Associations of maternal age- and parity-related factors with trends in low-birthweight rates: United States, 1980 through 2000.
OBJECTIVE
We assessed the effects of changes in the maternal age-parity distribution and age-and parity-specific low-birthweight rates on low-birthweight trends in the United States.


METHODS
We used natality file data from 1980 through 2000 to assess very-low-birthweight and low-birthweight rates among singleton live-born infants.


RESULTS
Changes in age-and parity-specific low-birthweight rates were the main contributor to the overall trend in rates. However, changes in the age-parity distribution, primarily delayed childbearing, had a smaller but noticeable impact. The very-low-birthweight rate increased 27% among Black women, and changes in the age-parity distribution were associated with, on average, more than 20% of the increased rate during the 1990s. Among Hispanic and non-Hispanic White women, on average, more than 10% of the rate increase observed during the 1990s was associated with changes in the age-parity distribution.


CONCLUSIONS
Assuming minimal changes in age-specific rates, delayed childbearing may play an increasingly important role in low-birthweight trends in the United States.
Yang
Quanhe
Q
Division of Birth Defects and Developmental Disabilities, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, 1600 Clifton Rd, Mail Stop E-86, Atlanta, GA 30333, USA. qay0@cdc.gov
Greenland
Sander
S
Flanders
W Dana
WD
D000293:Adolescent; D000328:Adult; D044383:Black People; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008423:Maternal Age; D008875:Middle Aged; D010298:Parity; D011159:Population Surveillance; D011247:Pregnancy; D014481:United States / Q000453:epidemiology; D044465:White People; D001741:Black or African American