First of all, pray and ask God for direction and wisdom and for your pastor to be receptive to the information.
Present it in a way that is not offensive or accusatory. Know that a pastor’s life is very busy and he deals with many different issues. He most likely hasn't had the time to do research on this issue himself.
Encourage him to at least make the information available to his people and let them decide. We’ve heard from many who have been very distraught after finding out about the potential abortifacient nature of the pill who had been previously told by their pastor or youth leader that the pill was completely fine to use.
You are helping him by providing him with some important information to consider before the Lord. It’s up to the Lord to direct him as to what to do with it.
For more information on this subject, see Randy Alcorn's books Why ProLife?, ProLife Answers to ProChoice Arguments, and Does the Birth Control Pill Cause Abortions?
Randy Alcorn (@randyalcorn) is the author of over sixty books and the founder and director of Eternal Perspective Ministries.