Ovulation incidence with oral contraceptives: a literature review.

BACKGROUND AND METHODOLOGY Combined oral contraceptives (COCs) provide reliable and convenient contraception, although contraindications and tolerability issues may limit their use in some women. Progestogen-only pills (POPs) may be more suitable for some women, however, traditional POPs do not have the same contraceptive efficacy as COCs. A literature search was performed in order to assess the incidence of ovulation with available COCs, traditional POPs and with a desogestrel POP [Cerazette, 75 microg desogestrel (DSG)]. The following databases were searched: MEDLINE, EMBASE, Biosis, Derwent Drug File, Current Contents and the in-house Organon database 'Docs' (which contains all published reports of Organon products). Searches used free-text terms [e.g. Contraceptive$ in combination with (Ovulat$ adj Rate$), (Ovar$ adj Activ$) or (Escap$ adj Ovulat$)] and were limited to the search criteria 'Human' and 'from 1979 onwards'. The searches included publications up to July 2008. RESULTS Many of the studies were hampered by inadequate ovulation criteria; however, the overall incidence of ovulation determined by the reports uncovered in the literature search was 2.0% [95% confidence interval (CI) 1.1-3.3] with COCs containing 30-35 microg ethinylestradiol (EE), 1.1% (95% CI 0.60-2.0) with 15-20 microg EE COCs, 4.6% (95% CI 2.8-6.9) with phasic COCs, 1.25% (95% CI 0.03-6.8) with Cerazette and 42.6% (95% CI 33.4-52.2) with traditional POPs. CONCLUSIONS The findings indicate that COCs and the desogestrel POP are equally effective in suppressing ovulation, whilst the traditional POP formulations are less effective.