Neurodevelopmental outcome of premature infants born at less than 33 weeks of gestational age and not cerebral palsy at the age of 5 years

To appreciate the impact of prematurity, fetal hypotrophy and familial environment on the neurodevelopmental performances of very premature infants without cerebral palsy at the age of five years. We followed a regional cohort of 171 very premature infants (< or = 32 weeks of gestation) until they were five years of age. Cognitive functions were tested with the WPPSI test and the development quotient was assessed by the ability to draw a "bonhomme". Twenty-two premature infants suffered from cerebral palsy diagnosed before the age of two years. Another infant had a moderate diplegia at the five-year examination. We had no information for 16 prematures (9.3% of survivors). Twenty-eight premature infants were considered as having no severe disability on phone or mailed contact, and another child had a severe isolated mental retardation. We examined 104/148 infants, and 96/148 survivors without cerebral palsy passed the tests. The cognitive functions of these premature infants are compared to the performances of a control group made up of 108 children born at term > or = 37 weeks, matched for birthplace and single or twin characteristics of the pregnancy. The values of the different quotients are significantly decreased in the preterm group. The global IQ and the performance IQ are 0.8 SD, verbal IQ is 0.5 SD and the development quotient is 0.4 SD below the values observed in the control group. A performance IQ less than -2 SD for the mean of the control group is observed three times more than in the controls (13.5% vs 3.7%, P < 0.01). Multiple linear regression shows that prematurity explains, independent of hypotrophy and socioeconomic environment, 8% of the variation of the performance IQ (P < 0.01), 2% of the variation of the verbal IQ and 2% of the development quotient (P < 0.05). The five-year neurologic outcome of the children born prematurely in this regional study is similar to the results observed in regional studies conducted in Europe: 13.4% of the survivors have cerebral palsy, and the cognitive functions of the children with no cerebral palsy are significantly lower than the term control group. Other risk factors such as hypotrophy, which modulates the developmental quotient, and the socioeconomic status, which modulates the verbal IQ, are underlined.