The EuroSIDA study recruits HIV-1 positive patients above the age of 16 years in the proportions in which they are represented in the participating clinics, which ensures that women are proportionally represented in the study. Approximately 26% of the patients are women. The study does not intervene with the clinical management of the patients followed, but only collects information based on provider-patient interviews, from patient records and from plasma samples collected. Pregnant women may participate in the study, as no interference with their treatment or pregnancy in any way will take place. Data on frequency and outcome of pregnancy are collected in the study once a year.