Reliability of patient history in determining the possibility of pregnancy

In an effort to assess the reliability of patient history in excluding pregnancy, we studied the correlation between specific historical factors and the presence of a positive qualitative serum beta-human chorionic gonadotropin assay. Two hundred eight patients were studied, and information was collected prospectively on a variety of historical criteria. Three historical variables were statistically less likely to be associated with pregnancy: last menstrual period that was on time, the patient thinking she was not pregnant, and the patient stating there was no chance she could be pregnant ( P