This study in chemical examination of the blood 1 in pregnancy was begun with the idea that, by a systematic monthly blood examination, we might be enabled to discover some finding that would give warning of impending toxemia, possibly before the onset of clinical evidence. Accordingly, a number of patients, when they presented themselves for engagement for confinement, were started on the routine examination, which was repeated monthly. In the series, we observed fifty-two patients who had normal pregnancy and normal labor. However, there were in this group a number with only one examination, because of the inaccessibility of the laboratory. The results of our observations in this group of normal cases are given in Table 1. In Chart 1, we have plotted the curves of the monthly averages of this normal group.
For the second and third months there were only six estimations, but for each of the succeeding