ABSTRACT
A randomized double blind clinical trial was carried out at the Division of Family Planning, Siriraj Hospital in order to study the efficiency of low dose oral contraceptive pills, containing 0.03 mg ethinyl estradiol and 0.15 mg levonorgestel, for postponement of menstruation. Sixty hralthy women with previous regular menstruation were randomly assigned to one of two study groups. Thirty women in the control group received 10 capsules of a placebo and the other 30 women in the study group received 10 capsules that contained the oral contraceptives. The women in both groups began taking the in doses of one capsule per day for three days before the expected date of menstruation. The characteristics of both groups were comparable. The number of women who expected postponement of their menstruation were recorded together with the side-effects. The results showed that oral contraceptive pills taken three days before the expected date of menstruation could postpone menstruation significantly (27/30 vs 2/30, p< 0.05). The major side-effects were headache (10 percent) and nausea (13.3 percent).