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 (MMRAO) 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), MMRAO (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 MMRAO (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.
Table 1
Current abortion legislations based on criminal exemptions from prosecution of abortion in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation.
Table1.xls
Table 2
Average change per year in different maternal mortality outcomes by place of residence and occurrence in groups of Mexican states with more or less permissive abortion legislation and the entire country (2002-2011) based on Autoregressive Integrated Moving Average (ARIMA) models.
Table2.xls
Table 3
Comparative analysis of average mortality outcomes by residence and occurrence for groups of Mexican states exhibiting a more or less permissive abortion legislation, 2002-2011.
Table3.xls
Table 4
Comparative analysis of average mortality outcomes by residence and occurrence for groups of states with or without constitutional amendment protecting the unborn from conception, 2008-2011.
Table4.xls
Table 5
Independent variables in each Mexican state: frequencies and analyses of normal distribution.
Table5.xls
Table 6
Univariate associations between 10 independent variables and maternal mortality outcomes for 32 Mexican states, 2002-2011.
Table6.xls
Table 7
Explanatory models for trends on maternal mortality ratio (MMR), maternal mortality ratio with an abortive outcome (MMRAO), and induced abortion mortality ratio (iAMR) in 32 Mexican states after refinement, 2002-2011.
Table7.xls
Table 8
Alternative explanatory regression models for MMR, MMRAO and iAMR after refinement considering independent variables excluded from the explanatory models because of collinearity.
Table8.xls
Table 9
Comparison of different indicators of maternal healthcare and human development between groups of states with less and more permissive abortion legislation.
Table9.xls
Box 1
Evidence-based public health interventions to improve maternal health in Mexico.
Box1.xls
Table S1
Detailed description of independent variables considered in the natural experiment of 32 Mexican states on maternal mortality outcomes.
TableS1.xls
Table S2
Observed live births by place of residence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS2.xls
Table S3
Observed live births by place of occurrence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS3.xls
Table S4
Total maternal deaths by place of residence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS4.xls
Table S5
Maternal deaths with abortive outcome by place of residence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS5.xls
Table S6
Induced abortion-related deaths by place of residence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS6.xls
Table S7
Total maternal deaths by place of occurrence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS7.xls
Table S8
Maternal deaths with abortive outcome by place of occurrence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS8.xls
Table S9
Induced abortion-related deaths by place of occurrence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS9.xls
Table S10
Maternal mortality ratio (MMR) by place of residence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS10.xls
Table S11
Maternal mortality ratio with abortive outcome (MMRAO) by place of residence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS11.xls
Table S12
Induced abortion mortality ratio (iAMR) by place of residence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS12.xls
Table S13
Maternal mortality ratio (MMR) by place of occurrence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS13.xls
Table S14
Maternal mortality ratio with abortive outcome (MMRAO) by place of occurrence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS14.xls
Table S15
Induced abortion mortality ratio (iAMR) by place of occurrence in 32 Mexican states exhibiting a more (m) or less (l) permissive abortion legislation, 2002-2011.
TableS15.xls
Table S16
Explanatory models for trends on maternal mortality ratio (MMR), maternal mortality ratio with an abortive outcome (MMRAO), and induced abortion mortality ratio (iAMR) in 32 Mexican states before refinement, 2002-2011.
TableS16.xls
Figure 1
Mortality ratios and the proportion of abortion-related deaths by place of residence in states with less and more permissive abortion legislation. Left panels illustrate trends in MMR (top panel), MMRAO (middle top panel), iAMR (middle bottom panel), and the proportion of abortion-related deaths (bottom panel) by place of residence between 2002 and 2011 in Mexican states, grouped as with less permissive (in dark green) or more permissive (in cyan) in terms of abortion legislation in their criminal code (see Material and Methods). For comparison, trends for the whole Mexican country (all states) are depicted as dotted lines. Right panels show average ratios and proportion of abortion-related deaths for each group (dark green and cyan bars, respectively), and the whole Mexican country (hollow bars). * p<0.05 using Z-test. Abbreviations: iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMRAO, maternal mortality ratio with an abortive outcome.
Figure 2
Mortality ratios and the proportion of abortion-related deaths by place of occurrence in states with less and more permissive abortion legislation. Left panels illustrate trends in MMR (top panel), MMRAO (middle top panel), iAMR (middle bottom panel), and the proportion of abortion-related deaths (bottom panel) by place of occurrence between 2002 and 2011 in Mexican states, grouped as with less permissive (in dark green) or more permissive (in cyan) in terms of abortion legislation in their criminal code (see Material and Methods). For comparison, trends for the whole Mexican country (all states) are depicted as dotted lines. Right panels show average ratios and proportion of abortion-related deaths for each group (dark green and cyan bars, respectively), and the whole Mexican country (hollow bars). * p<0.05 using Z-test. Abbreviations: iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMRAO, maternal mortality ratio with abortive outcome.
