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Analyzing risks of adverse pregnancy outcomes
American Journal of Epidemiology
|November 30, 2013
Summary
Analyzing adverse pregnancy outcomes requires distinguishing time at risk from gestational age. This study clarifies risk quantification methods, addressing selection bias and the crossover paradox in perinatal death risk analysis.
Area of Science:
- Perinatal epidemiology
- Biostatistics
- Reproductive health research
Background:
- Analyzing risks for adverse pregnancy outcomes is complex and debated.
- Conflating time at risk with gestational age at birth complicates analyses.
- Existing methods may not accurately reflect etiological or prognostic questions.
Purpose of the Study:
- To clarify causal questions in analyzing adverse pregnancy outcomes.
- To differentiate between cumulative, prospective, and instantaneous risks.
- To address selection bias and the crossover paradox in perinatal death risk.
Main Methods:
- Utilizing a generic directed acyclic graph (DAG) for causal inference.
- Discussing competing risks and populations at risk with appropriate denominators.
- Decomposing gestational age-specific risk of perinatal death.
Main Results:
- Three distinct approaches to quantifying risk by gestational age are summarized.
- Failure to account for gestational age-specific risk of birth leads to selection bias.
- Selection bias explains the crossover paradox without needing unobserved confounders.
Conclusions:
- Accurate risk analysis in pregnancy outcomes necessitates careful consideration of gestational age.
- Properly defining risk numerators and denominators is crucial for valid epidemiological studies.
- Understanding selection bias is key to interpreting studies on perinatal death risk.
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