title: Maintaining rigor in research: flaws in a recent study and a reanalysis of the relationship between state abortion laws and maternal mortality in Mexico.
abstract: A recent publication [Koch E, Chireau M, Pliego F, Stanford J, Haddad S, Calhoun B, Aracena P, Bravo M, Gatica S, Thorp J. Abortion legislation, maternal healthcare, fertility, female literacy, sanitation, violence against women and maternal deaths: a natural experiment in 32 Mexican states. BMJ Open 2015;5(2):e006013] claimed that Mexican states with more restrictive abortion laws had lower levels of maternal mortality. Our objectives are to replicate the analysis, reanalyze the data and offer a critique of the key flaws of the Koch study.
  
  
  
  We used corrected maternal mortality data (2006-2013), live births, and state-level indicators of poverty. We replicate the published analysis. We then reclassified state-level exposure to abortion on demand based on actual availability of abortion (Mexico City versus the other 31 states) and test the association of abortion access and the maternal mortality ratio (MMR) using descriptives over time, pooled chi-square tests and regression models. We included 256 state-year observations.
  
  
  
  We did not find significant differences in MMR between Mexico City (MMR=49.1) and the 31 states (MMR=44.6; p=.44). Using Koch's classification of states, we replicated published differences of higher MMR where abortion is more available. We found a significant, negative association between MMR and availability of abortion in the same multivariable models as Koch, but using our state classification (beta=-22.49, 95% CI=-38.9; -5.99). State-level poverty remains highly correlated with MMR.
  
  
  
  Koch makes errors in methodology and interpretation, making false causal claims about abortion law and MMR. MMR is falling most rapidly in Mexico City, but our main study limitation is an inability to draw causal inference about abortion law or access and maternal mortality. We need rigorous evidence about the health impacts of increasing access to safe abortion worldwide.
  
  
  
  Transparency and integrity in research is crucial, as well as perhaps even more in politically contested topics such as abortion. Rigorous evidence about the health impacts of increasing access to safe abortion worldwide is needed.
authors.affiliation: Center for Health Systems Research, National Institute of Public Health, Av. Universidad 655, Cuernavaca, Morelos, Mexico; Department of Obstetrics and Gynecology, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR, USA. Electronic address: blair.darney@insp.mx.
authors.forename: Blair G
authors.initials: BG
authors.lastname: Darney
authors.affiliation: Center for Health Systems Research, National Institute of Public Health, Av. Universidad 655, Cuernavaca, Morelos, Mexico.
authors.forename: Biani
authors.initials: B
authors.lastname: Saavedra-Avendano
authors.affiliation: Center for Health Systems Research, National Institute of Public Health, Av. Universidad 655, Cuernavaca, Morelos, Mexico; Institute for Health Metrics and Evaluation, University of Washington, 2301 5th Ave Suite 600, Seattle, WA, USA.
authors.forename: Rafael
authors.initials: R
authors.lastname: Lozano
mesh_terms: D000028:Abortion, Induced / Q000331:legislation & jurisprudence*; D000293:Adolescent; D000328:Adult; D002423:Cause of Death; D005260:Female; D006801:Humans; D016014:Linear Models; D008427:Maternal Health Services / Q000592:standards*; D008428:Maternal Mortality / Q000639:trends*; D008800:Mexico; D008875:Middle Aged; D015999:Multivariate Analysis; D011203:Poverty; D011247:Pregnancy; D012189:Retrospective Studies; D055815:Young Adult
keywords: Abortion access; Abortion legislation; Abortion research; Maternal mortality; Mexico; Scientific integrity