Neuropsychological Functioning in Preterm-Born Twins and Singletons at Preschool Age.

OBJECTIVES: A limited body of research is available on the relationships between multiplicity of birth and neuropsychological functioning in preterm children who were conceived in the age of assisted reproductive technology and served by the modern neonatal intensive care unit. Our chief objective was to evaluate whether, after adjustment for sociodemographic factors and perinatal complications, twin birth accounted for a unique portion of developmental outcome variance in children born at-risk in the surfactant era. METHODS: We compared the neuropsychological functioning of 77 twins and 144 singletons born preterm (<34 gestational weeks) and served by William Beaumont Hospital, Royal Oak, MI. Children were evaluated at preschool age, using standardized tests of memory, language, perceptual, and motor abilities. RESULTS: Multiple regression analyses, adjusting for sociodemographic and perinatal variables, revealed no differences on memory or motor indices between preterm twins and their singleton counterparts. In contrast, performance of language and visual processing tasks was significantly lower in twins despite reduced perinatal risk in comparison to singletons. Effect sizes ranged from .33 to .38 standard deviations for global language and visual processing ability indices, respectively. No significant group by sex interactions were observed, and comparison of first-, or second-born twins with singletons yielded medium effect sizes (Cohen's d=.56 and .40, respectively). CONCLUSIONS: The modest twin disadvantage on language and visual processing tasks at preschool-age could not be readily attributable to socioeconomic or perinatal variables. The possibility of biological or social twinning-related phenomena as mechanisms underlying the observed performance gaps are discussed. (JINS, 2016, 22, 865-877).

Physical growth in the neonatal intensive-care unit and neuropsychological performance at preschool age in very preterm-born singletons.

We studied the associations between early postnatal growth gains and neuropsychological outcome in very preterm-born children. Specifically, we wished to establish whether relationships exist between gains in head circumference (relative to gains in body-weight or length), from birth to hospital discharge, and intellectual, language, or motor, performance at preschool age. We used data from 127 preschoolers, born <33 weeks, all graduates of the William Beaumont Hospital Neonatal Intensive-Care Unit (NICU) in Royal Oak, MI. Cognitive, motor, and language outcomes were evaluated using the Wechsler Preschool and Primary Scales of Intelligence-Revised, Peabody Developmental Scales - 2(nd) Edition, and the Preschool Language Scale - 3(rd) Edition, respectively. Differences between Z-scores at birth and hospital discharge, calculated for three anthropometric measures (head circumference, weight, length), were variables of interest in separate simultaneous multiple regression procedures. We statistically adjusted for sex, socioeconomic status, birth weight, length of hospitalization, perinatal complications, and intrauterine growth. Examination of the relationships between anthropometric indices and outcome measures revealed a significant association between NICU head growth and global intelligence, with the Z-difference score for head circumference accounting for a unique portion of the variance in global intelligence (ηp(2) =.04). Early postnatal head growth is significantly associated with neuropsychological outcome in very preterm-born preschoolers. To conclude, despite its relative brevity, NICU stay, often overlapping with the end of 2(nd) and with the 3(rd) trimester of pregnancy, appears to be a sensitive developmental period for brain substrates underlying neuropsychological functions.

Cumulative Antenatal Risk and Kindergarten Readiness in Preterm-Born Preschoolers.

A suboptimal intrauterine environment is thought to increase the probability of deviation from the typical neurodevelopmental trajectory, potentially contributing to the etiology of learning disorders. Yet the cumulative influence of individual antenatal risk factors on emergent learning skills has not been sufficiently examined. We sought to determine whether antenatal complications, in aggregate, are a source of variability in preschoolers' kindergarten readiness, and whether specific classes of antenatal risk play a prominent role. We recruited 160 preschoolers (85 girls; ages 3-4 years), born ≤336/7 weeks' gestation, and reviewed their hospitalization records. Kindergarten readiness skills were assessed with standardized intellectual, oral-language, prewriting, and prenumeracy tasks. Cumulative antenatal risk was operationalized as the sum of complications identified out of nine common risks. These were also grouped into four classes in follow-up analyses: complications associated with intra-amniotic infection, placental insufficiency, endocrine dysfunction, and uteroplacental bleeding. Linear mixed model analyses, adjusting for sociodemographic and medical background characteristics (socioeconomic status, sex, gestational age, and sum of perinatal complications) revealed an inverse relationship between the sum of antenatal complications and performance in three domains: intelligence, language, and prenumeracy (p = 0.003, 0.002, 0.005, respectively). Each of the four classes of antenatal risk accounted for little variance, yet together they explained 10.5%, 9.8%, and 8.4% of the variance in the cognitive, literacy, and numeracy readiness domains, respectively. We conclude that an increase in the co-occurrence of antenatal complications is moderately linked to poorer kindergarten readiness skills even after statistical adjustment for perinatal risk.

Postnatal growth and neuropsychological performance in preterm-birth preschoolers.

OBJECTIVE: Compromised postnatal growth is an important risk factor accounting for poorer neuropsychological performance of preterm children during the preschool years, yet its unique contribution to explaining outcome variance within this high risk group has yet to be determined. Therefore, we examined within a large preterm sample (1) the relationships between head growth, measured either at birth or preschool age, and outcome; (2) the relationships of binary versus dimensional head growth measures and performance; and (3) the unique contribution of preschool-age head growth, after adjustment for general physical development (indexed by stature), to variance in neuropsychological functioning. METHOD: We evaluated 264 preterm (<36 weeks) preschoolers, without severe handicaps, using cognitive, language, and motor skill measures. Multiple regression analyses, adjusting for sociodemographic factors and pre-, peri-, and postnatal confounds, were used to study associations between growth indices and performance. RESULTS: While suboptimal head growth classification at birth was significantly associated only with motor performance, suboptimal head growth at preschool age explained a significant portion of variance in intellectual and language measures (g = .46 to .60). Treating preschool head size as a continuous dimension yielded null results, however, with body-height explaining a significant portion of the variance across several domains. CONCLUSION: Among postnatal anthropometric indices, preschool stature, rather than head circumference, remains a consistent correlate of preschool outcome in preterm children, highlighting the contribution of general physical development to neuropsychological performance. Further investigation of the underlying mechanisms likely involves exploration of complex relationships between postnatal nutrition, growth hormone levels, body and brain development, and neuropsychological functioning.