The present paper describes the relationship between the use of oral contraceptives and arterial blood pressure among women residing in rural, urban and metropolitan areas of Rio Grande do Sul, the southernmost state of Brazil. The analysis is based on data from a cross-sectional survey of blood pressure carried out in Rio Grande do Sul, in 1978. In an analysis ofcovariance, controlling forage and Quetelet Index, the average systolic and diastolic pressures of oral contraceptive users or ex-users were compared to the average pressure of never-users. A positive difference in systolic pressure was observed systematically for all four study strata (Rural Interior, Urban Interior, Capital and its Metropolitan Belt), among women using oral contraceptives at the time of interview. The difference was found to be significant (p < 1%) for women residing in the Metropolitan Belt using oral contraceptives for more than 2 y ears. The effect on diastolic pressure, although generally positive, were smaller and not significant. The research methodology allowed for the association between the use of oral contraceptives and other risk factors to be evaluated. The effect on blood pressure was found to be most intense for women of the lowest educational status residing in the Metropolitan belt. For the group of women with a history of hypertension during pregnancy or classified as hypertensive (criteria 140/90) the effect of oral contraceptives was also found to be highly significant (p <1%) - an alteration of over IQmmHg on the average systolic pressure. These results suggest that the use of oral contraceptives brings about a greater increase in systolic pressure in groups of women with normally higher levels of pressure.
