Stillbirth in twins, exploring the optimal gestational age for delivery: a retrospective cohort study
Bibliographic record
Abstract
OBJECTIVE: To evaluate the optimal gestational age at delivery for twins. DESIGN: Retrospective cohort study. SETTING: Database containing demographic, delivery, and pregnancy outcome data for over 600,000 births from 81 hospitals in Alberta, Canada. POPULATION: All twin births in Alberta, Canada, during 1992-2007, as recorded in the databases of the Alberta Perinatal Health Project (www.aphp.ca). METHODS: The case files were reviewed for cause of death and any information regarding the gestational age at diagnosis of stillbirth. Multivariate logistic regression was used to examine the impact of potentially confounding factors. The 'fetus at risk' approach was used to evaluate the prospective risk of stillbirth. Competing risks of stillbirth and neonatal death were evaluated with a perinatal risk ratio. RESULTS: Of a total of 17,724 twin births there were 236 antepartum stillbirths, 26 intrapartum stillbirths, and 244 neonatal deaths. The rate of stillbirth peaked at 7.0/1000 fetuses at risk at 38 weeks of gestation. On multivariate analysis, small for gestational age (odds ratio, OR 2.2; 95% confidence interval, 95% CI 1.35-3.59), birthweight discrepancy >20% (OR 2.67, 95% CI 1.42-5.03), and an interaction between these two variables (OR 2.94, 95% CI 1.31-6.59), were significant. The perinatal risk ratio suggested that the risks of delivery and expectant management were balanced at 36 weeks of gestation (RR 0.6, 95% CI 0.1-5.4), but the confidence interval included one, the null value, until 38 weeks of gestation (RR 0.1, 95% CI 0.02-0.40). The majority of stillbirths at term (14/25) occurred in monochorionic diamniotic twins. The estimated risk of stillbirth in this group was 2.3/1000 fetuses at risk at 37 weeks of gestation, and 17.4/1000 fetuses at risk at 38 weeks of gestation. CONCLUSIONS: The balance of risk between neonatal death/intrapartum stillbirth and antepartum stillbirth begins to favour delivery at 36 weeks of gestation, particularly in monochorionic diamniotic twins.
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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 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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; 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".