ABSTRACTThe literature on the topics of quickening and auscultation of fetal heart tones as estimators of the gestational interval is reviewed. An historical overview of the use of these two events in determining the gestational interval is presented and a summary of the research on these topics is provided. Although limited, the research on each of these estimators demonstrates that the weeks of gestation at which each event occurs is highly variable among women. The use of either of these events as the only method of estimating the gestational interval is discouraged.