Cognitive outcomes of children born extremely or very preterm since the 1990s and associated risk factors: A meta-analysis and meta-regression

Abstract

IMPORTANCE: Despite apparent progress in perinatal care, children born extremely or very preterm (EP/VP) remain at high risk for cognitive deficits. Insight into factors contributing to cognitive outcome is key to improve outcomes after EP/VP birth. OBJECTIVE: To examine the cognitive abilities of children of EP/VP birth (EP/VP children) and the role of perinatal and demographic risk factors. DATA SOURCES: PubMed, Web of Science, and PsycINFO were searched without language restriction (last search March 2, 2017). Key search terms included preterm, low birth weight, and intelligence. STUDY SELECTION: Peer-reviewed studies reporting intelligence scores of EP/VP children (<32 weeks of gestation) and full-term controls at age 5 years or older, born in the antenatal corticosteroids and surfactant era, were included. A total of 268 studies met selection criteria, of which 71 covered unique cohorts. DATA EXTRACTION AND SYNTHESIS MOOSE: guidelines were followed. Data were independently extracted by 2 researchers. Standardized mean differences in intelligence per study were pooled using random-effects meta-analysis. Heterogeneity in effect size across studies was studied using multivariate, random-effects meta-regression analysis. MAIN OUTCOMES AND MEASURES: Primary outcome was intelligence. Covariates included gestational age, birth weight, birth year, age at assessment, sex, race/ethnicity, socioeconomic status, small for gestational age, intraventricular hemorrhage, periventricular leukomalacia, bronchopulmonary dysplasia (BPD), necrotizing enterocolitis, sepsis, and postnatal corticosteroid use. RESULTS: The 71 included studies comprised 7752 EP/VP children and 5155 controls. Median gestational age was 28.5 weeks (interquartile range [IQR], 2.4 weeks) and the mean age at assessment ranged from 5.0 to 20.1 years. The median proportion of males was 50.0% (IQR, 8.7%). Preterm children had a 0.86-SD lower IQ compared with controls (95% CI, -0.94 to - 0.78, P