YES!!! Both of my children were conceived while I was on the pill. But let me first say, I was not on a *normal* pill. All birth control pills make me extremely nauseous. At the time, the only one that didn't bother me was Micronor, which is a progesterone only pill. I knew that its efficacy rate was 96% versus 99.9% like regular pills. I thought "heck, 96% is pretty good." What they neglected to tell me was that when taking Micronor, you have a VERY NARROW pill-taking window. Meaning, you pretty much have to take the pill at the exact same time every day. If you are as much as 1-2 hours off of your schedule, this can cause you to conceive. Other pills are not that restrictive. Anway, I did not know this. I will say, I took those pills faithfully every day. But, I'm sure on the weekend I took it a bit later in the morning. After being on this pill for 3 years, I conceived my DD. I thought it was an odd fluke and would never happen again. So, after she was born I took it again. Three years later, DS was conceived. At this point, I moved and changed OB/GYNs and told him my saga. He said he would NEVER put a patient on Micronor as a *serious* birth control. He only gave it to breastfeeding women who needed some extra protection. Great! Well, to answer you question, both times I was pregnant I still missed my period even while on the pill.