I think it depends who decided you should be a SAHM, what the other options are, and how you and your DH both feel about them.
If you both think it is best that you be a SAHM, then I don't think it is unreasonable that your financial future is as secure as his is. That is both of your responsibility.
If being a SAHM is your decision and he would prefer you to keep working or to do shared care, then it is a bit more difficult to make that argument, I think.