Combined vaginal-cesarean delivery of twin pregnancies
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Bibliographic record
Abstract
OBJECTIVE: To estimate the incidence and factors associated with combined vaginal-cesarean delivery in twin pregnancies. METHODS: We studied all twin births weighing 500 g or more during a 20-year period (1980-1999) at a tertiary care center. Major anomalies, monoamniotic and conjoined twins, and antepartum fetal deaths were excluded. RESULTS: During this 20-year period, 105,987 women delivered, of whom 1565 (1.5%) had twins. Of these, 1151 twin sets fulfilled the study criteria. The mode of delivery was vaginal in 653 (56.8%), cesarean in 448 (38.9%), and vaginal-cesarean in 50 (4.3%). During the 20 years there was a statistically significant increase in combined vaginal-cesarean and elective cesarean deliveries, with a decrease in vaginal deliveries. Parity, gestational age, and birth weight discordance (>25%) were not associated with combined delivery. Compared with vaginal delivery, the nonvertex second twin was associated with a twofold higher risk of cesarean delivery (relative risk [RR] 2.3; 95% confidence interval [CI] 1.3, 3.8; P =.002); and an interdelivery interval of over 60 minutes with an eightfold higher risk (RR 8.2; CI 4.6,14.6; P <.001). Vaginal-cesarean delivery had a 22-fold higher use of general anesthesia compared with vaginal delivery (RR 21.8; CI 5.4, 88.5; P <.001). CONCLUSION: There has been a significant increase in combined vaginal-cesarean and elective cesarean deliveries among twin gestations, with a decrease in vaginal births. Vaginal-cesarean delivery is associated with nonvertex second twin and a prolonged interdelivery interval.
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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 | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 it