Many types of maternal illness occurring during pregnancy have been suggested as predisposing factors leading to premature delivery of infants.1 It is entirely possible that several abnormal conditions may occur simultaneously in a patient, so that the importance of any one factor may be difficult to assess.
To help clarify this situation, our patients have been separated into groups which would more sharply indicate the influence of single factors on the incidence of prematurity. We selected for the first group mothers whose entire pregnancy, labor and delivery were, as nearly as could be determined, normal. The second group was composed of mothers who suffered one or more illnesses or abnormal conditions during pregnancy. The incidence of premature delivery among the patients of these two groups is discussed in detail in this report. The influence on prematurity rates of each of the most common abnormalities, such as syphilis, toxemia of