We exploit the Zika outbreak in Colombia in 2015 to explore how a negative shock that puts at high risk the newborn's health affects female behaviours associated with fertility, according to their marital status. The potential endogeneity of behaviours and the outbreak onset is avoided by using instrumental variables strategies in the context of an intensity-of-treatment difference-in-differences at the municipality level. While single women reduce sexual activity (the extensive margin), married women do not; instead, married women increase contraception in both the extensive margin and the intensive margin (they substitute less effective methods for more effective ones). This result is in line with a moral hazard model of fertility decisions within the couple. According to the model, not having a child may aggrieve the husband, and he may, in turn, become a "difficult" husband. In such a model, the ZIKV epidemic increases the use of women's contraception and reduces the likelihood of men's retaliation. We find no significant effects on intra-household violence exerted by men (i.e. physical and psychological violence or forced sex) nor reductions in the proportion of expenditures made by women. We do find that husbands of older women are less likely to have other sexual partners. There are heterogeneous effects across age groups and education level.
