Impact of Delayed Pill Intake on Birth Control Effectiveness

Question
Hello,

I have been taking a combo pill called kelnor (generic for ortho tri-cyclen) for about 6 months now. I have taken it every day and never missed, but on 3 separate and far between occasions I took it at slightly differing times. My set time to take the pill is 9 PM every night (literally within in the minute on my clock). Two nights (not in a row) I took it later at about 9:30 PM, and on one occasion I took it at 11:30 PM. This is all within this six month time frame.

I am 20 years old, never pregnant, and haven't had sexual intercourse in over 4 years. However, my boyfriend and I have our first year anniversary coming up in about 2 weeks and it is very possible that we will have sex. He is a virgin but I am not. I have seen varying figures on the efficiency of the pill as a stand alone method (99.9% effective with 'perfect' usage, around 97% with 'normal' usage, but some figures even as low as 87% if you miss and such) so I am unsure what information to trust.

My question is, will we be okay using the pill as a stand alone method, or should we invest in a back up form of birth control as well for our anniversary weekend together? He lives far away from me, we don't see each other as often as we'd like but I am very faithful about taking my pill. My biggest concern is preventing pregnancy. Any help would be greatly appreciated.

Thanks,
Crystal

Answer
Hi Crystal,

Those 3 nights that you took the pill a little later would not have reduced the pill's effectiveness. For combo pills (estrogen and progestin) you have a 4 hour window to take the pill. Even if you take it beyond that window, if it is just once and not several days in a row you are fine. As you have found out, when used alone, the pill has an effectiveness of over 99% with "perfect" use. For "typical" usages I usually see rates of 92%-97%. I have not seen anything as low as 87%. Remember, those falling in the "typical" usage are women who miss pills, take it while on antibiotics, etc. There is a range of experiences in that group. Someone on your schedule does not need a back-up method. However, if this is your first time with your boyfriend and you are nervous and worried about pregnancy, using a condom may help ease that concern.

I hope this helps. If you have further questions let me know.

-Mia