The less govt interfering with peoples lives , the better it is.
Govt cannot decide who can or cannot procreate, force someone to have a medical procedure, or who can and cannot abort a pregnancy. Unfortunately the (unborn)child in cases of abortion or hiv parents has no rights until after it is born alive.
The govt cannot gaurantee anything anytime, what if the couple become HIV carriers after the wedding? It will be upto the people concerned to make moral or ethical judgements about themelves and what kind of future their children will face consequently as a result of their actions.