Elsevier

The Lancet

Volume 369, Issue 9555, 6–12 January 2007, Pages 43-50
The Lancet

Articles
Trends in cerebral palsy among infants of very low birthweight (<1500 g) or born prematurely (<32 weeks) in 16 European centres: a database study

https://doi.org/10.1016/S0140-6736(07)60030-0Get rights and content

Summary

Background

The risk of cerebral palsy, the commonest physical disability of children in western Europe, is higher in infants of very low birthweight (VLBW)—those born weighing less than 1500 g—and those from multiple pregnancies than in infants of normal birthweight. An increasing proportion of infants from both of these groups survive into childhood. This paper describes changes in the frequency and distribution of cerebral palsy by sex and neurological subtype in infants with a birthweight below 1000 g and 1000–1499 g in the period 1980–96.

Methods

A group of 16 European centres, Surveillance of Cerebral Palsy in Europe, agreed a standard definition of cerebral palsy and inclusion and exclusion criteria. Data for children with cerebral palsy born in the years 1980–96 were pooled. The data were analysed to describe the distribution and prevalence of cerebral palsy in VLBW infants. Prevalence trends were expressed as both per 1000 livebirths and per 1000 neonatal survivors.

Findings

There were 1575 VLBW infants born with cerebral palsy; 414 (26%) were of birthweight less than 1000 g and 317 (20%) were from multiple pregnancies. 1426 (94%) had spastic cerebral palsy, which was unilateral (hemiplegic) in 336 (24%). The birth prevalence fell from 60·6 (99%CI 37·8–91·4) per 1000 liveborn VLBW infants in 1980 to 39·5 (28·6–53·0) per 1000 VLBW infants in 1996. This decline was related to a reduction in the frequency of bilateral spastic cerebral palsy among infants of birthweight 1000–1499 g. The frequency of cerebral palsy was higher in male than female babies in the group of birthweight 1000–1499 g (61·0 [53·8–68.·2] vs 49.5 [42·8–56·2] per 1000 livebirths; p=0·0025) but not in the group of birthweight below 1000 g.

Interpretation

These data from a large population base provide evidence that the prevalence of cerebral palsy in children of birthweight less than 1500 g has fallen, which has important implications for parents, health services, and society.

Introduction

Cerebral palsy is the commonest disability of children in western Europe, with a birth prevalence of about two cases per 1000 livebirths. Studies of the patterns of cerebral palsy in relation to birthweight show that infants of very low birthweight (VLBW—ie, less than 1500 g), are between 20 and 80 times more likely to have cerebral palsy than infants of birthweight more than 2500 g.1 Data from Sweden, Australia, and the UK suggest that the prevalence of cerebral palsy among VLBW infants increased during the 1980s,2, 3, 4 and data from the northeast of England5 and the USA,6 seem to show a rise in severity of cerebral palsy in this group of infants. Studies from Denmark,7 Oxford, UK,8 Sweden,9 and Liverpool, UK4 suggest that the prevalence of cerebral palsy in VLBW infants has begun to fall, although studies from other centres in Australia,3, 10 and Atlanta, GA, USA,11 have not shown a fall. Decreased neonatal mortality of VLBW infants is related to improved care of premature infants and has also changed perceptions of viability of these infants. There has also been an increase in multiple births over this period.12 These changes have resulted in a rise in the absolute number of VLBW infants at risk of cerebral palsy.

Previous studies describing the distribution, determinants, and clinical picture of cerebral palsy in VLBW infants included small numbers of infants, which reduced the precision of results and did not allow detailed investigation of the various subtypes of cerebral palsy. Even less information is available about the subset of infants who weighed less than 1000 g at birth (whose survival also improved substantially since the 1980s).13, 14 Thus, little is known about the distribution of cerebral palsy by sex, severity, or neurological subtype in such small infants. Birthweight-specific differences might reflect different origins; very immature infants could be more vulnerable to white-matter damage of different extent and topography than more mature infants and could also be less susceptible to primary cortical damage.15

A collaborative network of cerebral palsy registers and surveys, Surveillance of Cerebral Palsy in Europe (SCPE), was established in 1998. The 16 European centres in this network have developed a standard definition of cerebral palsy (with inclusion and exclusion criteria), and have agreed definitions and descriptions of affected children.1 On the basis of these definitions, the prevalence of cerebral palsy among VLBW infants was calculated as 72·6 per 1000 neonatal survivors (children who survived for longer than 1 month after birth), compared with a prevalence of 1·2 per 1000 among infants of birthweight more than 2500 g.16 The 16 centres provide a large study population, which gives an opportunity to examine the distribution, determinants, and clinical patterns of cerebral palsy among VLBW children. This collaboration showed a non-significant downward trend in the overall prevalence of cerebral palsy at the end of the 1980s,1 and with reports from individual centres suggesting a reduction in prevalence and severity of cerebral palsy among VLBW infants,8, 17 the hypothesis that the birthweight-specific prevalence of cerebral palsy among VLBW infants will have remained stable or fallen further during the 1990s, is reasonable. This paper aims: to describe the epidemiology of cerebral palsy in VLBW infants in detail, looking at those of birthweight less than 1000 g separately from infants of birthweight 1000–1499 g, where possible; to examine changes in the prevalence of cerebral palsy in these two groups over the period 1980–96; and to identify whether the two birthweight groups differ in terms of sex, severity, or neurological subtype.

Section snippets

Methods

The collaboration of centres with data from population-based studies on the prevalence of cerebral palsy in nine European countries has previously been described.1 Case definitions and inclusion and exclusion criteria were agreed in these centres, and data for children with cerebral palsy from 16 European surveys and registers were pooled in a common SCPE dataset. Cerebral palsy was defined as a permanent, but not unchanging, disorder of movement or posture, or both, and of motor function,

Results

16 centres contributed data for children with cerebral palsy to the SCPE database, which covered births in years 1980–96, although not all centres were actively collecting data in all birth years. There were 7884 children with cerebral palsy born between 1980 and 1996 (after exclusion of those with cerebral palsy of post neonatal origin), whose mothers were resident in an area covered by the register at the time of birth or birth registration. Of these children, 2103 (26·6%) were of birthweight

Discussion

Our findings are unlikely to be subject to selection bias associated with hospital-based studies because the data come from population-based centres. This study shows that the survival of infants of birthweight less than 1500 g continues to improve and that this continued improvement is not accompanied by increased morbidity. Although other studies have reported no change in the cerebral palsy rate over time among VLBW survivors to 1 year born between 1975 and 1991,11 the data presented here

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