Sure it's deceitful, when women and when men *trick* their partner. But I bet it happens a lot and is called an *accident*.
Bring in the male contraceptive pill!
Assuming a couple decides the number of children they want up front, then it would seem the most practical thing to do once the quota has been reached is for the guy to go get the snip. No more contraceptive hassle! If they don't, then there's always going to be the chance of pregnancy again because we all know contraception can fail (or we can slip up with it!).
On the other hand, if they only make the decision to have 2 children, after the fact, then that's more of an a grey area as who's to say who's decision is more valid? Especially if they discussed having *lots* of kids beforehand then one changed their mind after 2 kids. People do need to take more responsibility for their own contraception though - if they feel that strongly about it.