Outcomes in extremely premature infants: a comparison of 2 regional cohorts born 20 years apart

It is widely accepted that antenatal steroid therapy and surfactant administration have largely contributed to improve the survival of extremely preterm infants. However, few data are available to detail the impact of the introduction of these therapeutic strategies on the characteristics of preterm populations and on the subsequent outcomes of these infants. Moreover, most studies comparing the outcomes of preterm populations over time come from tertiary referral centers rather than geographic regions and therefore they may be biased by changes in referral patterns (eg, omission of healthier infants who are not referred).
An American group has reported perinatal characteristics, neonatal morbidities, and early neurodevelopmental outcomes of a geographically defined populations of infants born at <30 weeks' gestational age cared for at the same regional center from 1985 to 1986 (cohort 1) and from 2005 to 2006 (cohort 2).
Sociodemographically matched term controls were recruited for each cohort. The two groups were compared in terms of perinatal characteristics, mortality rates, and survival with and without impairments at 24 months' corrected age.
Overall, there was a 35% increase in the number of live-born preterm births (138 in cohort 1 and 187 in cohort 2) despite a >10% decline in total births in the region (p<0.001). Survival to hospital discharge increased from 82% to 93% (p<0.002); this increase can be mostly attributed to higher survival for infants born at <27 weeks' gestation (63% vs 88%; p<0.004). Changes in management in cohort 2 with respect to cohort 1 included the use of surfactant (62% of infants) and increased use of postnatal steroids (39% vs 9%, respectively; p<0.001). These treatments significantly shortened the median duration of mechanical ventilation (13 vs 21 days, respectively; p<0.001); however, the incidence of bronchopulmonary dysplasia was higher in cohort 2 (56% vs 35%; p<0.001). A significant decrease in the incidence of severe ultrasound abnormalities was also observed in cohort 2 (from 17% to 7%; p<0.008). At 24 months of age, 7% of cohort 1 and 5% of cohort 2 had an abnormal neurologic exam; Bayley cognitive scores were improved in cohort 2 (significantly closer to the mean of their controls). As a result, survival without severe neurodevelopmental impairment significantly increased from 62% in cohort 1 to 81% in cohort 2 (p<0.001).
Taken together, these data provide information concerning severe neurodevelopmental impairments in former extremely preterm infants at 2 years of age. Even if the predictive validity of developmental testing at 2 years for cognitive function at school age is poor, it may be preliminary concluded that there has been a significant increase in live births at <30 weeks' gestational age, with a greater percentage of these neonates surviving without severe neurodevelopmental impairment at 24 months. Further studies with a school-age follow-up are required to confirm these findings.

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