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Birth Defects among Low Birth Weight Infants -- Metropolitan Atlanta, 1978-1988

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.


  1. CDC. Congenital malformations surveillance report: January 1982-December 1985. Atlanta: US Department of Health and Human Services, Public Health Service, 1988.

  2. 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.

  3. Creasy RK, Resnik R. Intrauterine growth retardation. In: Creasy RK, Resnik R, eds. Maternal fetal medicine: principles and practice. Philadelphia: WB Saunders, 1984:491-510.

  4. Khoury MJ, Erickson JD, Cordero JF, et al. Congenital malformations and intrauterine growth retardation: a population study. Pediatrics 1988;82:83-90.

  5. Creasy RK. Preterm labor and delivery. In: Creasy RK, Resnick R, eds. Maternal fetal medicine: principles and practice. Philadelphia: WB Saunders, 1984:415-43.

  6. 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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