C31G is an effective spermicide with in vitro activity equal to that of N-9 . C31G has been found to be a broad-spectrum antibacterial agent in vitro or in animals, active against both gram-positive and gram-negative organisms, including chlamydia, and a range of antibiotic resistant strains. It is also active against enveloped viruses including HIV and HSV. Thus, the primary objective of the study is to determine the contraceptive efficacy of C31G vaginal gel compared to Conceptrol® Vaginal Gel. The secondary objectives are to determine the safety and acceptability of the compounds with use over a period of six months or twelve months. Additional evaluations include the incidence of urinary tract infections (UTI), bacterial vaginosis (BV) and yeast vaginitis following the use of C31G vaginal gel compared to Conceptrol® Vaginal Gel.