 [ Symptoms ] what if you have unprotected vaginal intercourse within 24 hours of starting birth control  i took my first pill within 24 hours of having intercourse with my boyfriend i am continuing to take the pills on my set schedule what maybe the percentage that i end up pregnant [ Disease ] you might as not even be on the pill if you have unprotected sex with in 24 hours like most pills it takes a while to take effect in your system good rule of thumb is allow a month from time started for it to enter and take effect in your system until then us a condom