Emergency Contraception: A Last Chance to Prevent Unintended Pregnancy
Bibliographic record
Abstract
ABSTRACT. Emergency contraception provides women with a last chance to prevent unintended pregnancy after sex. In the United States, available options for emergency contraception are three kinds of pills (levonorgestrel, ulipristal acetate, and regular oral contraceptive pills in different doses) and the copper IUD. Of these, the copper IUD is by far the most effective, followed by ulipristal acetate and levonorgestrel pills. After years of political struggle, levonorgestrel emergency contraceptive pills are now available without age or point-of-sale restrictions on store shelves. Although emergency contraceptive pills have not been shown to reduce unintended pregnancy or abortion rates at the population level, they are an important option for women who have experienced a failure of their regular method, have not used a method, or are sexually assaulted.Keywords: emergency contraception; levonorgestrel; copper IUD; contraception; postcoital contraception; morning-after pill1. IntroductionHalf of all pregnancies in the United States are unintended: 3.2 million occurred in 2006 alone, the last year for which data are available.1 Emergency contraception offers women a last chance to prevent pregnancy after unprotected intercourse. Emergency contraception is especially important for outreach to the 4.5 million women at risk of pregnancy but not using a regular method2 by providing a bridge to use of an ongoing contraceptive method. Although emergency contraceptives do not protect against sexually transmitted infection, they do offer reassurance to the 8.6 million women who rely on condoms for protection against pregnancy2 in case of condom slippage or breakage. Emergency contraceptives available in the United States include emergency contraceptive pills and the Copper T intrauterine device (IUD).3,4'52. Emergency Contraceptive PillsThere are three types of ECPs: combined ECPs containing both estrogen and progestin, progestin-only ECPs, and ECPs containing an antiprogestin (either mifepristone or ulipristal acetate). All three are available in the United States. Progestin-only ECPs have now largely replaced the older combined ECPs because they are more effective and cause fewer side effects. Although this therapy is commonly known as the morning-after pill, the term is misleading; ECPs may be initiated sooner than the morning after - immediately after unprotected intercourse - or later - for at least 120 hours after unprotected intercourse.Combined ECPs contain the hormones estrogen and progestin. The hormones that have been studied extensively in clinical trials of ECPs are the estrogen ethinyl estradiol and the progestin levonorgestrel or norgestrel (which contains two isomers, only one of which - levonorgestrel - is bioactive). One combined, dedicated (meaning it was specially packaged for use as EC) EC product (Preven) was approved by the FDA in 1998 but withdrawn from the market in 2004. This combination of active ingredients used in this way is also sometimes called the Yuzpe method, after the Canadian physician who first described the regimen. When dedicated ECPs are not available, certain ordinary birth control pills can be used in specified combinations as emergency contraception. In either case, the regimen is one dose followed by a second dose 12 hours later, where each dose consists of 1, 2, 4, 5, or 6 pills, depending on brand. Currently, 26 brands of combined oral contraceptives are approved in the United States for use as emergency contraception (see http://ec.princeton.edU/worldwide/default.asp#country).6 Research has demonstrated the safety and efficacy of an alternative regimen containing ethinyl estradiol and the progestin norethindrone;7 this result suggests that oral contraceptive pills containing progestins other than levonorgestrel may also be used for emergency contraception.Progestin-only ECPs contain no estrogen. Only the progestin levonorgestrel has been studied for freestanding use as an emergency contraceptive. …
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.032 | 0.007 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".