This is great. Use the same reasoning to get your wife to buy you a new Corvette C8. Tell her you need it to feel loved and validated, and that it's more valuable than the money. You will be proud of it for years and always show it off. It's not her place to judge you, it made you happy. She needs to spend at least 1 yearly wage on the car or else she doesn't love you.
It is a common understanding throughout the history that women think it is not a fair trade, it is also the case that many men seem to think the women have it harder in the pregnancy period as easy as they may or may not be accused of having it otherwise. Therefore I think you need to add more of an argument for why it should be a fair trade, probably difficult given that when you are taken care of someone (unless in the Pulp Fiction manner) you are doing so because they have it significantly worse than you do.
It's hard to imagine someone saying this if they've ever taken care of a pregnant woman all the way to term. Yes, it's teamwork, but the man gets the better end of the deal and it's not even close.
