Congenital malformations - Edocr

4 PART I GENERAL CONSIDERATIONS
TABLE 1-1 Incidence of Major Malformations
in Human Organs at Birth
Organ
Incidence of Malformation
Brain 10:1000
Heart 8:1000
Kidneys 4:1000
Limbs 2:1000
All other 6:1000
Total 30:1000
two decades but the overall total prevalence of
major malformations has been unchanged. 8–10
Other studies have reported a gradual decline
in the total prevalence of nonchromosomal and
an increase in chromosomal anomalies. 11,12 No
consistent evidence of seasonality has been reported
for common birth defect groups. 13
A higher overall rate of birth defects is reported
in males and black infants. 14,15 Another study
from the UK reported a higher risk of congenital
anomalies of nonchromosomal origin with increasing
socioeconomic deprivation and speculated
that this increase in risk was probably related
to differences in nutritional factors, lifestyle,
environment and occupational exposures, access
to healthcare, maternal age, and ethnicity. 16
However, more research is necessary to confirm
these findings and to better understand the
reasons for the increased risk of congenital
malformations with increasing socioeconomic
deprivation, if any.
Detailed information from population-based
studies on the incidence and prevalence of minor
malformations is limited, less reliable, and
less accurate because of difficulties and inconsistencies
in definitions, identification, documentation,
and reporting of these non–lifethreatening
birth defects. The incidence of
minor malformations has been reported to vary
from about 7% to as much as 41% among newborn
infants. In addition, the majority of birth
defect registries collect data only on congenital
anomalies diagnosed before, at, or soon after
birth; few collect data on cases diagnosed from
birth to the age of 1 year. However, many minor
malformations of internal organs are diagnosed
later in life, if at all.
Contribution of Birth Defects to
Infant Mortality
Congenital malformations are an important cause
of infant death, both in absolute terms and as a
proportion of all infant deaths, in both the developed
and developing world. Although only
a small percentage of all newborns, 2–3%, are
born with a major congenital malformation, congenital
malformations account for nearly 20% of
all infant deaths in developed countries. Based
on WHO data from 36 countries from different
continents, overall infant mortality decreased
on average 68.8% from 1950 to 1994 but infant
mortality attributable to congenital anomalies
decreased only 33.4%. Infant mortality attributable
to congenital anomalies was higher in developing
countries than in developed countries
but as a proportion of all deaths, infant mortality
attributable to congenital anomalies was
higher in developed countries. 1 The data from
the United States and Canada show that infant
deaths caused by major congenital malformations
have decreased significantly over the last
several decades but birth defects remain the
leading cause of infant death and account for
nearly 20% of all infant deaths in these countries.
15,17 Birth defects are the leading cause of
death among whites, Native Americans, and
Asian Americans in the United States but the infant
mortality rate related to birth defects for
black infants is higher than the corresponding
rates for infants of other races. 15
Very few studies have addressed the survival
data beyond infancy for children born with congenital
anomalies. A recent report concluded
that the overall relative risk of mortality was
higher in children with congenital malformations
compared to children without congenital
malformations, and this risk of mortality was
highest during the second year of life and remained
high through the end of the sixth year. 18