Will birth control prevent pregnancy on the first day?

 “i have been off the birth control pill for several months and had unprotected sex today. It really scared me so I started taking the bill again right away. If it is the same day will it prevent pregnancy? Hiw do I know if I should even be concerned about ovulation?”

A: “It takes one week for birth control pills to become active. Anytime you have unprotected sex there is a chance for pregnancy. If you had unprotected sex near the time you were ovulating the risk is greater. Ovulation takes place about 14 days before the start of your period. A sperm cell can live up to 7 days inside your vagina. ALways remember to use protection correctly and everytime you have sex.”