Abstract
The role of the maternal-fetoplacental hormonal system in the maintenance of pregnancy and in the onset of labor was studied by meaiuring the serum progesterone level in the maternal vein, the umbilical vein and artery at term (n = 34) and in the case of premature births (n = 74). Our results show: 1) During the 28th–40th weeks the serum progesterone concentration in the umbilical vein is greater than in the maternal vein (p >0.01) and in the umbilical artery (p >0.01), and greater in the umbilical artery then in the maternal vein (p>0.01). 2) No correlation was found between the serum progesterone concentration in the maternal and fetal vessels, whereas a close correlation was found between the serum concentration in the umbilical vein and artery. 3) The progesterone concentration of the maternal serum increased during the 28th–40th weeks, but increased only during 28th–36th week in the umbilical vein and artery and fell significant by the 40th week. From this it appears that the maternal and the fetal progesterone concentrations are interdependent. The progesterone concentration of the umbilical vessels falls before term but it is not an essential factor in the onset of labor.