Quick Background....My girlfriedn has been taking birth control pills for about a year now....she hasnt missed a pill in a couple of months and started taking her new pack this past sunday. We had unprotected sex on friday night, five days after starting her new pack. I remeber hearing that if taken correctly on the sunday after the period, that the pill becomes effective immediately. I need to know if this is true or not, because i need to know if i should get emergency contraceptive for her. Thanks in advance for you help.

You have written nothing that would indicate a reason for her birth control pills not to work. She hasn't missed any pills and she's been taking them for about a year. Under those circumstances, the pills are going to be about as effective as you can hope. There is no need for emergency contraceptives.

The reason for my concern is that she started her new pack on sunday so she has only been taking the pills for five days. I want to make sure they had enough time to become effective.

IF she's been taking the pills consistently for awhile before she'll be FINE.

That's how you're supposed to take them.

The real risk would lie in if she started her pack late. That's the REAL kicker. Other than that, well, there's that 98% backing her. Depends on if you think 2% is tiny or big enough to drive the starship Enterprise through.

The pills do not become "more" effective over the course of her cycle. They start having their effect immediately. The risk Wrin mentions is a risk that exists at any time during a cycle, and made worse by not taking your pills according to the instructions. There is no more of a reason to avoid sex at the beginning of her cycle than at any other time of her cycle.

The only thing that really comes into play is the consequences if you miss a couple of pills (as in, not just one pill) during whichever week of the pack.

If you miss two pills during the first two weeks it isn't quite as big a deal -- but if you miss two pills during the last week of the pack, stick a fork in ya, you're done -- start a new pack.

As long as she is taking them PRO PER LY she is perfectly okay, like Thisby said.