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Association of US state policy orientation with adverse birth outcomes: a longitudinal analysis
  1. Alicia R Riley1,
  2. Daniel Collin2,
  3. Jacob M Grumbach3,
  4. Jacqueline M Torres1,
  5. Rita Hamad2
  1. 1Epidemiology & Biostatistics, University of California San Francisco, San Francisco, California, USA
  2. 2Family Community Medicine, University of California San Francisco, San Francisco, California, USA
  3. 3Political Science, University of Washington, Seattle, Washington, USA
  1. Correspondence to Dr Alicia R Riley, Epidemiology & Biostatistics, University of California San Francisco, San Francisco, California, USA; alicia.riley{at}


Background The current US context is marked by extreme right–left partisanship, which means that state policies tend to bundle together and are not experienced in isolation. While prior work has leveraged abrupt shifts in single policies to examine the effects of state policy on birth outcomes, we examined a holistic measure that captures political polarisation.

Methods Data were drawn from national birth certificates for 2003–2017 (N=56 770 470). Outcomes included preterm birth, low birth weight, small-for-gestational age and other perinatal health measures. The primary exposure was a composite index of right–left state policy orientation, generated from historical data on 135 state policies. Multivariable regressions were used to estimate the association between state policy orientation and each outcome, adjusting for relevant covariates.

Results Compared with infants born in states with right-leaning policy orientations, those born in left-leaning states had lower odds of adverse birth outcomes (eg, low birth weight: OR 0.95 (0.93, 0.97), preterm birth: OR 0.94 (0.92, 0.95)). Subgroup analyses revealed stronger associations for US-born and White mothers. With the inclusion of state fixed effects, left-leaning policy orientation was no longer associated with lower odds of adverse birth outcomes. Models were otherwise robust to alternative specifications.

Conclusion While left-leaning state policy orientation has protective associations with a range of birth outcomes, the associations may be explained by stable characteristics of states, at least during the study period. Future studies should examine state policy orientation in association with other health outcomes and study periods.

  • birth weight
  • perinatal epidemiology
  • policy

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  • Twitter @aliciacita, @DrRitaHamad

  • Contributors ARR led the writing and assisted with interpretation of results. DC completed the analyses and created figures and tables. JMG created the exposure variable and assisted with interpretation of results. JMT assisted with the study design and interpretation of results. RH conceived and supervised the study and writing. All authors contributed to revising the manuscript critically for intellectual content and approved of the final submitted version.

  • Funding ARR’s work is supported by a training grant from the NIA: T32AG049663; RH's, DC’s and JMT’ work is supported by the UCSF California Preterm Birth Initiative and a grant from the NHLBI: K08HL132106.

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  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval This study was approved by the institutional review board at University of California San Francisco (protocol number 18-26719).

  • Data availability statement Birth certificate data are restricted and were made available through a Data Use Agreement with the National Center for Health Statistics.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.