Differences in rates and short-term outcomes of very preterm infants in Europe in 2003: the MOSAIC cohort

Very preterm infants constitute approximately one third of deaths in the perinatal period, and survivors are at high risk for long-term disabling impairments. Medical advances in neonatal intensive care coupled with programs to regionalize perinatal care have improved survival after very preterm birth. In some regions, higher survival has been accompanied by increases in short-term morbidity, such as brain haemorrhaging and bronchopulmonary dysplasia. In others, mortality and morbidity both have decreased, so although more infants are at risk, each infant's individual risk for morbidity is lower. Thus, there is no agreement on how improvement in practices and survival may affect rates of impairment. Despite the public health significance of very preterm infants, data for assessing the evolution of their characteristics, mortality, and short-term morbidity are not readily available. There is wide variability in inclusion criteria and completeness in civil and birth registers for very preterm births, and these sources do not often contain information on morbidity. Finally, studies involving preterm infants are hardly comparable due to differences in recruitment criteria.
The Models of Organizing Access to Intensive Care for Very Preterm Births (MOSAIC) study on models of perinatal care and health outcomes of very preterm infants in Europe collected prospective data on all very preterm infants from 10 regions covering half a million total births in 2003. One of the studies' principal aims was to assess the variability in mortality and short-term morbidity in very preterm infants in European regions.
The MOSAIC cohort included 4908 very preterm infants born alive between 24 and 31 weeks of gestation without lethal congenital anomalies.
Results show that live births between 24 and 31 weeks of gestation were 9.9 per 1000 total live births in the MOSAIC regions (range: from 7.6 to 13.0). Standardized mortality was doubled in high versus low mortality regions (18%-20% vs 7%-9%) and differed among regions for infants =28 weeks of gestation as well as 28 to 31 weeks of gestation. Morbidity among survivors also varied (intraventricular hemorrhage (IVH)/periventricular leukomalacia (PVL) ranged from 2.6% to =10% and bronchopulmonary dysplasia (BPD) from 10.5% to 21.5%) but differed from mortality rankings. A total of 85.2 very preterm infants per 10 000 total live births were discharged from the hospital alive with a range from 64.1 to 117.1; the range between regions was 2.1 to 10.2 per 10 000 live births for infants discharged with IVH/PVL and 10.0 to 31.2 for BPD.
Taken together, these findings identified marked differences in very preterm birth rates as well as mortality and short-term morbidity in the 10 population-based cohorts of very preterm infants from regions that participated in the MOSAIC study. This raises questions about variability of treatment and diagnostic practices provided to those infants. Comparative follow-up studies are needed to evaluate the impact of differences in treatment on rates of disabilities associated with preterm births.

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