When diagnosed and treated early on, syphilis typically does not pose a huge risk to reproductive or overall health. Unfortunately, if left untreated a variety of health complications can develop especially in the later stages of infection as listed on the Mayo Clinic site.
Bumps or tumors on internal organs and bones
These bumps, called gummas, can appear on any internal organs, skin and bones. Typically with treatment these will go away.
Increased risk of HIV infection
Since most commonly syphilis causes open sores that may bleed easily, the likelihood of becoming infected with the HIV virus increases (nearly 2 to 5) since the pathway for blood (and other bodily fluids from an HIV positive person) to travel becomes a direct one.
Late stage syphilis can result in stroke, dementia, mood and personality changes, deafness, visual problems, meningitis and paralysis.
As a result of the infection, aneurysm and inflammation of the aorta and other blood vessels can occur.
Pregnancy and childbirth problems
Nearly 40% of babies born with syphilis (contracted from their mother) die as a result of miscarriage, stillbirth or infection in the first few days after birth. Many will be born prematurely.