Background
Over the past three decades, interventions have been implemented to reduce childhood mortality in Iran. Despite declines in overall mortality rates, inequalities in mortality across socioeconomic groups have remained unchanged. In this study, we assessed inequalities in infant mortality in rural regions of Iran.

Methods
We obtained data from the Iranian vital registration system, which includes data on 5,626,158 live births, 79,457 neonatal deaths, and 36,397 postneonatal deaths in rural areas of Iran over the course of a 16-year period, which was then divided into 4 four-year intervals. In addition to building multivariate regression models to identify factors associated with mortality, we calculated a concentration index for each province to measure inequalities in neonatal and postneonatal mortality, using wealth index as the socioeconomic variable of interest. We further assessed these inequalities as a component of their contributors by using the decomposition method.

Results
Although both neonatal (17.62 to 10.92) and postneonatal (8.11 to 5.14) mortality rates exhibited decreasing trends from 1998-2001 to 2010–2013, the inequalities observed in these indices remained nearly unchanged (concentration indices of −0.062 to −0.047 and −0.098 to −0.083, respectively). Furthermore, fraction of births occurred in hospitals and literate women contributed positively to the inequalities observed in both neonatal and postneonatal mortality rates, whereas the proportion of infants classified as low birth weight contributed negatively over all study periods. We also identified decreasing trends in inequalities of the proportion of infants classified as having low birth weight, being born in hospitals, being covered by health insurance, mothers’ age, and literacy of women within the time intervals under study.

Conclusions
Although infant mortality rates in Iran decreased over the studied time period, we observed notable inequalities in these measures. Several steps are needed to overcome these inequalities, including improving access to professional health services for lower income households, fairly distributing facilities and human resources, and improving insurance coverage to protect families from financial hardships. Moreover, social factors, such as literacy of women, were found to be important in decreasing inequalities in infant mortality. These steps require improving societal awareness of infant mortality and implementing improved and problem-oriented health policies.