I think ideally, people should be aware of where their significant other stands on the subject of abortion and having children. Nobody is "trapped" in childlessness but plenty of people betray their spouses because they decide reproducing is more important to them than the one they entered a marriage into under the guise of "love".
I think that if a woman can't trust her spouse to tell him she's pregnant/wants to abort then there's something deeper wrong with the relationship than someone just changing their mind.
Nobody can tell the future and a lot of people enter a marriage under the assumption that there will be children...which is a mistake in itself even if BOTH parties want offspring. Most people don't even know they're infertile until they start trying to get pregnant.
Either they change their mind and start giving the other party ultimatums: "Agree to get pregnant/get me pregnant or this can't work!"
Or one of them finds out he/she is sterile and the other dumps them (I REALLY hate people that pull this crap) for another stud or broodmare.
It's equally repulsive when one spouse tries to get pregnant or impregnate the other on the sly without their consent. I consider that to be just a step below rape and in the case of the woman, the man is actually risking her health by trying to put her in a condition that puts a strain on her body.
People should always find out where their partners stand on the issue but there are cases where people change their mind one way or the other later on down the line. I would hope that when they claimed to love their spouse in their marriage vows, they meant it enough to stick it through and find a workable solution for everyone.
I think some people take the term wed"lock" a bit too literally, though. It's like the old joke about the "ball and chain".