The incidence of unplanned pregnancy in a cohort of 1038 mothers of nuptial children was examined. The major findings were: (1) about one third of the pregnancies were unplanned but there was little evidence that unplanned children were unwanted; (2) there was no evidence to suggest that unplanned birth was related to poor education, low socio-economic status or lack of knowledge of contraception; (3) 40 percent of unplanned births were the result of contraceptive failure; (4) a common denominator in 38 percent of unplanned births was failure or breakdown in the woman's usage of the contraceptive pill.