Although divorces place millions of women from poor countries into hardship, we know little
about this issue and its causes. This paper shows that the lack of children is a leading cause
for divorce. We use twins and gender of firstborns as instruments to estimate the effect of the
number of children and the existence of a son on mother’ marital statuses. The 2009 Vietnam
Population Census shows the divorce rate is 1.76 percent. We find two effects of the lack of
children on the parents’ divorce. First, an additional child reduces the divorce rate by 0.66
percentage point (equivalent to 37% of the population divorce rate). Second, the existence of
at least a son reduces the divorce rate by 0.54 percentage point (equivalent to 30% of the
population divorce rate). This massive magnitudes suggest areas for intervention to improve
women’s welfare and control the population growth.