TABLE 1.

Characteristics of the Study Population (n = 20 366 Mother-Infant Pairs)

VariablePercentage
Maternal age (y; n = 20 357)
 <224.5
 22–2931.2
 30–3439.2
 35+25.1
Primiparous mother (n = 15 888)44.6
Enrolled in Medicaid (n = 20 355)6.7
Census-based SES indicators (n = 20 087)
 Living in low-income tract*6.7
 Living in low-education tract19.9
Race/ethnicity (n = 19 993)
 White69.2
 Black17.0
 Asian6.6
 Hispanic, non-black4.9
 Other2.2
Birth weight (g; n = 20 207)
 <25002.7
 2500–299912.9
 3000+84.4
Gestational age (wk; n = 17 245)
 <386.6
 38–3927.1
 40+66.3
5-min Apgar score (n = 19 083)
 <81.7
 86.7
 9–1091.6
  • * Median 1990 household income in census tract <$25 000.

  • Twenty five percentage or more of people aged 25+ years in census tract have no high school diploma or equivalency.