[Underreporting of live births: measurement procedures using the Hospital Information System].

OBJECTIVE To assess underreporting of live birth records by health information systems. METHODS Secondary data of the Sistema de Informação Hospitalar (Hospital Information System - SIH) and of the Sistema de Informação de Nascidos Vivos (Information System on Live Birth - SINASC) were used in the state of Minas Gerais, Southeastern Brazil, in 2001. Two procedures were used in the analysis: the comparison between the number of live births per city and the probabilistic record linkage of individual data. For both procedures, indicators of underreporting considered were the proportion of live births presented at SIH system that were not obtained at SINASC. The municipalities were later added into four strips of population size. RESULTS The probabilistic linkage was able to identify a greater proportion of live births underreported at SINASC, relative to the comparison of live births in the municipalities. The variations of the differences among underreporting percentages per procedures were 9.4% in cities with population lower than 5,000 inhabitants; 9.1% in cities with population ranging from 5,000 and 9,999; and 8.0% in municipalities between 10,000 and 49,999 and over 50,000 inhabitants. CONCLUSIONS The amount of underreporting was sensitive to the procedures adopted. Probabilistic linkage reinforced the certainty of pairings, and also enabled to identify a greater proportion of cases not recorded at SINASC, also in greater cities. SIH was a strong indicator of underreporting of live births.