RESUMEN
In a randomized trial, the impact of starting day (the first and the seventh day of the period) on ovarian follicular activity was assessed during administration of a very low dose of oral contraceptive pills (20 microgram (mcg) ethinyl estradiol (EE) and 75 mcg gestodene (GS) [Meliane, Schering, Germany]). One hundred and sixty healthy women aged: 23-44 years, who had a regular cycle, and who were not using any type of oral contraceptive (OCs) steroid were studied at the Family Planning Clinic of King Chulalongkorn Memorial Hospital, Bangkok, Thailand. In the trial, each subject received a package of Meliane. They were blockwise randomized, 1:1 ratio; in the first group, subjects began their pills on the first day of their period (n = 80) and the other group, the seventh day of their period (n = 80). During the treatment cycle, ovarian activity was evaluated by transvaginal sonography (TVS) to determine the follicular-like structure (FLS). Ovulation was defined as the dominant FLS detected by TVS and followed-up every other day until its collapse. It occurred in 0 of 77 cases who started on the first day of their period and occurred in 8 of 78 cases of the group which started on the seventh day of their period. The difference was of statistical significance (p = 0.006). The result of this clinical trial is beneficial information for users of OCs containing 20 mcg EE who delay start of the OCs package.