When my wife was about 3 months pregnant I (straight man) with no STDs had intimate contact with a woman (colleague) other than my wife.  She gave me a blow job. We kissed, I gave her oral sex on her vagina.  I fingered her as well.  Since then I have only kissed my wife and we never had any intimacy other than kissing.  I read that you can spread syphilis or other STDs through kissing.  Do I need to get tested.  We were both tested for STDs while she was trying to get pregnant as we were doing IVF.  What are the chances of me getting syphilis from this girl I fooled around with one time and then passing it on to my wife by kissing? My wife is 7.5 months pregnant I want to make sure she and baby are okay.  I would never do this again. 

In a way, you are right to be concerned about syphilis on account of your wife's pregnancy. Syphilis rates have been rising dramatically, and there has been a serious increase in the frequency of congenital (i.e. newborn) syphilis in the US. https://www.washingtonpost.com/health/2022/05/01/syphilis-babies/

However, it remains a rare problem; 2,300 cases annually in the US is a teeny percentage of roughly 4 million births per year. And congenital syphilis is largely restricted to populations at particular risk, e.g. undocumented immigrants who delay care for fear of drawing attention to their status; injection drug users; and so on. And the large majority of syphilis in the US still occurs in men who have sex with men.

The chance a partner like you describe has syphilis is zero for all practical purposes, and fingering, kissing, and oral sex carried little risk even if she was infected. And if I understand the timing -- around 4 months since your extramarital sexual event -- if you had acquired syphilis, you would have noticed a primary lesion (called a chancre) at an exposed site, like your penis or mouth. So you can be very sure you don't have it and can safely continue to be intimate with your wife, including unprotected intercourse. Also, your wife probably has been tested for syphilis, which is automatic for almost all obstetricians in caring for their pregnant patients. (If you would like an extra measure of safety, you could have a syphilis blood test. But your risk is so low that I consider this optional, not required. It's up to you.)

So all is well. Best wishes to you and your wife for successful conclusion of her pregnancy and a healthy baby. I hope this information is helpful. Let me know if anything isn't clear.

HHH, MD

At the very slightest chance if I was exposed and infected 

Would I have to show symptoms to be contagious? 

Maybe in the first stage there was a small chancre I may have missed on my tongue. Would there always  be a  secondary symptoms like a rash? 

I didn't have that, so does that certainly Confirm I didnt have it?

I am getting tested just to be sure? 

In the rarest chance I had it, could I still spread to my wife through kissing? 

Also if she did have it, what would she have to do being 7.5 months pregnant. 

I'm almost sure I don't have it but I want to know what I must do if I or she (wife) has it? 

And would have definately noticed it on my penis? 

It's unlikely you would have missed a chancre on either your tongue or penis. Chancres typically grow to a cm or more in diameter, with swelling around it, and last 2-4 weeks. (You can google "chancre images" or similar wording to see lots of photos of typical lesions. You'll agree you wouldn't have missed it!)

I agree with your self assessment ("almost sure I don't have it"), but I have already told you how to be certain:  have a syphilis blood test. As already mentioned, it is likely your wife has been tested and negative as well.

Threads are closed after two follow-up exchanges, so you have one more coming. If you would like to be tested and then return to let me know about the result, feel free -- but I will have no other advice or comment until then. Your test will be negative.