An experiment using a month-by-month calendar in a family planning survey in Costa Rica.

Recent demographic surveys have incorporated a month-by-month calendar for the five-year reference period before the survey for the recording of fertility-related events (sexual unions, contraceptive use, pregnancies, and breastfeeding). In the 1986 survey of Maternal and Child Health and Family Planning in Costa Rica, approximately one-half of the 3,527 women interviewed were administered a questionnaire with traditional fertility and family planning questions; the other half were asked virtually the same questions, but the women's responses were entered in a month-by-month calendar. The assignment of questionnaire type was randomly alternated by cluster. Comparisons of the number of events (live births, pregnancy losses, and contraceptive use) showed that more events were recorded among the women in the calendar group. Significantly less erroneous superposition of events (contraceptive use in the last trimester of pregnancy and hormonal contraceptive use in the first month postpartum) was noted when the calendar was used.