It takes both a man and woman for a baby to be created. It is both of their right/responsibility to do what it takes either for the baby to be made or prevented.
Having an abortion is a surgery that is completed. Voluntarily. Since the woman bares the responbility of carrying the baby, it is utlimately HER health which is impacted. The woman has a choice about what happens to her body.
Note that the above statements are TWO distinct things which happen at different times. They are not mutually exclusive therefore the man really has only ONE opportunity to decide he does not want a baby. That lies at the time of the act, not at the time of potential for abortion.