The Northwestern twin chorionicity study: testing the ‘placental crowding’ hypothesis
Bibliographic record
Abstract
OBJECTIVE: To evaluate the relation between placental proximity and frequency of birth weight discordance and small-for-gestational age (SGA) infants. STUDY DESIGN: Retrospective three-tier chorionicity analysis of 1155 twin placentas comparing birth weight characteristics of the twins in different placental types. RESULTS: Dichorionic-separate, but not dichorionic-fused twins, are heavier than monochorionic-diamniotic and monoamniotic twins (2376+/-721 vs. 2274+/-770, P < 0.006, and 2376+/-721 vs. 2166+/-782, P < 0.04). SGA twins are less frequent among dichorionic twins (OR 0.4; 95% CI 0.3, 0.6). Fewer sets with two SGA infants are present among dichorionic-separate compared to monochorionic-diamniotic pairs (OR 0.3; 95% CI 0.1, 0.8). The same trends are found when comparing all dichorionic to all monochorionic twins. Twins of all placental types have similar gestational ages and discordance values. CONCLUSIONS: Dichorionic-separate placentas are least likely to experience 'placental crowding' and thus are associated with heavier twins and fewer sets with one or two SGA infants.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".