The Relationship of the Size and Composition of the Human Placenta to Its Functional Capacity

Summary An analysis was made of placentae from 500 consecutive deliveries of live singleton babies in the Royal Free Hospital, and of a further series of “high risk” patients, so as to bring the combined series to 700 cases. The mother's age, height, parity, duration and complications of pregnancy, the type of delivery, the sex, birthweight and Apgar score of the child, and the weight and composition of the placenta were recorded and correlated. Premature deliveries were significantly more common among short mothers, and with male children. Low Apgar scores were more common among babies born before 34 weeks gestation, but after that time there was no apparent relationship between duration of gestation and Apgar score. The gross weight of the trimmed placenta continued to increase with advancing pregnancy duration, but this was entirely due to increased blood trapping in postmature placentae; the weight of the blood‐free placenta did not increase after term. The blood‐free weight of the placenta of dysmature babies bore approximately the same relationship to the weight of the baby as did that of well‐grown babies, but the dysmature placenta contained a greater proportion of insoluble, and presumably metabolically inert, protein. It is concluded that to assess functional placental size it is necessary to correct for the amount of blood trapped in the placenta after drainage. However, the assessment of protein solubility is tedious and makes only a minor contribution to the estimation of the functional capacity of the placenta.