The effect of multivitamin supplements on continuation rate and side effects of combined oral contraceptives: A randomised controlled trial.

Objectives: This study aimed to assess the effect of multivitamin use during the pill-free interval on the continuation rate and side effects of combined oral contraceptives (COCs) within the first few cycles of use.

Methods: In this trial, 332 women presenting to public health centres in an Iranian city each received a COC pack containing 21 pills and were randomised to one of three groups: two of the groups also received 42 multivitamin pills or 42 placebo pills to be taken once a day for 7 days before starting COCs and again during the 7-day pill-free interval for five cycles, while the third group received no multivitamin or placebo pills with their COCs. The groups were compared using Cox regression and χ(2) tests.