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BMJ Open 2015;5:e006013 doi:10.1136/bmjopen-2014-006013

• Epidemiology

Abortion legislation, maternal healthcare, fertility, female literacy, sanitation, violence against women and maternal deaths: a natural experiment in 32 Mexican states

1. Elard Koch1, 
2. Monique Chireau2, 
3. Fernando Pliego3, 
4. Joseph Stanford4, 
5. Sebastian Haddad5, 
6. Byron Calhoun6, 
7. Paula Aracena1, 
8. Miguel Bravo1, 
9. Sebastián Gatica1, 
10. John Thorp7,8

+Author Affiliations

1. ¹Division of Epidemiology, MELISA Institute, Concepción, Chile
2. ²Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, USA
3. ³Instituto de Investigaciones Sociales, Universidad Nacional Autónoma de México, Av Universidad 3000, Copilco Universidad, Ciudad de México, Mexico
4. ⁴Division of Public Health, Department of Family and Preventive Medicine, University of Utah School of Medicine, Salt Lake City, USA
5. ⁵Coordinación de Investigación, Facultad de Ciencias de la Salud, Universidad Anáhuac, Estado de México, Mexico
6. ⁶Department of Obstetrics and Gynecology, West Virginia University, Morgantown, USA
7. ⁷Department of Obstetrics and Gynecology, University of North Carolina-Chapel Hill, Chapel Hill, USA
8. ⁸Center for Women's Health Research, University of North Carolina School of Medicine, Chapel Hill, USA

1. Correspondence toDr Elard Koch; ekoch@melisainstitute.org

• Received 1 July 2014
• Revised 28 November 2014
• Accepted 2 December 2014
• Published 23 February 2015

Abstract

Objective To test whether there is an association between abortion legislation and maternal mortality outcomes after controlling for other factors thought to influence maternal health.

Design Population-based natural experiment.

Setting and data sources Official maternal mortality data from 32 federal states of Mexico between 2002 and 2011.

Main outcomes Maternal mortality ratio (MMR), MMR with any abortive outcome (MMR_AO) and induced abortion mortality ratio (iAMR).

Independent variables Abortion legislation grouped as less (n=18) or more permissive (n=14); constitutional amendment protecting the unborn (n=17); skilled attendance at birth; all-abortion hospitalisation ratio; low birth weight rate; contraceptive use; total fertility rates (TFR); clean water; sanitation; female literacy rate and intimate-partner violence.

Main results Over the 10-year period, states with less permissive abortion legislation exhibited lower MMR (38.3 vs 49.6; p<0.001), MMR_AO (2.7 vs 3.7; p<0.001) and iAMR (0.9 vs 1.7; p<0.001) than more permissive states. Multivariate regression models estimating effect sizes (β-coefficients) for mortality outcomes showed independent associations (p values between 0.001 and 0.055) with female literacy (β=−0.061 to −1.100), skilled attendance at birth (β=−0.032 to −0.427), low birth weight (β=0.149 to 2.166), all-abortion hospitalisation ratio (β=−0.566 to −0.962), clean water (β=−0.048 to −0.730), sanitation (β=−0.052 to −0.758) and intimate-partner violence (β=0.085 to 0.755). TFR showed an inverse association with MMR (β=−14.329) and MMR_AO (β=−1.750) and a direct association with iAMR (β=1.383). Altogether, these factors accounted for (R²) 51–88% of the variance among states in overall mortality rates. No statistically independent effect was observed for abortion legislation, constitutional amendment or other covariates.

Conclusions Although less permissive states exhibited consistently lower maternal mortality rates, this finding was not explained by abortion legislation itself. Rather, these differences were explained by other independent factors, which appeared to have a more favourable distribution in these states.