2.1. Underfive Mortality Rate
Globally, approximately 5.6 million deaths of children under five years of age (under five deaths) have been reported. Of these deaths, three million occurred between 1 and 59 months of age, while the remainder occurred between birth and the first month of life [18]. An analysis of the Bhutan National Health Survey 2012 showed that Bhutan’s UFM rate was 59 per 1000 live births [22]. Evidence from the Nepal Demographic and Health Survey (2001–2016) indicated a U5MR of 104 per 1000 live births [18]. In Ethiopia, it was approximately 67 per 1000 live births from the 2016 Nationwide Survey Data analysis; 4.1, 52.3 and 3.2 deaths per 1000 live births were attributable to being born to mothers aged <15, 15-25 and >25 years when they first gave birth, respectively [23].
2.2. Factors Associated with Underfive Mortality
2.2.1. Socioeconomic Factors
2.2.1. 1. Mother’s education
Maternal education, especially secular education, is the single most important factor for improved child survival [20]. In a study conducted in 2015, the mean years of schooling showed a significant correlation with the decrease in mortality rates, meaning that as the education level increased, the health literacy of women rose as well, which led to better health, better care of their children, and more attention of women to the health of their family, thus reducing mortality and morbidity in West and South Asian countries [1]. Children of mothers with no schooling had 1.88 times higher mortality than those whose mothers had six or more years of schooling in Bangladesh [19]. The U5MR was found to be significantly lower among children born to parents who attended at least a high school education in Bhutan [22]. The odds of UFM were significantly lower, 62% and 77%, among children whose fathers had a high school and tertiary level of education, respectively, and 69% lower among those whose household head had received a high school education [22].
For instance, in South Africa, falling behind in school was the strongest risk factor for giving birth within the following two years [11]. The study results in Nigeria showed that the risk of childhood mortality is 26.7%, 39.7 and 45.9% lower among mothers with primary, secondary and tertiary education, respectively, than among those with no formal education [24]. One of the pathways by which mothers’ education affects child survival is through improved child care [25]. This is probably because those with little education before marriage may be unable or poorly equipped to make appropriate reproductive health decisions that are important in reducing pregnancy-related complications [26]. Increased schooling has been associated with better health of women and their children in Zambia [13]. An analysis of the 2011 EDHS data reveals that the risk of dying for a child born to an uneducated mother was 2.13 times higher compared to a child whose mother had primary and higher education. Additionally, in Gilgel Gibe’s field research of determinants of UFM, children born to mothers whose educational level was below elementary were 14 times more likely to die than children whose mothers’ education was above elementary [25]. Similarly, evidence from EDHS 2016 data analysis suggests that deaths among underfive children differed significantly with the level of mothers’ education, with those of relatively higher education having a lower chance of experiencing underfive deaths (P value < 0.001) [14]. Children born to a mother with no education at all were associated with a 2.61 times increased risk of underfive deaths compared to being born to a mother with higher education (OR=2.610, 95% CI: 1.598, 4.265); children from mother with only primary education were 2.27 times more likely to be at the risk of underfive mortality (OR=2.271, 95% CI: 1.398, 3.687), while children born to mother with secondary education were 2.163 times more likely to die before celebrating their fifth birthday (OR=2.163, 95% CI: 1.184, 3.534) compared to being born to mother with higher education, keeping all other covariates constant [14]. Evidence from the Kersa HDSS in the Kersa district of Eastern Hararghe, Oromia, Ethiopia, also shows that maternal educational status was significantly associated with underfive children’s mortality (OR 1.31 (1.13, 1.49)) [27].
2.2.1. 2. Income
Children from low asset category households had, on average, a 1.17 times higher mortality rate than those from high asset category households in Bangladesh [20]. The odds of UFM decreased significantly with increasing wealth quintiles and were lower among those born to working mothers [22]. The risk of childhood mortality was significantly lower in the middle, richer and richest (11.1%, 37.5 and 49%) economic quintiles, respectively, when compared to the risk of childhood mortality with a female spouse who is the poorest in Nigeria [24]. Low empowerment, indicated by low income and low decision-making power, is significantly associated with the likelihood of experiencing pregnancy complications in the study area, as those with low empowerment are (OR 3.962, CI 0.937-1.083, P<0.005) more likely to experience complications when compared with other categories [26]. Evidence from the Kersa HDSS in Kersa district of Eastern Hararghe, Oromia, Ethiopia also shows that a low household wealth index was significantly associated with underfive children’s mortality OR 1.26 (1.10, 1.43) [27].
