Global prevalence of neonatal mortality in preterm infants: a systematic review and meta-analysis

The leading cause of neonatal mortality is preterm birth, with the risk of death in the first days of life increasing as the gestational age decreases. The objective was to estimates the global prevalence of neonatal mortality in preterms through a systematic review and meta-analysis of cohort studies. Observational cohort studies were included irrespective of temporal or linguistic confines. Studies reporting the prevalence of newborns delivered before 37 complete weeks of gestation, with deaths within 28 days postpartum, were included. The bibliographic search and selection were conducted across multiple databases, including PubMed/Medline, SciVerse Scopus, Web of Science, CINAHL Information Systems, Scientific Electronic Library Online, EMBASE, Latin American and Caribbean Health Sciences Literature and gray literature. Quality assessment was carried out using the Joanna Briggs Institute appraisal tool. Meta-analysis was conducted utilizing RStudio software. A total of 47 articles were included. Of them, 29 studies analyzed general preterm birth (delivery before 37 complete weeks of gestation), three studies evaluated extremely preterm (< 28 weeks), seven studies assessed very preterm (28 to less than 32 weeks), and five studies examined moderate to late preterm infants (32 to 37 weeks). The pooled prevalence of neonatal mortality was 8%. When considering only the subgroup of general preterm, the mortality rate was 10%. Extremely preterm infants had a mortality rate of 40%, very preterm infants had a rate of 15%, and moderate to late preterm infants had a mortality rate close to 0%. High heterogeneity was found (I² = 100%; Q-test p = 0; wide prediction interval). Meta-regression analyses were conducted to examine the observed heterogeneity. Factors such as Human Development Index and admission to NICUs influenced neonatal mortality. In terms of quality assessment, 89.1% of the studies were considered adequate in representing the target population. Regarding sample size, 30.4% of studies lacked calculations, hindering evaluation. The prevalence of neonatal mortality was 8 per 100 premature births. The prevalence of neonatal mortality varied according to gestational age at birth. These data should be interpreted with caution as it was not possible to identify all sources of heterogeneity in the meta-analysis.