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Birthweight-Specific Neonatal Mortality Rates -- Kentucky

Studies of birthweight-specific neonatal mortality rates have indicated that rates below 750 per 1,000 live births in the 1,000 g or less birthweight range (1) suggest underreporting of neonatal deaths. In a current study, the degree of underreporting of neonatal deaths and the neonatal birthweight-specific mortality rates for the 1981 Kentucky birth cohort were estimated for low birthweight (LBW) (2,500 g, or less) infants.*

Kentucky recorded 57,294 resident in-state live births in 1981, as determined by a review of the 1981 and 1982 computer birth files. Of these, 4,057 (7.1%) were 2,500 g or less. Among the 4,057 LBW births, 332 neonatal deaths were identified through a computer system for linking infant death and birth files. Subsequently, all LBW birth cohort members not known to have died were grouped by hospital of birth, and a request was mailed to each hospital for classification of births by discharge status (dead, alive to home, or alive to another hospital). Similar requests were sent to hospitals receiving transfers during the neonatal period. Infants classified as discharged dead during the neonatal period and for whom no death certificate could be located were classified as reporting failures.

Fifteen unreported neonatal deaths were identified by 11 different hospitals, one of which had three unreported deaths (Table 2). No significant trend in underreporting by birthweight was found. An additional 18 neonatal deaths could not be classified by birthweight because of lack of information. Reported by CW Spurlock, Div of Epidemiology, MW Hinds, MD, State Epidemiologist, Kentucky Dept of Health Svcs; GH Bergeisen, Indian Health Svc, Bemidji, Minnesota; Program Evaluation Br, Pregnancy Epidemiology Br, Div of Reproductive Health, Center for Health Promotion and Education, CDC.

Editorial Note

Editorial Note: The birthweight-specific mortality rates observed in Kentucky are roughly comparable to rates reported during similar periods in other southern states that link birth and infant death certificates (2-4).

These findings indicate that current neonatal mortality rates below 750 per 1,000 live births in the 1,000 g or less weight range do not necessarily indicate underreporting and may reflect continuing advances in perinatal care for very small infants.


  1. McCarthy BJ, Terry J, Rochat RW, Quave S, Tyler CW Jr. The underregistration of neonatal deaths: Georgia 1974-1977. Am J Public Health 1980;70:977-82.

  2. Goldenberg RL, Humphrey JL, Hale CB, Boyd BW, Wayne JB. Neonatal deaths in Alabama, 1970-1980: an analysis of birth weight- and race-specific neonatal mortality rates. Am J Obstet Gynecol 1983;145:545-52.

  3. Georgia Council on Maternal and Infant Health, Office of Health Planning and Statistics. The perinatal data book, trends and measures, 1972-1981. Atlanta, Georgia: Department of Human Resources, 1983.

  4. Buescher PA. The impact of low birth weight on North Carolina neonatal mortality. State Center for Health Statistics (special series no. 30). Raleigh: North Carolina Department of Human Resources, 1983. *In 1979, the National Center for Health Statistics recommended that the definition of low birthweight be changed from 2,500 g or less to less than 2,500 g to comply with the International Classification of Diseases, 9th Revision. National vital statistics are reported using the less than 2,500 g definition; however, the 2,500 g or less definition has been recently used by the Institute of Medicine for comparison with previous years.

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