A friend asked me concerning Karma:

"You are telling me that all the babies who are born mentally retarded or missing limbs 'deserve' this, and that it is not, for instance, chance, or a result of unhealthy maternity?"
The Buddha stated three things which are misunderstandings about karma ---that everything:
1) Is here due to no reason
2) Is the creation of a god
3) Is completely controlled by karma (so it becomes like a fate).
We can go on and on about how people suffer, whether someone is born without an arm or whether one is persecuted during a war or holocaust. I think the misunderstanding is the person who asked you the question is assuming that karma is a fate system. Karma is not a fate system.
Karma plants a seed, and when certain conditions are around, that karmic seed ripens. Your life is not predetermined.
If one assumes any of those "three misunderstandings" the question seems right. If everything is here due to no reason, it would be a very sad that someone is born in a very bad condition. If everything is due to a God's creation, it is horrible that God allowed this to take place and allowed such bad conditions to take place. If everything is a fate system, then we are merely robots who have not much control over the outcome of anything.
But Buddha taught none of these, and karma does not fall into these misunderstandings. The seed for the particular karma was present and was able to ripen under the conditions (such as an unhealthy maternity)... not because it was predetermined!