Both realistic ideas.
OR there needs to be some other solution in order to prevent the pregnancy.
If so it should be voluntary. Forced drugging is totalitarian. If military service is voluntary and the rules are known at enlistment that's one thing. Even so, I believe soldiers who refuse vaccines are either placed elsewhere or discharged. I don't know of any who are held down and injected against their wills. This is especially important if a draft becomes involuntary. You cannot forcibly drug another human being except in extremely limited circumstances.
Last I checked you got an Article 15 if you refused a vaccine. And there were threats of fines, demotions, etc, etc
It is possible, (but it will never happen in this PC military) that IF crew were made to sign a statement swearing that THEY WILL NOT get pregnant, and if they do, both they AND the father will be subject to fines, busts in rank and that the military WILL NOT pay for their pre-natal care, THAT might have an effect.
Like the poster at the top of the thread said, too many people are using the pregnancy as a way to get a cushy slot and out of an unpleasant situation.