age1,age2,age3
:Orthogonal polynomials of
first, second, and third degree representing mother's age in
years
lwt1,lwt2,lwt3
:Orthogonal polynomials of
first, second, and third degree representing mother's weight in
pounds at last menstrual period
white,black
:Indicator functions for mother's race;
"other" is reference group
smoke
:Smoking status during pregnancy
ptl1,ptl2m
:Indicator functions for one or for two or
more previous premature labors, respectively. No previous
premature labors is the reference category.
ht
:History of hypertension
ui
:Presence of uterine irritability
ftv1,ftv2,ftv3m
:Indicator functions for
one, for two, or for three or more physician visits during the
first trimester, respectively. No visits is the reference
category.