In this review, the pooled neonatal mortality rate was 19.0% which is higher among early age and preterm newborns than their counterparts. Early age of the newborn, prematurity, low birth weight, perinatal asphyxia, mode of delivery, hypothermia, late initiation of breastfeeding, and having antenatal care visits were the main determinants for neonatal mortality among neonates admitted to intensive care units.
Previous literature indicated that the overall mortality rate in NICU of developing countries ranged from 0.2–64.4% [34]. In our systematic review and meta-analysis, using the random effect model, the pooled neonatal mortality rate was estimated to be 19% (95% CI: 15.0–23.0%) which is higher than the pooled estimate of neonatal mortality at NICU of Iran (11.40%) [35]. However, previously in Brazil, a wide variation in the mortality rates was found among intensive care units (9.5–48.1%), with an overall mortality rate for newborns admitted at nine NICU sites being 18.6% [36] which is comparable to our result. It is also indicated that neonatal mortality rate varies significantly between the central and western parts of Iran [35]. This is comparable to our subgroup analysis that showed a significantly higher NMR in Oromia region than other regions. This variation might be related to the difference in availability of equipment type, and severity of disease in admitted neonates, as well as the performance of physicians, midwifes and neonatal nurses in different regions of Ethiopia. Moreover, the regional variation would be associated with suboptimal NICU neonatal services across the country [24, 30].
Our stratified analysis also showed that preterm neonates had three times higher odds of death as compared to preterm and term and post-term neonates. A recently conducted individual study conducted in Ethiopia indicated that the odds of neonatal mortalities among preterm neonates were 2.2 times higher than that of term neonates [37]. A systematic review and meta-analysis result showed that neonatal mortality was the lowest in the full-term newborn infants but higher among neonates with a gestational age of 28–32 weeks [38]. The most common causes of mortality in NICUs of Iran were prematurity (44.14%) [35]. This could be also supported by the previous study as preterm birth (40.8%) and intrapartum complications (27.0%) accounted for most early neonatal deaths [39]. This is due to the fact that preterm newborn had immaturity of immune systems and other body defense mechanisms which help to control newborn infection and disease susceptibility. Other possible explanations for the high death rate of preterm neonates might be due to delay in receiving adequate health care due to poor facilities and lack of medical supplies in Ethiopia.
In this review, gestational age or prematurity was related to as a factor to neonatal mortality. The finding is also consistent with the systematic review in developing and developed countries [34]. It might be due to their intrinsic susceptibility to infection due to lack of immunologic competence, the lack of appropriate treatment modalities, such as mechanical ventilation, surfactant administration, parenteral nutrition and delay in the initiation of health care services [27, 33].
Perinatal asphyxia is identified as a risk factor for neonatal mortality. The reason might be the quality and access of emergency obstetric newborns and comprehensive emergency obstetric services are inadequate in a clinical setting [25, 27]. Training of health care workers to detect risk factors, fetal asphyxia during labor and delivery including provision of neonatal resuscitation must be given [33].
We observed that mode of delivery showed a variation in the rate of neonatal mortality. Instrumental mode of delivery is also identified as a risk factor for neonatal mortality [30]. It gives a clue as there is fetus suffocation, early rupture of membrane and environmental contamination with nosocomial infections during delivery [26]. On the other hand, it is also reported that cesarean mode of delivery had a protective effect on the risk of neonatal mortality [25]. This finding is consistent with the study done in Brazil [36]. It might be related to the use of timely decisions rather than waiting for vaginal delivery. Delivering by cesarean section reduces the risk of death and complications that can come due to prolonged labor [25]. On the contrary, it is reported that the cesarean section had increased neonatal mortality which could have resulted from the delay in decision making during prolonged labor, poor quality of operation procedure and its prohibition effect on early breastfeeding initiation [30, 25, 32].
Delayed breastfeeding after 1 hour of birth results in a higher risk of neonatal mortality compared to their counterpart [25, 31]. This indicates the sub-optimal practice of early initiation of breastfeeding despite its great importance in the reduction of neonate death. It is also important to consider the neonates who are sick that might not be able to suck breast milk as compared to a healthier one [25].
Neonates born from mothers who had no ANC visit are more likely to die compared to neonates born from mothers who have ANC follow up [30, 26, 25, 31]. ANC visit saves the lives of babies by early detection and management of the problems related to the pregnancy by promoting and establishing good health [25, 31].
The current systematic review and meta-analysis are the first of its kind to be conducted at the NICU hospitals of Ethiopia to assess the burden and determinant factors associated with neonatal mortality in Ethiopia. The information obtained may improve knowledge on the cause of neonatal mortality at NICU so as to reduce neonatal mortality rates in Ethiopia. But the inclusion of only English language articles in the review is a limitation. Moreover, all the studies are based on facility-based records that are subject to information bias.