In this short monograph the author discusses the duration of normal pregnancy, with some remarks on prematurity and postmaturity. He shows that it is impossible to predict exactly when delivery will occur, because many of the fundamental processes concerned in pregnancy are not known. Three principal questions are considered in detail: When does pregnancy begin? What causes the onset of labor? What signs warrant the physician's being certain that an infant was born at full term?
None of these questions can at present be answered completely. Many case histories are presented to illustrate instances in which pregnancy was terminated much sooner or much later than was expected from calculation by the usual methods. The medicolegal aspects of this subject are briefly mentioned. Since the factors influencing the length of pregnancy are so numerous and so little understood, the author advises caution in predicting the date of delivery.