2.1. Under-five Mortality Rate
An analysis of the Bhutan National Health Survey 2012 showed that Bhutan’s UFM rate was 59 per 1000 live births (Dendup et al., 2018). Evidence from the Nepal Demographic and Health Survey (2001–2016) indicated a U5MR of 104 per 1000 live births (Ghimire et al., 2019). In Ethiopia, it was approximately 67 per 1000 live births from 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 first gave birth respectively (Chaltu et al., 2019).
2.2. Factors Associated with Under-five 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 (Chowdhury et al., 2017). In a study conducted in 2015, the mean years of schooling showed a significant correlation with the decrease of mortality rates meaning as education level increased, 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, and thus reducing the mortality and morbidity in West and South Asian countries (Alimohamadi et al., 2019). 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 (Chowdhury et al., 2017). The U5MR was found to be significantly lower among children born to parents who attended at least a high school education in Bhutan (Dendup et al., 2018). 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 whose household head had received high school education (Dendup et al., 2018).
For instance, in South Africa, falling behind in school was the strongest risk factor for giving birth within the following two years (Glynn et al., 2018). The study results in Nigeria showed that the risk of childhood mortality is 26.7%, 39.7 and 45.9% lower among the mothers having primary, secondary and tertiary education respectively than those with no formal education (Yaya et al., 2017). One of the pathways by which mothers’ education affects child survival is through improved child care (Yohannes et al., 2017). This is probably because those with little education before marriage may be unable or poorly equipped to take appropriate reproductive health decisions that are important in reducing pregnancy-related complications (Adedokun et al., 2017). Increased schooling has been associated with better health of women and their children in Zambia (Sandoy et al., 2016). 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. Also in a Gilgel Gibe field research of determinants of UFM, children born to mothers whose educational level was below elementary were 14 times more likely to die compared to children whose mothers’ education is above elementary (Yohannes et al., 2017). Similarly, evidence from EDHS 2016 data analysis suggests that deaths among under-five children differed significantly with the level of mothers’ education, with those of relatively higher education, having a lower chance of experiencing under-five deaths (P-value < 0.001) (Berhanu, 2019). Children born to a mother with no education at all were associated with a 2.61 times increased risk of under-five 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 at the risk of under-five 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 (Berhanu, 2019). Evidence from Kersa HDSS in Kersa district of Eastern Hararghe, Oromia, Ethiopia also shows that maternal educational status was significantly associated with under-five children’s mortality OR 1.31 (1.13, 1.49) (Melkamu et al., 2015).
2.2.1. 2. Income
Children from low asset category households had on average 1.17 times higher mortality rate than those from high asset category households in Bangladesh (Chowdhury et al., 2017). The odds of UFM reduced significantly with increasing wealth quintiles and were lower among those born to working mothers (Dendup et al., 2018). 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 poorest in Nigeria (Yaya et al., 2017). 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 (Adedokun et al., 2017). Evidence from Kersa HDSS in Kersa district of Eastern Hararghe, Oromia, Ethiopia also shows that low household wealth index was significantly associated with under-five children’s mortality OR 1.26 (1.10, 1.43) (Melkamu et al., 2015).
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 those born in households with less than 6 members (Dendup et al., 2018). The possible influence of 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 (Dendup et al., 2018). A study in an Ethiopian Somali regional state suggested that family size was a significant determinant of under-five mortality in the region (Solomon et al., 2017). 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 family of size 4-6 is higher by 1.879 times relative to those born in family with size of 1-3 (reference category). Children born in a family with the size of seven and above have a significantly higher hazard rate than children born in a family with the 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 as compared with children in the reference category (Solomon et al., 2017).
2.2.1. 4. Occupation of mother
The employment status of mothers and husbands were identified as significantly associated factors with under-five deaths (P-value < 0.05). The odds of under-five mortalities were 18.4% (OR=0.816, 95% CI: .666, .999) lower among women who were to working at all compared to those who were skilled or manual worker. 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 (Berhanu, 2019).
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 (Dendup et al., 2018). 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 (Dendup et al., 2018).
2.2.2. Health-related Factors
2.2.2.1. Maternal TT immunization
Multivariable analyses revealed the most common factor associated with mortality across all age subgroups was nonuse of tetanus toxoids (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 post-neonatal; 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 under-five mortality) (Ghimire et al., 2019).
