The nutrition of the human fetus is a difficult subject to study on account of the almost complete isolation of this body. The physiologic activities of mother and offspring, as well as the röle the placenta has played in the development of the latter, must be represented to a certain degree by the products of metabolism circulating in the blood streams of both organisms. By comparison of the amounts of nutriments and waste substances simultaneously present in the blood of each of the two subjects some information ought to be obtained concerning the "parasitic existence" of the fetus. Slemons1 in particular has contributed some data to the question. However, the need for more positive evidence has led us to extend this type of work.
Do the derivatives of the protein and fat in the maternal intake reach the fetus in the form of "building stones" (such as amino-acids, etc.)
HOWE MG, GIVENS MH. CHEMICAL STUDIES OF THE BLOOD OF MOTHER AND FETUS. Am J Dis Child. 1923;25(1):63-75. doi:10.1001/archpedi.1923.01920010068005