Background
Repeated use of postcoital hormonal contraception is not currently recommended due to the higher risk of side effects and lower contraceptive effectiveness compared to other modern methods of contraception. However, emerging evidence indicates renewed interest in a regular coitally-dependent method of oral contraception. We re-evaluated the existing data on safety and effectiveness of pericoital use of levonorgestrel and other hormonal drugs to prevent pregnancy.

Objectives
To determine the effectiveness and safety of repeated use of pre- and postcoital hormonal contraception for pregnancy prevention.

Search strategy
We searched the computerized databases MEDLINE, POPLINE, CINAHL, LILACS, EMBASE and CENTRAL for trials that tested repeated pre- and postcoital use of hormonal drugs for pregnancy prevention. We also searched for current trials via ClinicalTrials.gov and ICTRP.

Selection criteria
Published and unpublished studies in any language of repeated postcoital or immediately precoital use of hormonal drugs for contraception with pregnancy as an outcome.

Data collection and analysis
Two authors independently confirmed the eligibility and extracted data from the included studies. We calculated confidence intervals (CI) around individual study Pearl indices using a Poisson distribution. We presented individual study estimates and pooled estimates and their 95% CI, where appropriate.

Main results
We found 21 trials that evaluated pericoital use of LNG and other hormonal drugs on a regular basis to prevent pregnancy. Pericoital levonorgestrel (LNG) was reasonably efficacious and safe. The pooled Pearl Index for the 0.75 mg dose of LNG was 5.1 per 100 woman-years (WY) (95% CI 3.8 to 6.7). The pooled Pearl Index for all doses of LNG was 4.9 per 100 WY (95% CI 4.3 to 5.5). Other hormonal drugs appeared promising but most of them were not studied extensively. Most women liked the pericoital method in spite of frequent menstrual irregularities.

Authors' conclusions
The studies of pericoital LNG regimens provided promising results but had a number of serious methodological limitations. A pressing need exits to conduct a rigorous research to confirm the efficacy and safety of pericoital use of LNG as a primary means of contraception among women with infrequent intercourse. If the method is shown to be efficacious, safe and acceptable, the results may warrant revision of the current WHO recommendations and marketing strategies.