[Risk factors among children born at the limit of viability 22+0 - 23+6 weeks].

Despite improved survival of extremely preterm infants born at <28 weeks gestational age (GA) since the 1990s, only few reports on long-term outcomes have been published. The aim of our study was to determine risk factors among mothers and outcomes for their children born at the limit of viability (GA 22 + 0 - 23 + 6 weeks) at the Karolinska university hospital in 2009-19, before and after the introduction of new national interventionist guidelines in 2016. We hypothesized that infant survival, morbidity and cognitive functions at 2 years' corrected age had improved after the new clinical practice. Maternal risk factors were identified, which emphasize the need of standardized follow-up and counseling for women at increased risk of extreme preterm birth. The intrauterine fetal death rates were unchanged. Among births at 22 weeks, the neonatal mortality tended to decrease 96 vs. 76 percent of live births (p = 0,05), and the 2-year survival tended to increase 4 vs 24 percent (p = 0,05). At 23 weeks, the neonatal mortality decreased 56 vs 27 percent of live births (p = 0,01), and the 2-year survival increased 42 vs 64 percent (p = 0,03). In contrast, the morbidity and cognitive disability at 2 years' corrected age were unchanged. Our results were in accordance with previous reports where no substantial improvement in cognitive functions are reported among infants born at GA <24 weeks since the 1990s. They highlight the importance of comprehensive ethical considerations before active interventions at threatening preterm birth < 24 weeks.