Routine reporting registers can be used to indicate if HIV-infected women report the use of a modern family planning method. This question can also be included in population-based surveys, such as an AIDS Indicator Survey, or adaptations to Fertility and Family Surveys (FFS), Reproductive Health Surveys (RHS) and other surveys based on similar methodologies. The time frame used to assess contraceptive prevalence can also vary. In most surveys there is no definition of what is meant by “currently using” a method of contraception. In some surveys, the lack of probing questions, asked to ensure that the respondent understands the meaning of the different contraceptive methods, can result in an underestimation of contraceptive prevalence, in particular for non-traditional methods. Sampling variability can also be an issue, especially when contraceptive prevalence is measured for a specific subgroup (according to method, age-group, level of educational attainment, place of residence, etc) or when analyzing trends over time. Regional and global estimates of contraceptive prevalence rates are based on weighted averages, using the total number of women of reproductive age (15-49) who are married or in union. These estimates are presented only if available data cover at least 50% of total number of women of reproductive age (15-49) who are married or in union in the regional or global groupings.