Classical and "true" gestational postmaturity.

In a study of a sample of 317 conceptional basal body temperature (BBT) curves obtained from normal women, the authors have applied new definitions of prematurity and postmaturity which take into account the time of ovulation. They were thus able to estimate (1) the error rates associated with the classical definitions-incorrect classification as pre- or postmature and nondetection; in particular, for this series, the percentage of incorrectly classified postmatures is high (70 per cent) and is even more so when considering only the unwanted births (80 per cent); (2) the order of magnitude in terms of days of the error made in assessing postmaturity by the classical method. This was found to be quite substantial for the misclassified cases.