If salmonella gets in the vagina or in the cervix when pregnant or just before becoming pregnant, as in during luteal phase, could it harm the fetus?

Vaginal salmonella?: The only way salmonella can reside in the vagina, is if it was extruded rectally and found its' way into vagina. Small amounts of several Gram negative bacteria that are normally disease producing(pathogenic) in other body locations are often found in the vagina. The cervix and later a pregnant mucous plug keeps those organisms away from the developing fetus unless there are overwhelming amounts.

Potentially: This would be very unusual but potentially any infection in the cervix might hurt the fetus. Note that there is a cervical plug that acts as a barrier to infection that does help. I am not sure how this would be introduced but if this is a major concern then ask your ob doctor. Best wishes