Rationale for eliminating the hormone-free interval in modern oral contraceptives

Background Although most low-dose combined oral contraceptives (COCs) include 7-day hormone-free intervals (HFIs), these COCs could incompletely suppress ovarian activity. Objectives To review the impact of HFIs on ovarian suppression and tolerability, and evaluate the utility of COCs without traditional 7-day HFIs. Search strategy PubMed was searched for clinical studies published in English between January 1980 and April 2015 on the impact of HFIs and HFI modifications in COCs. Selection criteria Articles assessing contraceptive efficacy or tolerability as the primary focus were included. Data collection and analysis Abstracts of 319 articles were screened. Results Analysis of the 161 articles selected revealed that suppression of ovarian activity with low-dose COCs with 7-day HFIs is suboptimal. Loss of ovarian suppression during 7-day HFIs is commonly associated with follicular development, and most dominant follicles appear during this period. By contrast, increased ovarian suppression was noted in regimens that shortened or eliminated the HFI, or that substituted low-dose ethinyl estradiol for the HFI. Conclusions Extended regimens with modified HFIs may provide greater ovarian suppression with the potential for increased contraceptive effectiveness. Additional research is needed to evaluate whether COC regimens that include 10 μg ethinyl estradiol instead of an HFI may improve tolerability.