ENROLLMENT INTO BIRTH-TO-10 (BTT) - POPULATION AND SAMPLE CHARACTERISTICS

The population under study in the South African longitudinal study of urban children and their families, 'Birth to Ten' (BTT), comprised all births during a 7-week period from April to June 1990 in Soweto-Johan nesburg. Specification of the population base for the cohort was hampe red by a number of flaws in the notification and record-keeping system s of the local authorities. As far as could be ascertained, 5460 singl eton births occurred during this time to women who gave a permanent ad dress within the defined region. Enrolment into BTT took place over th e first 15 months of the study and covered the antenatal, delivery, 6- month and 1-year periods. By the end of this time, and despite a major health service strike during the delivery phase, 74% of all births (4 029 cases) had been enrolled into the study. There were marked variati ons in levels of enrolment, however, by population group membership, r esidential area and place of delivery. In general, there was substanti al under-enrolment of largely middle-class white women and their babie s. Initial non-enrolment of specific segments of the population and at trition of the enrolled sample up to the end of the first year are dis cussed in the context of racial and social differentiation in South Af rica.