grow and differentiate. The dynamics of the histomorphological development of the placenta lasts until birth. The aim of this stereological investigation was to analyze and compare structural components of placental parenchyma during two periods of the 10th lunar month: from the 38th to 39th week, and in the 40th week of gestation. The results show that during the last four weeks of gestation the trophoblast of the chorionic villi changes the most. At the beginning of the 10th lunar month, alpha zones, bearers of transplacental gas transport, prevail. At the end of the 10th lunar month beta zones dominate (P < 0.005). These are metabolically active parts of trophoblast. These quantitative results of stereological analysis have to be assumed as structural evidence of the physiological maturity of human placenta.