Trends in Gestational Age-Related Intelligence Outcomes of School-Age Children Born Very Preterm from 2001 to 2015 in Taiwan

Abstract

Objective: To investigate whether gestational age (GA)-related intelligence outcomes of children born very preterm improved over time.

Study design: A multicenter cohort study recruited 4717 infants born at GA <31 weeks and admitted to neonatal intensive care units between 2001 and 2015 in Taiwan. Intelligence outcomes at age 5.5 years were classified by intelligent quotient (IQ) into no cognitive impairment (IQ > -1 SD), mild cognitive impairment (IQ = -1∼-2 SD), and moderate/severe cognitive impairment (IQ < -2 SD). Trends were assessed for neonatal morbidities, mortality, and intelligence outcomes by birth epoch (2001-2003, 2004-2006, 2007-2009, 2010-2012, 2013-2015) and GA (23-24, 25-26, 27-28, 29-30 weeks).

Results: Maternal education levels increased and rates of brain injury and mortality decreased over time. Among the 2606 children who received IQ tests, the rates of no, mild, and moderate/severe cognitive impairment were 54.5%, 30.5%, and 15.0%, respectively. There were significant trends in the increasing rates of no cognitive impairment and declining rates of mild and moderate/severe cognitive impairment in all GA groups across the 5 birth epochs. Relative to the occurrence in 2001-2003, the odds were significantly reduced for moderate/severe cognitive impairment from 2007-2009 (aOR 0.49, 95% CI 0.30-0.81) to 2013-2015 (0.35, 0.21-0.56) and for mild cognitive impairment from 2010-2012 (0.54, 0.36-0.79) to 2013-2015 (0.36, 0.24-0.53).

Conclusions: For children born very preterm between 2001 and 2015 in Taiwan, the improvement of maternal education levels and improvements in neonatal brain injury and mortality were temporally associated with trends of decreasing intellectual impairment at school age across all GA groups.

Keywords: IQ; gestational age; preterm children.