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Can minimum marriageable age laws truly prevent teenage pregnancy?

The positive correlation between early marriage and early childbearing has led researchers and policy-makers to believe that curbing or prohibiting early unions can protect adolescent girls from teenage motherhood. In this article, I discuss why this is not necessarily the case, especially in societies where informal consensual unions are common.

Around the world, more than a fifth of women are married
before the age of 18. But, why is this significant and how does this relate to teenage pregnancy? Girls who are married before 18 are more likely to drop out of school, become victims of domestic abuse, and die from complications due to childbirth. Not only does this present a public health threat, but it also perpetuates the cycle of poverty as a result of the loss of human capital accumulation. In turn, this impedes sustainable development along the gender and health dimensions. 

Trends in formal and informal unions in Mexico

In Mexico, much like many other Latin American countries, the proportion of girls in informal consensual unions has been on the rise over the last 2-3 decades. At the same time, formal unions defined by marriages have declined in popularity. What this means in theory is that banning marriages below a certain age, 18 for instance, can turn out to be futile. If the share of young women in formal marriages is decreasing, it is unclear that minimum marriageable age laws will have any effect on early marriage and the associated fertility effects. 


Our study confirms this phenomenon in the context of Mexico, a middle-income developing country in Latin America. We find that while the age-of-marriage laws were effective in mitigating both formal and informal unions, they had no impact on total teenage birth rates. Yet, if one were to think about it more, these laws should have reduced teenage birth rates if they also managed to deter informal consensual unions. Digging deeper into the data, we find heterogeneous impacts showing that the age-of-marriage laws did lower teenage birth rates, but only among a specific demographic group – women living in rural areas. So, although we did not observe an impact on teenage birth rates on average, we found that the laws were effective in decreasing teenage birth rates among girls from poorer regions. 

To explain these findings, we draw upon theories related to shifts in socio-cultural norms surrounding early unions. The idea is that the minimum marriageable age laws changed poorer girls’ perceptions about entering unions at a young age, which explains the decline in not just formal unions like marriages, but also informal consensual unions. 


To sum up, prohibiting early marriage can be effective in protecting adolescent girls from the consequences of teenage pregnancy, especially those from poorer households. However, it is not likely to be as useful in preventing teenage motherhood on average as the decline in informal consensual unions and hence adolescent fertility was mainly driven by girls from poorer areas. It is therefore crucial that policy-makers supplement legal reforms with other interventions such as access to contraceptives and proper sex education, in order to protect more young women from the negative effects of early childbearing. 


Au Yong Lyn, Audrey, 2019. Prohibition without protection: Marriageable age law reforms and adolescent fertility in Mexico (No. 314). Ifo Working Paper Series. United Nations Children Emergency Fund (UNICEF), 2020. Child Marriage around the World. 11 Mar. 2020. Accessed. 17 May 2021.

Written By

Audrey Au Yong Lyn
ETH Zurich

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