Figure 3
Average mortality ratios in states with more or less permissive abortion legislation between 2002 and 2011. Political maps of Mexican states are shown for average MMR (top panel) and average iAMR (bottom panel) for the 2002-2011 period, indicating whether they exhibit less (orange dots) or more (yellow dots) permissive abortion legislation, in terms of abortion legislation in their criminal code (see Material and Methods). Increasing blue colour indicates an increase in MMR or iAMR, on a quintile scale (see legend of each panel). Abbreviations: Ag., Aguascalientes; Co., Colima; FD., Federal District; iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; Mo., Morelos; Tl., Tlaxcala.
Figure 4
Mortality ratios and the proportion of abortion-related deaths by place of residence in states with or without a constitutional amendment to protect the unborn starting at conception. Left panels illustrate trends for MMR (top panel), MMRAO (middle top panel), iAMR (middle bottom panel), and the proportion of abortion-related deaths (bottom panel) by place of residence between 2008 and 2011 in Mexican states, grouped as with amendment (in dark green) or without amendment (in cyan) in terms of abortion legislation in their criminal code (see Material and Methods). Right panels show average ratios and proportion of abortion-related deaths for each group (dark green and cyan bars, respectively). * p<0.05 using Z-test. Abbreviations: iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMRAO, maternal mortality ratio with abortive outcome.
Figure 5
Mortality ratios and the proportion of abortion-related deaths by place of occurrence in states with or without a constitutional amendment to protect the unborn starting at conception. Left panels illustrate trends for MMR (top panel), MMRAO (middle top panel), iAMR (middle bottom panel), and the proportion of abortion-related deaths (bottom panel) by place of occurrence between 2008 and 2011 in Mexican states, grouped as with amendment (in dark green) or without amendment (in cyan) in terms of exhibiting or not a constitutional amendment to protect the unborn starting at conception (Figure S1, Supplementary Material). Right panels show average ratios and proportion of abortion-related deaths for each group (dark green and cyan bars, respectively). * p<0.05 using Z-test. Abbreviations: iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMRAO, maternal mortality ratio with abortive outcome.
Figure 6
Mortality ratios and the proportion of abortion-related deaths by place of residence in states with or without a constitutional amendment to protect the unborn starting at conception: focus on the Federal District. Left panels illustrate trends for MMR (top panel), MMRAO (middle top panel), iAMR (middle bottom panel), and the proportion of abortion-related deaths (bottom panel) by place of residence between 2008 and 2011 in Mexican states, grouped as with amendment” (in dark green), without amendment (in cyan), and the Federal District (in green) in terms of exhibiting or not an constitutional amendment (the Federal District of Mexico was not included in this group to be illustrated separately) to protect the unborn starting at conception (Figure S1, Supplementary Material). Right panels show average ratios and proportion of abortion-related deaths for each group (dark green, cyan, and green bars, respectively). * p<0.05 using Z-test. Abbreviations: iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMRAO, maternal mortality ratio with abortive outcome.
Figure 7
Mortality ratios and the proportion of abortion-related deaths by place of occurrence in states with or without constitutional amendment to protect the unborn starting at conception: focus on the Federal District. Left panels illustrate trends for MMR (top panel), MMRAO (middle top panel), iAMR (middle bottom panel), and the proportion of abortion-related deaths (bottom panel) by place of occurrence between 2008 and 2011 in Mexican states, grouped as with amendment (in dark green), without amendment (in cyan), and the Federal District (in green) in terms of exhibiting or not a constitutional amendment (the Federal District of Mexico was not included in this group to be illustrated separately) to protect the unborn starting at conception (Figure S1, Supplementary Material). Right panels show average ratios and proportion of abortion-related deaths for each group (dark green, cyan, and green bars, respectively).
* p<0.05 using Z-test. Abbreviations: iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMRAO, maternal mortality ratio with abortive outcome.
Figure 8
Proportional contribution of independent variables to observed differences in maternal mortality outcomes among Mexican states in primary and alternative multivariate regression models.
Abbreviations: iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMRAO, maternal mortality ratio with abortive outcome.
Figure S1
Mexican states with and without constitutional amendment to protect the unborn starting at conception between 2008 and 2011. Political maps of Mexican states are shown for 2008 (top panel), 2009 (middle panel), and 2010 (bottom panel), indicating whether they exhibit a constitutional amendment to protect the unborn starting at conception1 in dark green (with amendment) and cyan (without amendment). The state of Chihuahua enacted its political constitution in 1994; Baja California, Morelos, and Sonora in 2008; Campeche, Chiapas, Colima, Durango, Guanajuato, Jalisco, Nayarit, Oaxaca, Puebla, Querétaro, Quintana Roo, San Luis Potosí, and Yucatán in 2009; and Tamaulipas in 2010. Campeche revoked the amendment in 2010. Ag, Aguascalientes; Co, Colima; FD, Federal District; Mo, Morelos; Tl, Tlaxcala.