Do oral contraceptives inhibit Trichomonas vaginalis?

Usage of oral contraceptives was recorded for 114 women with trichomoniasis, 179 women with yeast infection, and 333 women with gonorrhea. Usage by each group was compared with that of 517 women with no genital infection. The proportion of oral contraceptive users was significantly smaller among those with trichomoniasis (P less than 0.002), significantly larger among those with yeast infection (P less than 0.001), but not significantly different among those with gonorrhea. Among 80 women with both trichomoniasis and gonorrhea, a significantly smaller proportion used oral contraceptives as compared with a group of 253 women who had gonorrhea alone (P less than 0.002). The results suggest that oral contraceptives may inhibit trichomoniasis and enhance infection of the vagina by yeasts.