Survival of very preterm infants in the Islamic Republic of Iran: A population-based retrospective cohort study.

Estimation of the survival of very preterm infants is necessary to make decisions and design interventions in order to improve their quality of care. This survey aimed to estimate the survival of very preterm infants born at 23 up to 33 weeks of gestational age (GA) in Iran. This population-based retrospective cohort study included 8536 infants born before 33 weeks of GA, from March 21st to December 22nd 2013 in Iran. The primary data were extracted from the Iranian national maternal and neonatal registration network (IMAN). All infants who have been discharged alive, followed up by telephone contact up to one year after birth. The Kaplan-Meier and Log-rank tests were performed to estimate survival and to compare survivals, respectively, using SPSS version 26 and R 3.5.2 softwares. The overall survival was estimated at 56.70% (95% C.I: 55.60%-57.80%) at the end of the follow-up period. Total death rate was estimated at 43.30% and was significantly decreased with increasing birth weight (p<0.0001). Survival was increased significantly with increasing GA (p<0.0001), from 5.7% at 23 weeks to 79.6% at 32 weeks. The estimated cumulative proportion of death until the end of the neonatal period had a decreasing trend and then had a steady trend until the end of the follow-up period. The hazard ratio of quadruple or more birth and GA were 1.46 (p=0.021) and 0.83 (p<0.001), respectively. The overall estimated survival of very preterm infants was not high. Even with modern perinatal technology and care, early deaths of very preterm infants were still common.