Trends in female circumcision between 1933 and 2003 in Osun and Ogun States, Nigeria (a cohort analysis).

The international movement against female circumcision gained momentum in the past two decades. Although recent studies report decline in the practice none has studied the cohort effect or provided plausible explanation for such decline. Changes in female circumcision occurring in two southwestern States of Nigeria between 1933 and 2003 were tracked in a cross-sectional survey using cohort analysis. 1174 female live births to 413 women were included in the analysis. About fifty-three percent of all females were circumcised. The prevalence dropped from 64.9% during the period 1933-60 to 25.7% for the period 2000-2003. For first order births, the corresponding rates were 58.8% and 25.0%. The decline for first-born females comes a decade before other birth orders. Age and education of mother are two main factors of the decline. Global consensus or legal enforcement plays secondary roles. Understanding how modernisation affects the decline in female circumcision should receive greater attention.