Actuarial Survival Based on Gestational Age in Days at Birth for Infants Born at <26 Weeks of Gestation

To provide comprehensive, contemporary information on the actuarial survival of infants born at 22-25 weeks of gestation in Canada.

In a retrospective cohort study, we included data from preterm infants of 22-25 weeks of gestation admitted to neonatal intensive care units participating in the Canadian Neonatal Network between 2010 and 2017. Infants with major congenital anomalies were excluded. We calculated gestational age using in vitro fertilization date, antenatal ultrasound dating, last menstrual period, obstetrical estimate, or neonatal estimate (in that order). Infants were followed until either discharge or death. Each day of gestational age was considered a category except for births at 22 weeks, where the first 4 days were grouped into one category and the last 3 days were grouped into another category. For each day of life, an actuarial survival rate was obtained by calculating how many infants survived to discharge out of those who had survived up to that day.

Of 4335 included infants, 85, 679, 1504, and 2067 were born at 22, 23, 24, and 25 weeks of gestation, respectively. Survival increased from 32% at 22 weeks to 83% at 25^4-6/7 weeks. Graphs of actuarial survival developed for the first 6 weeks after birth in male and female children indicated a steep increase in survival during the first 7-10 days postnatally.

Survival increased steadily with postnatal survival and was dependent on gestational age in days and sex of the child.