Haematology Lesson Poem by Herbert Nehrlich

The question was what is Rh,
it is a bloody factor
that can destroy an unborn life
in a most painful way.
If father has the factor,
and mother is a minus
the baby may inherit
the father's blood, a plus.
The mother then detects
this foreign factor quickly
and gets her panzers ready
that's how it works my friend.
There is no other option
so learn this simple fact
the mother must be minus
the father needs a plus.