A prospective six-year study (1975-1980) of 273 patients, monitored in the use of natural family planning (NFP), has shown that those with previously irregular menstrual cycles are disadvantaged in the subsequent use of the ovulation method after pregnancy in that they have fewer recognizable safe days and/or are more likely to have unplanned pregnancies than women who had regular cycles prior to pregnancy. Eight patients, seven nursing and one non-nursing mother, conceived during postpartum amenorrhoea. The reliability of memory in the recall of previous menstrual histories is discussed in relation to the results of an international study of menstrual cycles by the World Health Organization (WHO 1983). The relevance of prediction of menstrual events in natural family planning is also considered.
PIP: The association between former menstrual characteristics and the effectiveness of natural family planning (NFP) after pregnancy was examined in a prospective 6-year study of 273 women. There was a significant difference in menstrual cycle length between the 232 subjects who used NFP successfully and the 41 subjects who became pregnant, the cycle variance being less in patients in the former group. The study identified 2 groups of patients in relation to 24-hour total estrogen excretion during postpartum amenorrhea. Serum urinary hormone assays in the majority of patients showed uniform levels of estrogen excretion of less than 10 mcg/24 hours. However, about 1/3 of patients had erratic levels of estrogen excretion in the range of 0-35 mcg/24 hours and the mean level and variance significantly greater in this group than in the group with lower, more stable levels. The incidences of false mucus signs and of unplanned pregnancies were both significantly greater in the patients with higher, erratic levels of estrogen excretion. Moreover, a highly significant association was found between patients with erratic postpartum levels of estrogen excretion and previous irregular menstrual cycles. These findings suggest that women with a history of previous menstrual irregularities will experience problems practicing the ovulation method of NFP successfully during postpartum amenorrhea.