Measuring and Reporting of the Treatment Effect of Hormonal Emergency Contraceptives
Bibliographic record
Abstract
STUDY OBJECTIVES: To derive summary estimates of observed pregnancy rates in women who used the Yuzpe or levonorgestrel emergency contraceptive regimen and identify the various ways in which data related to regimen effectiveness were reported, to discuss the limitations of the effectiveness estimates as they are currently reported, and to propose alternative reporting methods that are less susceptible to misinterpretation. DESIGN: Analysis of pooled data from 34 experimental or observational studies that had an explicit method of follow-up to systematically evaluate pregnancy outcome after a single course of emergency contraception treatment within a given menstrual cycle. PATIENTS: Women who took either the Yuzpe or levonorgestrel emergency contraceptive regimen to prevent pregnancy. MEASUREMENTS AND MAIN RESULTS: We searched the MEDLINE and EMBASE databases for clinical studies that systematically evaluated pregnancy outcomes of women who used the Yuzpe or levonorgestrel regimen for emergency contraception. The effectiveness of these regimens is typically reported in relative terms as the reduction of pregnancy risk from a theoretical baseline risk. We reported the effectiveness using absolute risk reductions and numbers needed to treat. We pooled relevant data by using the β-binomial method to derive observed pregnancy rates. The pooled observed pregnancy rates for studies of the Yuzpe and levonorgestrel regimens were 2.0% (95% confidence interval [CI] 1.5-2.5%) and 1.7% (95% CI 1.2-2.2%), respectively. Against expected pregnancy rates of 4-8%, relative emergency contraceptive effectiveness ranges were 50.0-75.0% and 57.5-78.8% for the Yuzpe and levonorgestrel regimens, respectively. Absolute risk reductions were 2.0-6.0% and 2.3-6.3%, respectively. This means that 17-50 women would need to have received the Yuzpe regimen and 16-43 women the levonorgestrel regimen to prevent one pregnancy. CONCLUSION: Emergency contraception effectiveness data are susceptible to misinterpretation when data are reported in relative terms without the expected pregnancy rate (i.e., the baseline risk). We recommend that the effect of emergency contraceptives be expressed in absolute terms and accompanied by the expected pregnancy rate used in its estimation.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.322 | 0.652 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.005 | 0.009 |
| Bibliometrics | 0.013 | 0.010 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
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; the direct Gemma label and the distilled Codex classifier agree on what is shown here.
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".