SICK LEAVES MOTIVATED BY SEVERE DISEASES OF OFFSPRING OF LESS THAN ONE YEAR Background: The increase in expenses of the health care system caused by sick leaves, especially those granted to mothers with children of less than one year of age with severe diseases, is a topic of concern. Aim: To describe the rates of sick leaves granted to mothers with children of less than one year of age with severe diseases from 2004 to 2008. Material and methods: Analysis of databases containing information about sick leaves coming from Chilean public and private health care subsystems. Leaves granted to mothers with sick children of less than one year were specifically analyzed in terms of days off work and the amount of monetary benefits. Results: A sustained increase, ranging from 20 to 120% in the number of sick leaves motivated by diseases of children of less than one year, was observed. Thirty four percent of maternity leaves concentrate immediately after finishing the legal period (24 weeks after birth) and almost 60% of them occured within the first 6 months after birth. The most frequent diagnoses that motivated the higher number of leaves were gastroesophageal reflux and bronchitis. Conclusions: There is probably a bad use of the benefit in a percentage of leaves. The benefit is also regressive since it favors mostly mothers of a better socioeconomic condition. The law that will extend the postnatal maternity leave will solve in part these problems.