hip of multiple birth and infant mortality remains significant. With all child-, maternal-, household-specific and other factors controlled, children born multiple birth were more than twice as likely to die during infancy as infants born singleton (HR = 2.19; 95% CI: 1.50, 3.19).
In the adjusted model (Table 2 – see additional file 2), with multiple birth status and other factors controlled, children born to mothers with secondary education or more were less likely to die before reaching their first birthday than children of mothers with no education (HR = 0.51; 95% CI: 0.36, 0.72). Compared to children from the poorest households, infant from the richer households are less likely to die before their first birthday (HR 0.67; 95% CI: 0.47, 0.96). None of the other risk factors or confounders has a statistically significant effect on the risk of infant mortality.
Results of this study support claims that children born multiple births are more likely to die during the first year of life as children born singletons, independent of child's sex, birth order, pregnancy care and delivery care, maternal education and nutritional status, household access to clean water and sanitation, and other factors. It is important to note that the more fully adjusted model showed a higher estimated probability of children born multiple births not to survive beyond their first birthday than the unadjusted model. This illustrate that the adjusted model was more effective in predicting the risk of infant mortality among children born multiple births, which is supported theoretically. The association between multiple birth and infant mortality has been observed not only in developing countries [7-14] but also in developed countries [15-22].
One possible reason for this observed association is that multi-foetal pregnancy and multiple births including twins and higher order multiples such as triplets and quadruplets are high-risk pregnancy and birth. These high-risk births are frequently accompanied by a number of associated foetal and neonatal complications that require special and expensive medical care . In addition, multiple-birth children are at much greater risk of birth defects and/or disabilities and accounted for larger percentage of prenatal deaths . Therefore, mortality of these high-risk groups contributes to the higher rate of childhood mortality especially during the early period of life. We also found that large majority of multiple birth children died in infancy. This is consistent with finding from previous study. The perinatal period has long been recognized as a period of increased risk for twins. . It is possible that the use of the curative services, which are needed in emergency situations, could be under-utilized by mothers of twins. However, the increased mortality risk extends into the post-neonatal and childhood period, when the mortality of twins is more than twice the value of the mortality of singletons
Consistent with previous studies [30-34], we found that mother's education has strong negative effect on infant mortality, independent of other factors. There is a very large literature from around the world that demonstrates the significance of mother's schooling to lower mortality outcome among children. The pathways from mother's schooling lower mortality rate include, but are not limited to, greater likelihood of obtaining pre- and ante-natal care, seeking prompt medical care at the first sign of a child's illness, and more appropriate breast feeding and nutritional supplementary practices. This and previous studies [14,35-40]have provided evidence that children born in the poorer households are a much greater risk of dying in infancy than children born in better-off households. Poverty affects infant survival through insufficient food intake, greater exposure to infections, and lack of access to vaccinations and basic health care.
Finally, it is necessary to discuss the limitations of this study, as well as its strengths. The present study was performed in a large nationally representative sample with stratified ra