passages.id: 688
passages.type: sentence
passages.text: Sixty healthy women , half of whom had been using OCs for at least the previous 6 months , participated in the study .
entities.id: 689
entities.type: intervention
entities.text: OCs
entities.id: 690
entities.type: participant
entities.text: Sixty healthy women , half of whom had been using OCs for at least the previous 6 months ,