INVESTIGADORES
BELIZAN Jose
artículos
Título:
Risks for low intellectual performance related to being born small for gestational age are modified by gestational age.
Autor/es:
BELIZÁN JM
Revista:
PEDIATRICS
Referencias:
Año: 2006 vol. 118 p. 433 - 434
ISSN:
0031-4005
Resumen:
Risks for Low Intellectual
Performance Related to Being Born
Small for Gestational Age Are
Modified by Gestational Age
To the Editor.
In an article published in the March 2006 issue of Pediatrics,
Bergvall et al1 show information to conclude that
during early stages of gestation, growth in length and
head circumference may be more important for intellectual
development than weight increase. They arrive at
this conclusion from a population-based cohort study
conducted in 352 125 boys in Sweden that showed that
men who were born preterm with a very low birth
weight for gestational age were not at increased risk for
low intellectual performance, but those with a very short
birth length or a very small head circumference for
gestational age faced a nearly doubled risk for low intellectual
performance compared with their appropriate
peers.
We would like to add to this discussion the results of
epidemiologic studies performed by our group, which
show information about postnatal behavior linked to the
period during pregnancy in which the deterioration in
growth took place and also related to the etiologic factors
implied in this growth retardation.
In an article published in 1982, intrauterine length
and weight growth were shown to have different periods
of major growth during pregnancy.2 The peak in the
velocity of length growth is at 16 weeks of pregnancy,
whereas weight increase shows its maximum value atPediatrics,
Bergvall et al1 show information to conclude that
during early stages of gestation, growth in length and
head circumference may be more important for intellectual
development than weight increase. They arrive at
this conclusion from a population-based cohort study
conducted in 352 125 boys in Sweden that showed that
men who were born preterm with a very low birth
weight for gestational age were not at increased risk for
low intellectual performance, but those with a very short
birth length or a very small head circumference for
gestational age faced a nearly doubled risk for low intellectual
performance compared with their appropriate
peers.
We would like to add to this discussion the results of
epidemiologic studies performed by our group, which
show information about postnatal behavior linked to the
period during pregnancy in which the deterioration in
growth took place and also related to the etiologic factors
implied in this growth retardation.
In an article published in 1982, intrauterine length
and weight growth were shown to have different periods
of major growth during pregnancy.2 The peak in the
velocity of length growth is at 16 weeks of pregnancy,
whereas weight increase shows its maximum value at1 show information to conclude that
during early stages of gestation, growth in length and
head circumference may be more important for intellectual
development than weight increase. They arrive at
this conclusion from a population-based cohort study
conducted in 352 125 boys in Sweden that showed that
men who were born preterm with a very low birth
weight for gestational age were not at increased risk for
low intellectual performance, but those with a very short
birth length or a very small head circumference for
gestational age faced a nearly doubled risk for low intellectual
performance compared with their appropriate
peers.
We would like to add to this discussion the results of
epidemiologic studies performed by our group, which
show information about postnatal behavior linked to the
period during pregnancy in which the deterioration in
growth took place and also related to the etiologic factors
implied in this growth retardation.
In an article published in 1982, intrauterine length
and weight growth were shown to have different periods
of major growth during pregnancy.2 The peak in the
velocity of length growth is at 16 weeks of pregnancy,
whereas weight increase shows its maximum value at2 The peak in the
velocity of length growth is at 16 weeks of pregnancy,
whereas weight increase shows its maximum value at
33 weeks of pregnancy. As a consequence, at the end
of the second trimester of pregnancy, length has reached
71% of the mean length at term, whereas weight is only
32% of the term infant weight. Consequently, 2 different
patterns of intrauterine growth-restricted (IUGR)
newborns can be distinguished: those with low height
and weight and those with almost normal length and
low weight, proportionate and disproportionate growth
restriction, respectively. This pattern is related to the
period of the growth restriction, and consequently, proportionate
ones suffered a restriction all over pregnancy
(chronic), whereas the disproportionate suffered growth
restriction mainly in the third trimester of pregnancy
(subacute).
The etiology of these 2 different types of growth restriction
is different. The chronic types are related to
maternal chronic malnutrition, smoking from early
pregnancy, genetic factors, and maternal vascular diseases.
Main causes associated with fetal growth restriction
during the third trimester of pregnancy are pregnancy-
induced hypertension, preeclampsia-eclampsia,
and relatively well-nourished women with low weight
gain during pregnancy.233 weeks of pregnancy. As a consequence, at the end
of the second trimester of pregnancy, length has reached
71% of the mean length at term, whereas weight is only
32% of the term infant weight. Consequently, 2 different
patterns of intrauterine growth-restricted (IUGR)
newborns can be distinguished: those with low height
and weight and those with almost normal length and
low weight, proportionate and disproportionate growth
restriction, respectively. This pattern is related to the
period of the growth restriction, and consequently, proportionate
ones suffered a restriction all over pregnancy
(chronic), whereas the disproportionate suffered growth
restriction mainly in the third trimester of pregnancy
(subacute).
The etiology of these 2 different types of growth restriction
is different. The chronic types are related to
maternal chronic malnutrition, smoking from early
pregnancy, genetic factors, and maternal vascular diseases.
Main causes associated with fetal growth restriction
during the third trimester of pregnancy are pregnancy-
induced hypertension, preeclampsia-eclampsia,
and relatively well-nourished women with low weight
gain during pregnancy.22
Follow-up studies evaluating intellectual perfor-
mance of these different groups of newborns showed
that those with chronic intrauterine growth restriction
showed significantly poor performance.3535
In conclusion, we wish to add to the contribution of
this article that the association found with intellectual
performance and fetal length restriction could be linked
to the period during pregnancy in which such growth
was restricted and to the etiology associated with such
restriction.
Finally, we would like to mention that these findings
are of great concern for developing countries. These
countries have a great proportion of children born with
growth restriction. In addition, we have shown that
populations in developing countries have a higher incidence
of chronically malnourished neonates (proportionate
growth restriction) within their IUGR population
(67%79% of the IUGR population), whereas populations
in developed countries have a predominance of
subacute fetal malnutrition, with the proportion of
chronically malnourished newborns being only 20% to
40% of the total IUGR population.66
Jose´ M. Beliza´ n, MD, PhD
Department of Mother and Child Health Research
Institute for Clinical Effectiveness and Health Policy
Viamonte 2146 (3er Piso)
C1056ABH Buenos Aires, Argentina
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Risks for low intellectual performance related to being born
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doi:10.1542/peds.2006-0697