Prevalence of birth defects among low-birth-weight infants. A population study
F. Mili, L. D. Edmonds, M. J. Khoury and A. B. McClearn
Division of Birth Defects and Developmental Disabilities, Centers for Disease Control, Atlanta, GA 30333.
Major birth defects are diagnosed in about 3% to 4% of infants during their
first year of life. Because many infants with birth defects have
intrauterine growth retardation, are born prematurely, or both, the rate of
birth defects undoubtedly varies according to the infant's birth weight.
Nevertheless, the magnitude of such variation has not, to our knowledge,
been adequately studied in well-defined populations. We analyzed data from
the population-based Metropolitan Atlanta (Ga) Congenital Defects Program
for 1978 through 1988. These data included information on 11,398 infants
who were diagnosed with serious birth defects among 317,499 singleton
live-born infants. Although the overall rate of birth defects was 3.6%, we
observed a striking inverse relationship between the birth defects rate and
the infants' birth weights. The birth defect rates were 16.2% for newborns
weighing less than 1500 g at birth, 13.2% for newborns weighing from 1500 g
to 1999 g, 6.2% for newborns weighing from 2000 g to 2499 g, 3.2% for
newborns weighing from 2500 g to 3999 g, and 2.8% for newborns weighing
4000 g or more. Analyses by type of defect indicated that most birth
defects were significantly associated with low birth weight. The higher
risk of birth defects among low-birth-weight infants demonstrates that
birth defects contribute to excess morbidity among low-birth-weight
infants. Because of the overlap between birth defects and low birth weight,
the prevention of low birth weight in the population depends greatly on a
better recognition of the complex etiology of low birth weight and, in
part, on the delineation of risk factors that influence the occurrence of
birth defects.
