Differences in Risk Factors for Severe Preeclampsia and <scp>HELLP</scp> Syndrome in Singleton Versus Twin Pregnancies: A Population‐Based Cohort Study
Bibliographic record
Abstract
OBJECTIVE: To examine whether the associations between pre-pregnancy risk factors and severe preeclampsia/eclampsia (SPE) and/or HELLP syndrome differ between singleton and twin pregnancies. DESIGN: A population-based retrospective cohort study. SETTING: British Columbia (BC), Canada. POPULATION: All pregnancies with singletons or twins that resulted in a stillbirth or live birth at ≥ 20 weeks' gestation from 2008/09 to 2020/21. METHODS: Data were obtained from the BC Perinatal Database Registry. Logistic regression was used to estimate the association between each risk factor for SPE/HELLP (e.g., body-mass-index (BMI), in vitro-fertilisation (IVF), chronic hypertension, and diabetes) and the modifying effect of plurality by including interaction terms between these risk factors and plurality in the model. MAIN OUTCOME MEASURES: Severe preeclampsia, eclampsia, and/or HELLP syndrome. RESULTS: Among 563 252 pregnancies (8841 twin, 554 411 singleton), the rate of SPE/HELLP was 4.7 per 1000 singleton pregnancies and 31.1 per 1000 twin pregnancies (relative risk 6.61; 95% confidence interval (CI) 5.84-7.49). Older maternal age (≥ 35 years), nulliparity, pre-pregnancy and gestational diabetes, chronic hypertension, prior mental health problems, substance use during pregnancy, and prior stillbirth increased the odds, while smoking decreased the odds of SPE/HELLP among both singleton and twin pregnancies. However, the adjusted associations between BMI, IVF, prior abortions, and SPE/HELLP differed by plurality (interaction p-values 0.002, < 0.0001, and 0.04, respectively). IVF was associated with increased odds of SPE/HELLP in singleton pregnancies (adjusted odds ratio (aOR) 1.93; 95% CI 1.64-2.27) but not in twins (aOR 0.85; CI 0.65-1.11). Similarly, overweight BMI was associated with elevated odds in singleton pregnancies (aOR 1.47; CI 1.32-1.64) but not in twins (aOR 0.86; CI 0.59-1.25), as was obese BMI (singleton aOR 1.88; CI 1.67-2.12; twin aOR 0.80; CI 0.51-1.24). Conversely, a history of prior abortions was associated with decreased odds in twin pregnancies (aOR 0.70; CI 0.54-0.92) but not singleton pregnancies (aOR 0.95; CI 0.88-1.04). CONCLUSIONS: High BMI and IVF are associated with elevated risk of SPE/HELLP syndrome in singleton pregnancies, but not in twin pregnancies. This study provides insights regarding SPE/HELLP syndrome among singleton and twin pregnancies, and useful information for pre-pregnancy counselling.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 | 0.001 |
| 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".