Is it considered a sin or forbidden to suffice with two daughters and not have more children, given a health excuse that prevents one from properly caring for the children and the husband?

Procreation is one of the greatest purposes of marriage and a shared right between spouses. There is no harm in agreeing to delay or regulate it for a [valid] reason. If procreation causes harm to the woman or excessive hardship, then there is no sin in refraining from it.