Perinatal asphyxia and its associated factors in Ethiopia: a systematic review and meta-analysis

Perinatal asphyxia is the failure of neonates to initiate and sustain breathing at birth which causes significant neonatal morbidity and mortality to the extent of the first week of life [1]. Perinatal asphyxia is a condition that occurs when there is an impairment of blood gas exchange that results in hypoxemia and hypercapnia. Moreover, perinatal asphyxia requires adequate and quick resuscitation measures [2, 3]. The combination of hypoxia and ischemia will result in a cascade of biochemical changes in the body leading to brain neuronal death and brain damage during the antepartum or intrapartum period [4].

According to the World Health Organization (WHO), there were nearly four to nine million newborns develop birth asphyxia each year. APGAR score is used to determine the level of perinatal asphyxia, evaluated in the 1st and 5thminutes of life with scores ranging from zero to ten. Four to seven APGAR score in the first minute of life indicates moderate perinatal asphyxia and between zero and three indicates severe asphyxia [5].

According to WHO, perinatal asphyxia is characterized by profound metabolic acidosis, PH < 7.20 on umbilical cord arterial blood sample, the persistence of an APGAR score of 3 at the 5th minute, clinical neurologic sequelae in the immediate neonatal period, evidence of multi-organ system dysfunction (brain damage, heart, lungs, gut, kidneys) in the immediate neonatal period. Pre-pregnancy risk factors for perinatal asphyxia are; maternal age ≥ 35 years, social factors, family history of neurologic disease, infertility treatment, previous neonatal death, chronic illness. Whereas antepartum risk factors include; maternal thyroid disease, severe preeclampsia, multiple gestation, chromosomal/genetic abnormalities, congenital malformations, intrauterine growth restriction, trauma, malpresentation, and antepartum hemorrhage. Besides, chorioamnionitis, meconium-stained amniotic fluid, operative vaginal delivery, general anesthesia, emergency cesarean delivery, placental abruption, cord accident, uterine rupture, maternal cardiac arrest, and fetal exsanguinations were the intrapartum risk factors for perinatal asphyxia [3, 6].

In low and middle-income countries neonatal mortality rate constitutes 42% of under-5 deaths [1, 6, 7]. According to the World Health Organization report, perinatal asphyxia is the third leading cause of under-5 child deaths (11%) following preterm birth (17%) and pneumonia (15%) [2, 6, 8]. In low and middle-income countries, neonatal deaths accounted for 52% of all under-5 child mortality in South Asia, 53% in Latin America and Caribbean, and 34% in Sub-Saharan Africa due to preventable causes including perinatal asphyxia [9].

Aslam HMSS et. al [3] in Ethiopia, perinatal asphyxia is one of the leading causes of neonatal mortality, which accounts for 34% [10]. Therefore, this systematic review and meta-analysis aimed to estimate the pooled prevalence of perinatal asphyxia and to identify the determinant factors in Ethiopia.

According to the results of this meta-analysis, the pooled prevalence of perinatal asphyxia in Ethiopia was estimated to be 24.06% (95% CI: 18.11, 30.01). Practicing standard guidelines during labor and delivery across different hospitals and health institutions could reduce this significant neonatal burden at the national level.

This study finding is in line with the study done in Nigeria reporting that, 30.1% [20] and Tanzania (21.1%) [21] of the neonates were having perinatal asphyxia. The finding of this study is lower than the study conducted in Bangladesh which was estimated 56.9% [22]. The discrepancy might be due to the difference of good utilization of different intrapartum fetal monitoring equipment and tools, having qualified professional and quality of care given services to neonates in Ethiopia.

The finding of this systematic review is higher than the study conducted in Thailand, Malawi and Guinea accounted for 11.7% [23], 6.1% [24] and 2.4% [25] respectively. This discrepancy might be due to socio-cultural, antenatal care service accessibility, and variability in maternal risk factor distribution. Besides, most of the studies included in this meta-analysis were conducted in hospitals and health centers which might increase the prevalence.

