Data from antenatal clinics in Botswana provide information on age, HIV status, and geographic cluster (clinic) for women in their child-bearing years. To make use of these data, it is necessary to extend spline estimation methods to adjust for correlation that arises due to geographic proximity of clinics and closeness in age among women within clinics. We use a logistic model with mean function specified by natural cubic splines, and a composite likelihood approach to accommodate all possible pairs of geographical clusters. These methods allow us to generate smooth estimates of age-specific HIV prevalence in Botswana. Repeated measures of such estimates will ultimately be useful in evaluating the impact of HIV prevention strategies on HIV incidence in women of child-bearing age.