Hereditary illness and kamma
Hereditary illness or not...the offspring you will produce will become old, fall ill and die. The dukkha is inevitable. We may as well say that dukkha is hereditary to all humans so  should we have kids?

If your intention in having a child is good, if the child is born out of love and not lust, if child is born not out of any form of sexual misconduct...then you will be fine...there will be no bad kamma.