RESUMO
Knowledge of the factors of non-use of modern contraceptive methods should help to reduce the number of infants born after short interpregnancy intervals, which are associated with adverse effects for mothers, children, and families. For this reason, this study aimed to determine the factors associated with this non-use among mothers of infants aged 12 to 23 months. This case-control study included a sample of mothers of children aged 12 to 23 months. The case mothers were users of modern contraceptive methods and the control mothers were non-users. Data were collected from January 1 through March 31, 2018. Six factors were significantly associated with the use of modern contraceptive methods: age younger than 25 years, lack of gainful activity, desire for a family size ≥ 4 children, BMI greater than 25, opposition by husband, and failure to attend the 45-day postnatal consultation. Modifiable socio-economic factors were significantly associated with the non-use of modern contraceptive methods by mothers of children aged 12 to 23 months.