The Collaborative International Dictionary of English v.0.48:

birth control \birth control\ n.
   the act or process of deliberately limiting the number of
   one's children born, especially by preventing conception.

   Note: Conception may be prevented by ingesting medicines,
         using barriers such as condoms or spermicides during
         copulation, or by ligating or removing the reproductive
         organs.

   Syn: birth prevention, family planning.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

birth control
    n 1: limiting the number of children born [syn: birth control,
         birth prevention, family planning]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "birth control":
   aridity, barrenness, contraception, dearth, dry womb, dryness,
   family planning, famine, impotence, ineffectualness, infecundity,
   infertility, planned parenthood, rhythm method, sterileness,
   sterility, the pill, unfertileness, unfruitfulness,
   unproductiveness, vasectomy, withered loins