2.2.1. 3. Household size
Children born in households with at least 6 members experienced lower mortality rates. The likelihood of mortality was 66% lower (95% CI: 0.21–0.55) among children born in households with > 5 members than among those born in households with fewer than 6 members [22]. The possible influence of the interaction between household size and other variables (wealth index, mother’s working status, mother’s education level, and place of residence) on UFM was found to be not significant and is thus not reported. All variance inflation factors (VIFs) were < 10, suggesting that multicollinearity was not a concern in the regression analysis [22]. A study in an Ethiopian Somali regional state suggested that family size was a significant determinant of underfive mortality in the region [19]. According to the EDHS 2011 data analysis, the mortality risk of children increases as the size of the family increases in the region. The risk of dying for a child born in a family of size 4-6 is 1.879 times higher than that for a child born in a family of size 1-3 (reference category). Children born in a family with a size of seven and above have a significantly higher hazard rate than children born in a family with a size of 1-3, i.e., children born in a family of size seven and above have a 2.164 (HR=2.164, 95% CI: 1.987, 8.215) times higher risk of death than children in the reference category [19].
2.2.1. 4. Occupation of mother
The employment status of mothers and husbands was identified as a significantly associated factor with underfive deaths (P value < 0.05). The odds of underfive mortalities were 18.4% (OR=0.816, 95% CI: .666. 999) lower among women who were to work at all compared to those who were skilled or manual workers. The probability of child mortality, under five, was 32% (OR=0.679, 95% CI: .533 .864) and less likely to occur among women with an unemployed husband and 22% (OR=.783, 95% CI: .618 .991) less likely to occur among women whose husbands were professionally employed compared with those who were working as sales and others [14].
2.2.1. 5. Availability of electricity
The likelihood of UFM was also significantly higher among children born in households without electricity, in the eastern and central regions, and those living in rural areas [22]. The odds of UFM were significantly higher among children born in households without electricity (AOR = 1.81, p = 0.026) and those born in the central (AOR = 1.72, p = 0.025) and eastern (AOR = 2.09, p < 0.001) regions [22].
2.2.2. Health-related Factors
2.2.2.1. Maternal TT immunization
Multivariable analyses revealed that the most common factor associated with mortality across all age subgroups was nonuse of tetanus toxoid (TT) vaccinations during pregnancy (aHR 2.28, 95% CI 1.68, 3.09 for neonatal; aHR 1.86, 95% CI 1.24, 2.79 for postneonatal; aHR 2.44, 95% CI 1.89, 3.15 for the infant; aHR 2.93, 95% CI 1.51, 5.69 for the child; and aHR 2.39, 95% CI 1.89, 3.01 for underfive mortality) [18].
2.2.2.2. Contraceptive use
Multivariable analyses revealed that nonuse of contraceptives among mothers was the most common factor associated with mortality across all age subgroups (aHR 1.69, 95% CI 1.21, 2.37 for neonatal; aHR 2.69, 95% CI 1.67, 4.32 for postneonatal; aHR 2.01, 95% CI 1.53, 2.64 for the infant; aHR 2.47, 95% CI 1.30, 4.71 for the child; and aHR 2.03, 95% CI 1.57, 2.62 for underfive mortality) [18].
2.2.2.3. Place of delivery
Nigeria observed that high stillbirth and early neonatal mortality rates have long been associated with unattended deliveries compared with hospital-based deliveries [26]. Evidence from Ethiopian Demographic and Health Survey, 2016 showed that the percentage of underfive mortalities is higher among home deliveries, which is approximately 27.6% compared to 24.7% among health facility deliveries [14]. Evidence from the Kersa HDSS in the Kersa district of Eastern Hararghe, Oromia, Ethiopia also suggested that place of delivery was significantly associated with underfive children’s mortality (OR 1.26 (1.10, 1.43) 1.016 (1.013, 1.12)) [27].
2.2.2.4. Colostrum feeding
Colostrum feeding practice after birth was associated with UFM, whereas the rest of the health-related variables were not found to be significant (COR =2.26, p = 0.042) [22]. According to a study conducted in the Afambo district of Afar Regional State, the chi-square test showed that colostrum feeding was significantly associated (p =0.035, p =0.006 and p =0.001) with the three indicators of child undernutrition (stunting, wasting and underweight) [28].
2.2.3. Biodemographic Factors
2.2.3.1. Mother’s age
Mother’s age was the key factor associated with UFM in Bhutan [22]. Multivariate analysis showed that having >1 under5 child deaths was associated with maternal age at delivery (<18 or >35) of mothers in a study conducted in Iran [29]. Compared to those born to younger (≤25 years) mothers, children born to mothers aged 36–40 years, 41–45 years, and more than 45 years had significantly lower odds of UFM [22]. Children born from mothers whose age is less than or equal to 24 have a significantly lower risk of underfive mortalities (OR=0.295, 95% CI:.227.383) than those born from mothers whose age is between 45 and 49 in Ethiopia [14].
