Why can’t some women coming off the pill get pregnant?

1/10 women have or will develop PCOS, when they come OFF the pill, they will have difficulty getting pregnant (though ironically the first month off the pill is the most fertile for them) but it will NOT be due to the pill but their underlying PCOS.

Also, the pill, patch, vag ring, etc do NOT protect against STDs (sexually transmitted diseases) so if you get Chlamydia and don’t know it, then that would affect your future fertility and again it wouldn’t be the pill causing the issue. So always use a condom.