Mechanism of action of levonorgestrel emergency contraception.

There has been much debate regarding levonorgestrel emergency contraception's (LNG-EC's) method of action since 1999 when the Food and Drug Administration first approved its use. Proponents of LNG-EC have argued that they have moral certitude that LNG-EC works via a non-abortifacient mechanism of action, and claim that all the major scientific and medical data consistently support this hypothesis. However, newer medical data serve to undermine the consistency of the non-abortifacient hypothesis and instead support the hypothesis that preovulatory administration of LNG-EC has significant potential to work via abortion. The implications of the newer data have important ramifications for medical personnel, patients, and both Catholic and non-Catholic emergency room protocols. In the future, technology such as the use of early pregnancy factor may have the potential to quantify how frequently preovulatory LNG-EC works via abortion. Lay Summary: How Plan B (levonorgestrel emergency contraception) works has been vigorously debated ever since the Food and Drug Administration approved it in 1999. Many doctors and researchers claim that it has either no-or at most-an extremely small chance of working via abortion. However, the latest scientific and medical evidence now demonstrates that levonorgestrel emergency contraception theoretically works via abortion quite often. The implications of the newer data have important ramifications for medical personnel, patients, and both Catholic and non-Catholic emergency room rape protocols.

Oral contraceptive use as a risk factor for premenopausal breast cancer: a meta-analysis.

OBJECTIVE: To perform a meta-analysis of case-control studies that addressed whether prior oral contraceptive (OC) use is associated with premenopausal breast cancer. METHODS: We searched the MEDLINE and PubMed databases and bibliography reviews to identify case-control studies of OCs and premenopausal breast cancer published in or after 1980. Search terms used included breast neoplasms, oral contraceptives, contraceptive agents, and case-control studies. Studies reported in all languages were included. Thirty-four studies were identified that met inclusion criteria. Two reviewers extracted data from original research articles or additional data provided by study authors. We used the DerSimonian-Laird method to compute pooled odds ratios (ORs) and confidence intervals (CIs) and the Mantel-Haenszel test to assess association between OC use and cancer. RESULTS: Use of OCs was associated with an increased risk of premenopausal breast cancer in general (OR, 1.19; 95% CI, 1.09-1.29) and across various patterns of OC use. Among studies that provided data on nulliparous and parous women separately, OC use was associated with breast cancer risk in both parous (OR, 1.29; 95% CI, 1.20-1.40) and nulliparous (OR, 1.24; 95% CI, 0.92-1.67) women. Longer duration of use did not substantially alter risk in nulliparous women (OR, 1.29; 95% CI, 0.85-1.96). Among parous women, the association was stronger when OCs were used before first full-term pregnancy (FFTP) (OR, 1.44; 95% CI, 1.28-1.62) than after FFTP (OR, 1.15; 95% CI, 1.06-1.26). The association between OC use and breast cancer risk was greatest for parous women who used OCs 4 or more years before FFTP (OR, 1.52; 95% CI, 1.26-1.82). CONCLUSION: Use of OCs is associated with an increased risk of premenopausal breast cancer, especially with use before FFTP in parous women.

Postfertilization effect of hormonal emergency contraception.

OBJECTIVE: To assess the possibility of a postfertilization effect in regard to the most common types of hormonal emergency contraception (EC) used in the US and to explore the ethical impact of this possibility. DATA SOURCES AND STUDY SELECTION: A MEDLINE search (1966-November 2001) was done to identify all pertinent English-language journal articles. A review of reference sections of the major review articles was performed to identify additional articles. Search terms included emergency contraception, postcoital contraception, postfertilization effect, Yuzpe regimen, levonorgestrel, mechanism of action, Plan B. DATA SYNTHESIS: The 2 most common types of hormonal EC used in the US are the Yuzpe regimen (high-dose ethinyl estradiol with high-dose levonorgestrel) and Plan B (high-dose levonorgestrel alone). Although both methods sometimes stop ovulation, they may also act by reducing the probability of implantation, due to their adverse effect on the endometrium (a postfertilization effect). The available evidence for a postfertilization effect is moderately strong, whether hormonal EC is used in the preovulatory, ovulatory, or postovulatory phase of the menstrual cycle. CONCLUSIONS: Based on the present theoretical and empirical evidence, both the Yuzpe regimen and Plan B likely act at times by causing a postfertilization effect, regardless of when in the menstrual cycle they are used. These findings have potential implications in such areas as informed consent, emergency department protocols, and conscience clauses.