Neonates born with low birth weight were 6.52 times (OR: 6.52, 95% CI: 4.40, 9.65) more likely to develop birth asphyxia as compared to neonates born with normal birth weight. Similar study findings were observed in different countries: Uganda [26], Indonesia [27], Pakistan [3], East Java [28] and Thailand [29]. This could be explained by because a high proportion of small babies might be pre-term that they might not have enough surfactant which might not prevent suffering from difficulty of breathing and developing difficulty in cardiopulmonary transition and subsequent birth asphyxia.

The likelihood of developing birth asphyxia among neonates born with meconium-stained amniotic fluid was 5.91 times (OR = 5.91, 95% CI: 3.95, 8.83) as likely to have birth asphyxia as those born with clear amniotic. This finding was consistent with the study conducted in India [30, 31] in Iraq [32], and Uganda [26]. The possible reason could be because the intrapartum inhalation of meconium-stained amniotic fluid resulted in chemical pneumonitis with inflammation of the pulmonary tissues, mechanical obstruction of airways, and pulmonary air leak, inducing hypoxia [33].

Newborns delivered with assisted instrumental deliveries 4.04 times (OR = 4.04, 95%CI = 2.48, 6.60) more likely to develop perinatal asphyxia as compared to with neonates delivered spontaneously. This study finding is supported by the study done in India [30] and Iran [34]. The possible explanation for this might be because instrumental delivery causing birth trauma leads to asphyxia. Instrumental deliveries may affect different locations of cranial hemorrhage; subdural, subarachnoid, intra-parenchyma or intra-ventricular due to exerting pressure of a vacuum and forceps extractors can cause brain bleeds on the cranium contributing to intracranial hemorrhage resulting birth asphyxia, bleeding diathesis, infection, and vascular anomalies. As evidenced by a piece of literature, the incidence of traumatic intracranial hemorrhage of six per 1000 live neonates born than spontaneously had born [35].

The odds of birth asphyxia among babies born to mothers with prolonged labor were about 2.79 times (OR = 2.79, 95%CI = 1.98, 3.93) higher than their counterparts. The finding of this study is consistent with the study done in Bangladesh [36], Cameroon [37], Nigeria [20] and Sweden [38]. This could be because if the labor does not progress normally, the laboring mother may experience serious complications, such as dehydration, exhaustion, or rupture of the uterus [39] and if labor becomes prolonged, there is a high chance of the fetus to become distressed.

Despite this, there is a standard guideline for neonatal resuscitation; the death of neonatal mortality is increasing in Ethiopia. In the Ethiopian context with the adoption of the WHO neonatal resuscitation procedures are employed. Initiate cardiac massage at a rate of 120 beats/min, intubation and continuous positive pressure ventilation with 100% of oxygen at a rate of 40 breaths per minute, observe for improvements intermittently (initiation of spontaneous respiration; color, heart rate), administer normal saline and sodium bicarbonate to counter acidosis and shock respectively), and adrenalin through endotracheal tube were the procedures for neonatal resuscitation [40].

This systematic review and meta-analysis had significant heterogeneity which may prone to publication bias. This might be due to the sample size of each study, the nature of the study design, the study setting or region. Despite this review has marked heterogeneity, subgroup analysis was computed using study setting and sample size and showed improvement of marked heterogeneity to a moderate extent, resulting in reducing the having the chance of publication bias.

The overall pooled prevalence of perinatal asphyxia was remarkably higher. Prolonged labor, meconium-stained amniotic fluid, instrumental deliveries, and low birth weight were the determinants factors of perinatal asphyxia in Ethiopia. Therefore, efforts might be made to improve the quality of intrapartum care services to prevent labor, delivery and fetal complications and to identify and make a strict follow up of mothers with meconium-stained amniotic fluid. Addressing and identifying determinants and magnitudes of hypoxic-ischemic encephalopathy may improve the implementation of the WHO standard guideline effectively and consistently.