Re: “Preterm Delivery Rates in North Carolina: Are They Really Declining among Non-Hispanic African Americans?”
Bibliographic record
Abstract
Vahratian et al. (1) conclude that the recently observed decline in preterm birth among non-Hispanic African Americans in North Carolina is an artifact related to temporal reductions in the misclassification of full-term births (as preterm births). We are concerned that the bimodal birth weight distribution problem identified by Vahratian et al. (1) in 1989 was observed at 28–31 weeks' gestation but not at 32–36 weeks. This is important, because most of the decline in preterm birth among non-Hispanic African Americans in North Carolina and the United States (2–4) was observed at 32–36 weeks' gestation (from 14.4 percent in 1989 to 12.9 percent in 1999 (1)) rather than at 28–31 weeks' gestation (from 2.2 percent in 1989 to 1.9 percent in 1999 (1)). More importantly, our recent studies of singletons (5) and twins (6) show that changes in preterm birth between 1989 and 2000 among Blacks in the United States have been primarily influenced by declines in spontaneous preterm birth and preterm birth following ruptured membranes. Over the same period, there has also been a concurrent, substantial increase in medically indicated preterm birth among Blacks (5, 6). These patterns provide at least a partial explanation for the rising rates of preterm birth among Black livebirths with birth weights less than 2,500 g (the other piece of evidence offered by Vahratian et al. (1)). Medically indicated preterm birth is associated with a much higher rate of growth restriction than spontaneous preterm birth and preterm birth following ruptured membranes (e.g., small-for-gestational-age rates of 22.3 percent vs. 8.0 percent and 8.6 percent, respectively (7)). Thus, the restriction to preterm births with birth weights less than 2,500 g would have largely resulted in a focus on trends in medically indicated preterm birth. It is also noteworthy that the restriction to preterm births of <2,500 g is excessively stringent (the 50th percentiles of birth weight for gestational age at 34, 35, and 36 weeks are 2,667 g, 2,831 g, and 2,974 g, respectively, according to the US reference standard for fetal growth (8)). The use of a more appropriate criterion for excluding misclassified full-term births—such as the exclusion of preterm livebirths with a birth weight higher than the 90th percentile of birth weight for gestational age (8)—would show that preterm birth among non-Hispanic African Americans in the United States declined from 1989 to 1999.
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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 | 0.004 | 0.023 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.008 | 0.002 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.043 | 0.038 |
| Insufficient payload (model declined to judge) | 0.010 | 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".