Can a woman pass on syphilis to her newborn without passing it on to her mate?

Not likely: If the baby is delivered vaginally, there is an excellent chance they will acquire the syphilis. There is no reason to think the woman's mate won't also acquire it unless barrier protection (e.g., condom) is used during sexual intercourse. If a woman knows, or suspects, she has syphilis before she gives birth, she needs to talk to her doctor to treat the syphilis before giving birth.

Congenital syphilis: Congenital syphilis is due placental transmition of the the bacterial spirocete pregnant women with secondary syphilis. Theoretically, her mate could avoid catching syphilis because the woman does not have to have open syphilitic chancre sores. Primary or secondary syphilis could be passed on to a child during vaginal delivery due to open sores. Mate could bthen ecome infected if woman untreated.