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

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 (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 (R(2)) 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.

Keywords: EPIDEMIOLOGY; GYNAECOLOGY; OBSTETRICS; PUBLIC HEALTH.

Figure 1

Mortality ratios and the proportion of abortion-related deaths by place of residence in states with less and more permissive abortion legislation. Line charts illustrate trends in MMR (top-left panel), MMR_AO (top-right panel), iAMR (bottom-left panel) and the proportion of abortion-related deaths (bottom-right 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 Materials and methods). For comparison, trends for the whole Mexican country (all states) are depicted as dotted lines. Bar charts show average ratios and proportions 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. iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMR_AO, MMR 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. Line charts illustrate trends in MMR (top-left panel), MMR_AO (top-right panel), iAMR (bottom-left panel) and the proportion of abortion-related deaths (bottom-right 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 Materials and methods). For comparison, trends for the whole Mexican country (all states) are depicted as dotted lines. Bar charts show average ratios and proportions 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. iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMR_AO, MMR 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 their criminal code (see Materials and methods). Increasing blue colour indicates an increase in MMR or iAMR on a quintile or quartile scales (see the legend of each panel). 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. Line charts illustrate trends for MMR (top-left panel), MMR_AO (top-right panel), iAMR (bottom-left panel) and the proportion of abortion-related deaths (bottom-right 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 Materials and methods). Bar charts show average ratios and proportions of abortion-related deaths for each group (dark green and cyan bars, respectively). *p<0.05 using a Z-test. iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMR_AO, MMR 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. Line charts illustrate trends for MMR (top-left panel), MMR_AO (top-right panel), iAMR (bottom-left panel) and the proportion of abortion-related deaths (bottom-right 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 (see online supplementary figure S1). Bar charts show average ratios and proportions of abortion-related deaths for each group (dark green and cyan bars, respectively). *p<0.05 using Z-test. iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMR_AO, MMR with abortive outcome.

Figure 6

Mortality ratios and proportions of abortion-related deaths by place of residence in states with or without constitutional amendment to protect the unborn starting at conception: focus on the Federal District. Line charts illustrate trends for MMR (top-left panel), MMR_AO (top-right panel), iAMR (bottom-left panel) and the proportion of abortion-related deaths (bottom-right 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 (hatched) 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 (see online supplementary figure S1). Bar charts show average ratios and proportions of abortion-related deaths for each group (dark green, cyan and hatched bars, respectively). *p<0.05 using Z-test. iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMR_AO, MMR with abortive outcome.

Figure 7

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: focus on the Federal District. Line charts illustrate trends for MMR (top-left panel), MMR_AO (top-right panel), iAMR (bottom-left panel) and the proportion of abortion-related deaths (bottom-right 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 (hatched) 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 (see online supplementary figure S1). Bar charts show average ratios and proportions of abortion-related deaths for each group (dark green, cyan and hatched bars, respectively). *p<0.05 using Z-test. iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMR_AO, MMR 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. iAMR, induced abortion mortality ratio; MMR, maternal mortality ratio; MMR_AO, MMR with abortive outcome; TFR, total fertility rate.