Page 30 - Sample Moderate prematurity, socioeconomic status, and neurodevelopment in early childhood

Chapter 3
INTRODUCTION
Worldwide the preterm birth rate in 2005 was an estimated 9.6% (12.9 million births).1 The highest rates were in Africa (11.9%) and North America (10.6%) and the lowest rates in Europe (6.2%).1 In the Netherlands 7.7% of children were born preterm in 2008.2 United States data show a rise in the preterm birth rate from 9.4% in 1981 to 12.3% in 2003, with the highest increase in rates of moderately preterm-born children (MP; 32-35 weeks’ gestation).3 The rate of children born very preterm (<32 weeks) remained relatively constant during the same period at 1.8 to 2.0%. In other words, children born after 32 weeks gestation comprise more than 85% of all preterm births.3-5
Accumulating evidence shows that MP children are at greater risk for developmental and health problems than term-born children (38-41 weeks’ gestation). Several follow-up studies have reported that MP children are not only at risk for short-term morbidity and mortality,6-8 but also for numerous developmental and school-related problems in the long-term.9-11
However, evidence concerning long-term behavioural and emotional problems among MP children is limited.12-16 One study on 52 late preterm-born children (born at 34-36 weeks) showed no differences in externalizing, internalizing, aggressive, and anxious/depressed problems compared to term-born children.12 In contrast, Van Baar et al. reported that MP children were more likely to have behavioural and emotional problems at ages 7 to 9, specifically attention and internalizing problems.13 A recent study of Talge et al. confirmed the presence of more attention and internalizing problems in 6-year-old children born at 34-36 weeks’ gestation.14 Furthermore, Gray et al. reported that ~20% of MP children with low birth weight had behavioural problems at 3, 5 and 8 years of age, compared to the expected 10% in normative samples if using the same cut-off.15, 17
Although it is shown that very preterm and low birth weight children have considerably more behavioural and emotional problems,18 large prospective cohort studies on moderately and late preterm-born children are lacking. The few small studies showed conflicting results.12-14 Therefore, the purpose of this study was to determine the occurrence of behavioural and emotional problems, overall and for separate types of problems, in a large cohort of MP pre-school children and to compare the occurrence with term-born controls. Furthermore, we assessed these problems by gender.
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