[Transplancental exchange of oxygen in the female].

Extra-uterine survival of 20-28 weeks old fetuses is exceedingly rare. Analysis of the mechanisms of, and the conditions which permit transplacentar exchanges is fundamental for the study of the technical problems inherent in the development of an artificial placenta. Presently, extra-corporeal maintenance cannot be continued more than five days. Nevertheless, the above analyses provide directional guidelines for the pursuit of this problem.