Association between interpregnancy interval and subsequent stillbirth in 58 low-income and middle-income countries: a retrospective analysis using Demographic and Health Surveys
Bibliographic record
Abstract
BACKGROUND: About 3 million stillbirths occur each year, 98% of which are in low-income and middle-income countries (LMICs). Interpregnancy interval is a key risk factor of interest, because it is modifiable. We aimed to investigate whether there is a causal relationship between the length of interpregnancy interval and risk of subsequent stillbirth. METHODS: We used Demographic and Health Surveys (2002-18) from 58 LMICs to study reproductive histories of women and to identify livebirths and stillbirths in the preceding 5 years. Countries were selected on the basis of the availability of interpregnancy interval data and other covariates of interest (age, education, urban or rural residence, and wealth) in surveys done since 2002. Exclusion criteria were being nulliparous, having missing parity data, and not having had at least two births (livebirth or stillbirth) in the 5 years before the survey. We combined two analytic approaches: one that analyses intervals between all births and another that analyses intervals within mothers. We report stratified estimates for the first, second, and third intervals, controlling for all past birth outcomes and intervals in a 5-year period, and other socioeconomic covariates. We also explored effect heterogeneity across key cohort subgroups. FINDINGS: Between July, 1997, and April, 2018, we identified 716 478 births from 338 223 women in 123 Demographic and Health Surveys from 58 LMICs, of which 9647 were stillbirths. Intervals of less than 6 months were associated with an increased risk of stillbirth in the between-mother models when considering the first interval (risk difference [RD] 0·0096, 95% CI 0·008-0·011). This association was slightly attenuated when considering only the second interval (RD 0·0054, 95% CI 0·0010 to 0·0099) and substantially attenuated when considering only the third interval (0·0007, -0·037 to 0·039). Within-mother modelling showed a null association with intervals of 24-59 months when considering the first and second (RD 0·007, 95% CI -0·001 to 0·016) and first and third (0·040, -0·422 to 0·501) intervals. INTERPRETATION: Although interpregnancy intervals of less than 12 months were associated with increased risk of stillbirth, these effects were attenuated when considering second and third intervals, suggesting the association in the first interval might not be causal. Future studies should use generalisable cohorts with longitudinal data, and report estimates stratified by birth order. FUNDING: Canadian Institutes of Health Research.
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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 | 0.003 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 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".