Variable   Description  
  bwt       Birth weight in ounces (999 unknown)
  gestation Length of pregnancy in days (999 unknown)
  parity    0= first born, 9=unknown
  age       mother's age in years
  height    mother's height in inches (99 unknown)
  weight    Mother's prepregnancy weight in pounds (999 unknown)
  smoke     Smoking status of mother 
            0=not now, 1=yes now, 9=unknown