El uso repetido de la anticoncepción hormonal pre y poscoital para la prevención del embarazo

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 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 METHODS:

We searched until 1 September 2014 for trials that tested repeated pre- and postcoital use of hormonal drugs for pregnancy prevention. Databases included CENTRAL, MEDLINE, and POPLINE. We searched for current trials via ClinicalTrials.gov and ICTRP. For the initial review, we also searched EMBASE, CINAHL, and LILACS, and wrote to researchers to identify other trials.

SELECTION CRITERIA:

We considered published and unpublished studies of repeated postcoital or immediately precoital use of hormonal drugs for contraception with pregnancy as an outcome.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 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 22 trials that evaluated pericoital use of LNG and other hormonal drugs on a regular basis to prevent pregnancy. The studies included a total of 12,400 participants, and were conducted in Europe, Asia, and the Americas. The drugs and doses evaluated included levonorgestrel (LNG) 0.75 mg (11 studies), LNG in doses other than 0.75 mg (4 trials), and hormones other than LNG (7 trials). Outcomes included pregnancy rates, discontinuation, side effects, and acceptability.
Pericoital levonorgestrel was reasonably efficacious and safe. The pooled Pearl Index for the 0.75 mg dose of LNG was 5.4 per 100 woman-years (95% CI 4.1 to 7.0). The pooled Pearl Index for all doses of LNG was 5.0 per 100 woman-years (95% CI 4.4 to 5.6). Other hormonal drugs appeared promising but most of them were not studied extensively. Menstrual irregularities were the most common side effects reported. However, the studies provided no consistent evidence of a relationship between bleeding abnormalities and either frequency of pill intake or total dose of the drug. Non-menstrual side effects were reportedly mild and not tabulated in most studies. Most women liked the pericoital method in spite of frequent menstrual irregularities.

AUTHORS' CONCLUSIONS:

The studies of pericoital LNG regimens provided promising results but many had serious methodological issues. Most reports were decades old and provided limited information. However, we considered the evidence to be moderate quality because of the large number of participants from diverse populations, the low pregnancy rates, and the consistent results across studies. Rigorous research is still needed 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 World Health Organization recommendations and marketing strategies.