2.2.3.2. Mother’s age at first marriage
The U5MR was found to be higher among children whose mothers were older than 45 years and who were younger than 16 years when they first married [22].
2.2.3.3. Mother’s age at first birth
Maternal age at first birth was identified as a strong predictor of underfive mortalities in both bivariate and multivariate analyses after controlling for the effects of other covariates [14]. A systematic review revealed that a mother’s age at first birth is negatively correlated with infant mortality (IM) in Ethiopia. Its effect (except for children born to mothers older than 20 years of age at first birth) has a significant impact on CM [25]. Similarly, the age of the mother at first birth was significantly associated with underfive mortalities in Ethiopia (P value < 0.0001). The risk of underfive mortality was approximately 55.6% higher for births to mothers giving birth at an earlier age of 11 to 17 years compared with births to mothers 25 and older (OR=1.556, 95% CI: 1.243, 1.949) [14].
2.2.3.4. Sex of the child
In Bangladesh, the present analysis examined underfive mortality, in which neonatal deaths formed the major part due to a rapid decline in childhood mortality during ages 1–4 years of life, and the higher underfive mortality for males than females was due to lower female mortality during the neonatal period [20]. The underfive mortality rate steadily declined over the years from 128/1000 in 1994 to 48 in 2014, and females had 8% lower mortality rates than males [20]. The U5MR was found to be higher among male children in Bhutan. Boys were 1.38 times more likely to die than girls (p = 0.055) [22]. The odds of underfive deaths were also higher for male children (AOR=1.30, CI= [1.07, 1.57], P<0.008) than females in Ethiopia [23].
2.2.3.5. Number of births
Several children is also another significant factor identified in the analysis; it was revealed that ever-experienced complications may likely increase with the number of children, an interesting finding in this study, particularly with low contraceptive use [26]. Children born to mothers who gave birth to more than 2 children had significantly higher odds of dying. The odds of death among children born to mothers who gave birth to 3–4 or more than 4 children were significantly higher than those born to mothers with less than 3 children [22]. The U5MR was found to be higher among children whose mothers had more than 4 births in Bhutan [22].
2.2.3.6. Previous death of a child
Multivariable analyses revealed that one of the most common factors associated with mortality across all age subgroups was mothers who reported previous death of a child [adjusted hazard ratio (aHR) 17.33, 95% confidence interval (CI) 11.44, 26.26 for neonatal; aHR 13.05, 95% CI 7.19, 23.67 for postneonatal; aHR 15.90, 95% CI 11.38, 22.22 for the infant; aHR 16.98, 95% CI 6.19, 46.58 for the child; and aHR 15.97, 95% CI 11.64, 21.92 for underfive mortality [18].
2.2.3.7. Birth order
An increase in children’s birth orders showed a tremendous negative impact on IM in both 2000 and 2005 EDHSs; in particular, the 2nd and 3rd birth orders were dominant determinants. The estimated hazard ratios of mortality were higher for first birth orders than for second and third birth orders [25]. The study results in Ethiopia indicate that the hazard ratio of children who had a birth order of fifth and above was 1.683 [95% CI: 1.190, 2.380]. This means that children born at the fifth and above orders were 1.683 times more likely to die than children born at the 1st - 2nd order [17]. A study in an Ethiopian Somali regional state also suggested that birth order was a significant determinant of underfive mortality in the region [19]. According to this study, higher birth orders (>4) have the highest mortality risk. Children with these characteristics are 2.067 times more likely to die in age less than 5 relative to the reference group births of order one (HR=2.067, 95% CI: 1.098 to 8.256). Children of order two through four are dying at a rate 23.6% higher than a child of order one (HR=1.236, 95% CI: 1.031 to 12.199). The confidence intervals for higher birth order and birth order two through four indicate that the rate could actually be as high as 8.256 and 12.199 and as low as 1.098 and 1.031, respectively [19].
2.2.4. Environmental Factors
2.2.4.1. Safe drinking water
A study in an Ethiopian Somali regional state suggested that the source of drinking water was a significant determinant of underfive mortality in the region [19]. The risk of dying for a child born in a family without access to pipe drinking water is higher by 76% relative to those born in a family with access to pipe drinking water. The 95% confidence interval (1.421, 9.373) implies that the risk of death of children whose source of water is not pipe water is 1.421 as low and 9.373 as high as those in the reference group [19].
2.2.4.2. Safe sanitation facilities
The likelihood of UFM was 1.49 times higher for those children born in households without safe sanitation facilities than their counterparts (p = 0.012) [22].
2.2.4.3. Solid fuel use
Furthermore, the U5MR was significantly higher among children born in households that used solid fuel. The likelihood of UFM was 2.18 and 1.95 times significantly higher among children born in households without safe sanitation and those that used solid fuel for cooking, respectively [22].
2.3. Conceptual Framework