Approximately 3%-4% of newborn infants have a major birth
defect
diagnosed during their first year of life (1). Because many infants
with birth defects are born prematurely and/or have intrauterine
growth
retardation (2-5), the rate of birth defects is expected to vary by
birth weight. This report summarizes a population-based study of
the
relation between birth defect rates and the birth weight of infants
born in metropolitan Atlanta from 1978 through 1988.
Data from the population-based Metropolitan Atlanta Congenital
Defects Program (MACDP) for 1978-1988 were used to study the rate
of
birth defects in infants in five birth-weight categories (less than
or
equal to 1499 g (less than or equal to 3 lbs 4 oz), 1500-1999 g (3
lbs
5 oz-4 lbs 7 oz), 2000-2499 g (4 lbs 8 oz-5 lbs 7 oz), 2500-3999 g
(5
lbs 8 oz-8 lbs 13 oz), and greater than or equal to 4000 g (greater
than or equal to 8 lbs 14 oz)). The MACDP ascertains birth defects
among all infants whose mothers reside in one of five counties of
the
metropolitan Atlanta area. Cases include live-born and stillborn
infants (greater than or equal to 20 weeks gestation or weighing
greater than or equal to 500 g (1 lb)) with major or serious
structural
defects diagnosed in the first year of life (6). However, this
analysis
was restricted to live-born singleton infants. Birth defect rates
were
determined by dividing the number of singleton live-born infants
with
birth defects registered in the MACDP during 1978-1988 by the total
number of singleton live births in the five-county metropolitan
Atlanta
area during the same period. Rate ratios (RRs) were calculated by
dividing the rate of birth defects for infants in each birth-weight
category by that of infants weighing 2500-3999 g.
Overall, 3.6% of singleton infants born in metropolitan Atlanta
during 1978-1988 had major birth defects. Infants in
low-birth-weight
(LBW) classes (less than or equal to 2499 g) were at 1.8 times
higher
risk of having birth defects than were those weighing 2500-3999 g
(95%
confidence interval (CI)=1.7-1.8). Specifically, 17% of white
infants
(RR=5.8) and 16% of infants of other races (RR=4.4) weighing less
than
or equal to 1499 g had birth defects; 16% of white infants (RR=5.3)
and
12% of infants of other races (RR=3.3) weighing 1500-1999 g had
birth
defects; and 7% of white infants (RR=2.4) and 6% of infants of
other races (RR=1.6) weighing 2000-2499 g had birth defects (Table
1).
Infants weighing greater than or equal to 4000 g were at a slightly
lower risk of having birth defects than were those weighing
2500-3999 g
(RR=0.9; 95% CI=0.8-0.9). Measures of the association between birth
weight and birth defects did not vary when stratified by maternal
age,
birth period, and infants' sex. In addition, analyses by type of
defect
indicated that 26 of the 37 specific defects examined were
associated
with LBW (p less than 0.05).
Reported by: Birth Defects and Genetic Disease Br, Div of Birth
Defects
and Developmental Disabilities, Center for Environmental Health and
Injury Control, CDC.
Editorial Note
Editorial Note: The findings in this report indicate that, although
the
overall rate of serious birth defects in singleton live-born
infants
born in metropolitan Atlanta was 3%-4%, the rate varied greatly by
birth-weight category. These findings have implications for
clinical
care, surveillance, and prevention. First, birth defects contribute
to
increased morbidity and mortality among LBW infants and are often
associated with costly medical and surgical care that compounds
medical
problems related to LBW. Second, an increasing number of statewide
programs are conducting or planning birth defect surveillance
activities. Because LBW infants are at high risk for birth defects,
targeting medical records of LBW infants should improve the overall
ascertainment of birth defects in the population. Finally, because
a
substantial proportion of LBW infants have associated birth
defects,
public health prevention strategies targeted at LBW should consider
the
complex etiology and pathogenesis of LBW and attempt to better
delineate and prevent risk factors that influence the occurrence of
birth defects.
References
CDC. Congenital malformations surveillance report: January
1982-December 1985. Atlanta: US Department of Health and Human
Services, Public Health Service, 1988.
Kliegman RM, Behrman RE. The high risk infant. In: Behrman RE,
Vaughn VC III. Nelson textbook of pediatrics. 13th ed.
Philadelphia: WB
Saunders, 1987:373-85.
Edmonds LD, Layde PM, James LM, et al. Congenital malformations
surveillance: two American systems. Int J Epidemiol 1981;10:247-52.
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