2.2.2.2. Contraceptive use
Multivariable analyses revealed 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 post-neonatal; 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 under-five mortality) (Ghimire et al., 2019).
2.2.2.3. Place of delivery
Nigeria observed that high stillbirth and early neonatal mortality rate have been long associated with unattended deliveries compared with hospital-based deliveries (Adedokun et al., 2017). Evidence from Ethiopian Demographic and Health Survey, 2016 showed that the percentage of under-five mortalities is higher among home deliveries, which is about 27.6% compared to 24.7% among health facility deliveries (Berhanu, 2019). Evidence from Kersa HDSS in Kersa district of Eastern Hararghe, Oromia, Ethiopia also suggested that place of delivery was significantly associated with under-five children’s mortality OR 1.26 (1.10, 1.43) 1.016 (1.013, 1.12) (Melkamu et al., 2015).
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) (Dendup et al., 2018). According to a study conducted in 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 under-nutrition (stunting, wasting and underweight) respectively (Misgan et al., 2016).
2.2.3. Bio-demographic Factors
2.2.3.1. Mother’s age
Mother’s age was the key factor associated with UFM in Bhutan (Dendup et al., 2018). Multivariate analysis showed that having >1 under-5 child death was associated with maternal age at delivery (<18 or >35) of mothers in a study conducted in Iran (Anafcheh et al., 2018). 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 (Dendup et al., 2018). Children born from mothers whose age less than or equal to 24 have a significantly lower risk of under-five mortalities (OR=0.295, 95% CI: .227,.383) compared to those born from mothers whose age is between 45 and 49 in Ethiopia (Berhanu, 2019).
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, who were younger than 16 years when they first married (Dendup et al., 2018).
2.2.3.3. Mother’s age at first birth
Maternal age at first birth was identified as a strong predictor of under-five mortalities in both bivariate and multivariate analysis after controlling for the effects of other covariates (Berhanu, 2019). A systematic review revealed that a mother’s age at first birth is negatively correlated with infant mortality (IM) in Ethiopia. Its effect (except children born to mothers older than 20 years of age at first births) has a significant impact on CM (Yohannes et al., 2017). Similarly, the age of the mother at first birth was significantly associated with under-five mortalities in Ethiopia (P-value < 0.0001). The risk of under-five mortality was about 55.6% higher for births to mother give birth at earlier age 11 to 17 years compared with births to mothers 25 and higher years old (OR=1.556, 95% CI: 1.243, 1.949) (Berhanu, 2019).
2.2.3.4. Sex of the child
In Bangladesh, the present analysis examined under-five mortality in which the neonatal deaths formed the major part due to rapid decline in childhood mortality during age 1–4 years of life and the higher under-five mortality for male than female was due to lower female mortality during the neonatal period (Chowdhury et al., 2017). The under-five 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 (Chowdhury et al., 2017). 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) (Dendup et al., 2018). The odds of under-five death were also higher for male children (AOR=1.30, CI= [1.07, 1.57], P<0.008) compared to females in Ethiopia (Chaltu et al., 2019).
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 (Adedokun et al., 2017). 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 (Dendup et al., 2018). The U5MR was found to be higher among children whose mothers had more than 4 births in Bhutan (Dendup et al., 2018).
2.2.3.6. Previous death of a child
Multivariable analyses revealed 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 post-neonatal; 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 under-five mortality (Ghimire et al., 2019).
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; particularly the 2nd and 3rd birth order were dominant determinants. The estimated hazard ratios of mortality were higher for first birth orders compared to second and third ones (Yohannes et al., 2017). The study result in Ethiopia indicates hazard ratio of children who had birth order fifth and above was 1.683 [95% CI: 1.190, 2.380]. This means children born at the fifth and above were 1.683 times more likely to die than children born at 1st-2nd order (Dereje et al., 2018). A study in an Ethiopian Somali regional state also suggested that birth order was a significant determinant of under-five mortality in the region (Solomon et al., 2017). 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 (Solomon et al., 2017).
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 under-five mortality in the region (Solomon et al., 2017). 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 (Solomon et al., 2017).
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) (Dendup et al., 2018).
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 (Dendup et al., 2018).
2.3. Conceptual Framework
[See figure 1]