|Causes and Consequences of Intrauterine Growth Retardation, Proceedings of an IDECG workshop, November 1996, Baton Rouge, USA, Supplement of the European Journal of Clinical Nutrition (International Dietary Energy Consultative Group - IDECG, 1996, 100 pages)|
|Small for gestational age, term babies, in the first six years of life|
Correspondence: Dr SM Grantham McGregor
Centre for International Child Health, Institute of Child Health, 30 Guilford Street, London WC1N 1EH
The cognitive development and behaviour in the
first six years of life of small for gestational age (SGA) babies born at term
are reviewed. Differences in sample selection and confounding factors associated
with socioeconomic background, perinatal complications and biased follow-up make
the interpretation of results and the comparison of studies difficult. Studies
of infants (< 12 months) generally do not show any differences between SGA
babies and controls. One study, carried out in Brazil and including
comprehensive data on socio-economic background, parental literacy and infant
stimulation, showed that low birth weight (LBW) babies were more vulnerable to
effects of the environment than normal birth weight (NBW) babies, thus
illustrating the importance of looking for interactions between covariates,
rather than controlling for them. Deficits begin to appear in the second year of
life, but are mainly found in high-risk subgroups. In all three studies of SGA
children tested at 3 years of age, the SGA children had lower scores than NBW
controls. SGA children tested between 4 and 7 years had generally lower scores
than NBW, but differences were smaller and sometimes did no longer reach
statistically significant levels. Some recommendations are made for future
It is estimated that 16% of births globally are low birth weight (LBW < 2,500 g) and more than 90% of these are in low-income countries. A greater proportion of LBW infants in low-income countries is reported to be small for gestational age than in developed countries (Villar and Belizan, 1982). Although the reported duration of gestational age is often inaccurate (Goldenberg et al, 1989), it is clear that LBW, small for gestational age (SGA) babies are a major problem in low-income countries. The subsequent development of these children is obviously of critical importance both to the future of the children and the individual nations.
There is a burgeoning literature on the development of LBW infants, albeit mainly from developed countries. Aylward et al (1989) conducted a meta-analysis of 80 studies which showed that LBW infants tend to have poorer development than normal birthweight infants (NBW). However they point out many weaknesses with the studies.
There are fewer studies of SGA infants and they have even more problems. IUGR includes infants whose growth is slowed below a certain level for a period of time in utero but reach average birth weights. A few investigators who have studied the children's development have had one ultrasound measure of foetal size (e.g. Nelson et al, 1996). However extremely few have actually assessed growth in utero with repeated ultrasound measurements (e.g. Harvey et al, 1982). At least in developing countries, it is generally not possible to determine whether and when intrauterine growth was retarded; most studies have therefore focussed on babies who are SGA at birth. The WHO recommend using the 10th centile for gestational age as the cut-off to define IUGR (de Onis and Habicht, 1996), however, it is far from clear whether this high cut-off identifies a population at risk of future poor mental development.