ABSTRACT: A proactive approach to the care of extremely preterm infants has increased survival and lowered the gestational age of viability, but these improvements may be associated with later neurodevelopmental disability. EXPRESS is a national population-based prospective study of all infants born alive or stillborn at less than 27 weeks’ gestation between 2004 and 2007 in Sweden. This prospective follow-up study was undertaken to assess neurologic and developmental outcome of the EXPRESS cohort at 2.5 years corrected age compared with a matched control group born at term.
Of 707 live-born infants, 497 (70%) survived to corrected age 2.5 years; the final cohort included 491 children. Each preterm child was matched with 2 control subjects at 2.5 years chronological age. Cognitive, language, and motor development were assessed with the Bayley Scales of Infant and Toddler Development (Bayley III). Cerebral palsy (CP), visual and hearing disability, and a composite outcome of overall disabilities were assessed. The overall outcome was characterized as no, mild, moderate, and severe disability.
Of 415 infants assessed with clinical examinations, 399, 393, and 382, respectively, completed the Bayley III cognitive, language, and motor scales; 366 control children were assessed with Bayley III. The mean composite cognitive, language, and motor scores for children in the preterm and control groups were 94 ± 12 and 104 ± 11, respectively (P < 0.001), 98 ± 17 and 109 ± 12 (P < 0.001), respectively, and 94 ± 16 and 107 ± 14 (P < 0.001), respectively. Normal cognitive development or mild cognitive disability was found in 354 preterm children (88.8%) and 364 control children (99.5%). Moderate or severe cognitive disability was present in 20 preterm children (5.0%) and 1 control child (0.3%) (P < 0.001) and in 25 (6.3%) and 1 (0.3%), respectively (P < 0.001). Normal language development or mild language disability was found in 330 children (83.9%) in the preterm group and with 351 (97.5%) in the control group (all group comparisons, P < 0.001). Normal motor development or mild motor disability occurred in 324 (84.8%) and 348 (98.6%) of children in the preterm and control groups, respectively. Moderate or severe mental developmental delay was seen in 88 and 10 children (20% and 2.8%), respectively (P < 0.001).
In the preterm group, Bayley III cognitive, language, and motor scores increased with advancing gestational age at birth by 2.5 points (99% confidence interval [CI], 1.0–4.0) per week (P < 0.001), by 3.6 points (99% CI, 1.6–5.6) per week (P < 0.001), and by 2.5 points (99% CI, 0.5–4.5) per week scores (P = 0.001), respectively. Cerebral palsy was present in 32 preterm children (7.0%; 99% CI, 3.9–10.1%). Of 456 preterm children, 42.1% were classified as normal, 30.7% as having mild disabilities, and 27.2% as having moderate or severe disabilities (vs 78.1%, 18.6%, 3.3% of control subjects, respectively; P < 0.001 for all comparisons). The proportion of children with mild or no disabilities increased from 40% at 22 weeks to 83% at 26 weeks (P < 0.001 for trend). Moderate or severe disabilities decreased from 60% at 22 weeks to 17% at 26 weeks (P < 0.001 for trend).
The impact of prematurity on neurodevelopmental outcome indicates that further improvements in neonatal care are necessary. Although preterm children had poorer neurodevelopmental outcomes than those born at term, 73% had no or mild disability, and neurodevelopmental outcome improved with each week of gestational age. These results are relevant for clinicians counseling couples facing extremely preterm birth of their infant.