Frequencies for first 10,000 rows of pregnant variable in nhamcsed1999 dataset :

 if female, |
 is patient |
  pregnant? |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        278        2.78        2.78
          2 |      3,218       32.18       34.96
          3 |      1,665       16.65       51.61
          4 |      4,839       48.39      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016