Validity and reliability of a questionnaire on fecundability.

The validity of a short questionnaire on fertility problems was tested on a group of 151 moderately educated women who had participated in a prospective study on early pregnancy failure some years before. Part of this group was approached by a personal interview, another part by telephone interviews and a third part was sent a questionnaire by mail. Reliability was tested on another population of 89 women with at least one child. The questionnaire was presented to these women twice with an interval of 3-5 weeks. The validity study showed no systematic errors for either of the approaches. Random errors were fairly large except for the personal interviews. The reliability showed great stability for the telephone interviews as well as for the mailed questionnaire. It is concluded that the questionnaire performs reasonably well, but on some items the draft questionnaire should be rephrased. The choice of a specific approach to the study population depends on the research question.