Selective exposure reporting and Medline indexing limited the search sensitivity for observational studies of the adverse effects of oral contraceptives

Search strategies identifying all relevant studies were possible but arguably impractical; additional research is needed to generalize our findings. Authors and editors should ensure that all interventions and outcomes examined are reported and indexers should make sure they are indexed. Central registration of observational studies and all variables they examined should be considered to assure identification of studies examining adverse events associated with health interventions.