CHRONOLOGICAL CHANGES IN PLACENTAL 

 FUNCTION 



A. St. G. Huggett 



Physiology Department, St. Mary's Hospital Medical School, 

 University of London 



Placental functions can be examined in two aspects, 

 permeability effects and endocrinal functions. The first covers 

 transmission of oxygen and nutrients from the mother and 

 of carbon dioxide and waste products from the foetus. The 

 second covers the well-recognized synthesis of reproductive 

 endocrines which affect the mother and possibly the foetus. 

 It also includes production of materials of metabolic import- 

 ance which may be demonstrable in placental cells before 

 disappearing and are to some extent the basis of Claude 

 Bernard's dictum that the placenta is the liver of the foetus. 



Unfortunately, while many different aspects of placental 

 function have been studied, there are only a limited number of 

 investigations effected at different conceptional ages and it is 

 only possible to mention a few in the time at one's disposal. 



Gellhorn and Flexner (1942) studied the passage of radio- 

 active sodium across the placenta of the rabbit and other 

 species (Fig. 1). These show increasing permeability until 

 within 10 per cent of full term but a fall off in the last 10 per 

 cent of intra-uterine life. Whether this last 10 per cent is 

 the effect of postmaturity is a point of debate, as is also the 

 standard of reference. 



Rodolfo (1934) found that the amount of antibodies passing 

 during gestation increased, but the rate of increase was 

 progressively diminished. There was no falling off. Barron 

 (1951) has investigated the oxygen passage across the placenta 

 in the sheep. There is evidence of different degrees of transfer 

 at different placental ages and increasing oxygen tension in 

 the umbilical vein blood in the last few days. 



My colleague, Dr. Wilfred Widdas, injected into pregnant 



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