If you know there is a chance that it can abort babies and still use it or condone the use of it, you are not 100% pro-life. Now, if one changes the definition of when life begins, saying that life begins at some point other than conception or argues that the research involved in determining that hormonal BCs are abortifacient is false, then one could continue to call themself pro-life.
However, believing you are something that you really are not, does not make that something true.
Are you willing to take the risk that the manufacturers’ inserts on these BCs might just be correct? As Ronald Reagan wisely said, “If there’s even a question about when human life begins, isn’t it our duty to err on the side of life?”
Better yet...what would JESUS have you do if there's even a possibility that a life is ended through these methods of birth control?
Proverbs 24:11, 12 "Rescue those being taken off to death, and save those stumbling toward slaughter. If you say, "But we didn't know about this," won't He who weighs hearts consider it? Won't He who protects your life know? Won't He repay a person according to his work?"
Rest assured. God will repay you according to what you knew to be true (or even thought MIGHT be true). Nothing you do is hidden from His sight. Fear God.
Does Life Really Begin at Conception?
Does the Birth Control Pill Cause Abortions?
Ethical Issues Regarding Oral Contraceptives
The Harms of Contraception - From One More Soul