mother's age, years
mother's educ, years
month prenatal care began
total number of prenatal visits
father's age, years
father's educ, years
birth weight, grams
one minute apgar score
five minute apgar score
avg cigarettes per day
avg drinks per week
=1 if bwght <= 2000
=1 if bwght <= 1500
=1 if baby male
=1 if mother white
=1 if mother black
=1 if mother is other
=1 if father white
=1 if father black
=1 if father is other
log(bwght)
mage^2
npvis^2