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.
Today's enlisted people know in advance what will be required, including vaccinations. If birth control is mandatory, a female enlistee would give informed consent to medication at enlistment. Disobedience at a later date is a different matter.
BTW, why the assumption that enlisted people, male or female, lack sexual self control? Many people are perfectly able to control themselves, particularly if they are married. Why force those individuals to take drugs they do not need?