Estimating the Effects of Season on Birth Outcomes
Author Information
Author(s): Linn Beate Strand, Adrian G Barnett, Shilu Tong
Primary Institution: Queensland University of Technology
Hypothesis
The study aims to demonstrate the potential size of fixed cohort bias in estimating seasonal effects on birth outcomes.
Conclusion
Retrospective birth cohort studies should account for fixed cohort bias to obtain unbiased estimates of seasonal health effects.
Supporting Evidence
- The study found strong artificial seasonal patterns in gestation length based on the end date of the study.
- After adjusting for fixed cohort bias, the effect of temperature on gestation length changed significantly.
- The adjusted cohort showed a more accurate representation of the relationship between temperature and gestation length.
Takeaway
This study shows that if researchers don't consider certain biases when looking at when babies are born, they might get the wrong idea about how seasons affect birth outcomes.
Methodology
The study simulated a retrospective birth cohort and used survival analyses to examine the effects of season and temperature on gestation length.
Potential Biases
The fixed cohort bias could lead to incorrect associations between seasonal exposures and birth outcomes.
Limitations
The study did not control for all racial groups and used ambient temperature data instead of actual temperatures experienced by women.
Participant Demographics
{"total_births":114947,"gender_distribution":{"male":59317,"female":55630},"marital_status":{"married_or_de_facto":98888,"never_married":14240,"separated_or_divorced":1788},"indigenous_status":{"indigenous":2568,"non_indigenous":112301},"smoking_status":{"non_smoker":94283,"smoker":19845},"pregnancy_complications":{"no_complications":108946,"pre_eclampsia":6001},"previous_pregnancies":{"0":34857,"1-2":55670,"3-4":17393,"5+":7027},"mean_mother_age":29.6,"mean_gestation_length_weeks":38.8}
Digital Object Identifier (DOI)
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