Immune cells will be studied from the reproductive tract of women who want to start using one of the following contraceptives: an oral contraceptive pill (COC), Depo-Provera (DMPA), the levonorgestrel IUD (Mirena®), the copper IUD (ParaGard®), or the etonogestrel subdermal implant (Nexplanon®).Immune cells will also be studied from the reproductive tract of women who are not using birth control and who are not at risk of pregnancy for comparison.